Patent Application
20150010672
Embodiments of the present invention relate generally to a method for improving bowel health by administering a treated bran or hydrolyzate product, in particular the product has about 50% to about 93% by weight arabinoxylans.
It is clear that individuals on a normal Western diet do not consume enough dietary fiber. In the United States, adult men and women, on average, consume an inadequate 17.8 and 14.1 g/d, respectively (1). This is in comparison with recommendations of 38 and 25 g/d, respectively (2-3).
There are numerous adverse effects of inadequate dietary fiber intake. In addition to constipation, recent literature ties insufficient dietary fiber consumption with increased risk of colon cancer (4-5), type 2 diabetes (6-7), heart disease (8), obesity (9), and inflammatory bowel disease (10). Three of these diseases (i.e., cancer, diabetes, and heart disease) are among the top 10 leading causes of death in the United States (11).
The solubility of a dietary fiber can facilitate the inclusion of fiber into food and beverage products, because soluble fiber can be more easily incorporated into food formulations without detrimental effects on sensory properties, while insoluble dietary fibers generally produce grittiness and reduced sensory profile.
From a nutritional standpoint, dietary fibers with a slow fermentation rate may be most desirable. A slow fermentation rate has two major benefits. First, slow fermentation minimizes bloating due to low initial production of gas by the gut microbiota; gases produced have time to be absorbed and exhaled before colonic distension occurs. Second, slow fermentation allows for high short chain fatty acid (“SCFA”) production by the gut microbiota in the distal colon. Slowly fermentable fiber prevents the build-up of toxic metabolites, such as phenols and ammonia, which accumulate due to bacterial fermentation of protein when fermentable carbohydrate is not available. Slowly fermentable fiber creates an environment that is less favorable for the development of colonic diseases such as colon cancer and ulcerative colitis.
Unfortunately, most dietary fibers available today are either rapidly fermenting or poorly fermenting. Rapidly fermenting soluble dietary fibers, such as pectin, fructooligosaccharides (FOS), and β-glucan ferment rapidly in the cecum and proximal colon, leaving little carbohydrate substrate for bacteria in distal regions of the colon (12), while insoluble dietary fibers such as cellulose and other intact cell wall polysaccharides do not substantially ferment, but contribute mainly to stool bulking and pass through the colon largely intact.
Thus, dietary fiber should be soluble to facilitate its use in foods, and ferment slowly and completely. This advantageously provides benefits over existing dietary fibers, because it is easier to incorporate into foods, it does not contribute to excessive bloating and it induces high SCFA production in the distal colon for the prevention of colonic disease.
Cereal brans present an interesting source of dietary fiber because they can be obtained cheaply, contain high levels of dietary fiber, and their consumption has been associated with lower risk of disease (16). Unfortunately, cereal brans generally are poorly fermented (17), and thus are not desirable dietary fibers for stimulating a healthy colonic production of SCFAs.
While pre-existing approaches for treating and preventing disease by consuming fiber products generally have been adequate, these approaches have not been satisfactory in all respects, namely that the fiber products are either poorly fermented and do not induce substantial SCFA production in the distal colon, or that the fiber products result in excessive bloating and gas due to rapid fermentation in the proximal colon.
The embodiments described herein provide a method for improving bowel health by increasing short chain fatty acid concentration in the colon of a mammal, including administering to the mammal a composition having about 0.1 grams to about 50 grams of a treated bran product. After administration, the treated bran product results in an increased short chain fatty acid production during fermentation in the colon as compared to untreated bran fermented in the colon.
According to certain embodiments of the present invention shown in
Certain other embodiments of the present invention provide that, after administration of the treated bran product, the carbohydrate content in the treated bran product is fermented more than untreated bran during fermentation. In still other embodiments, the carbohydrate content is reduced to less than 10% of the initial carbohydrate content during such fermentation.
Also according to certain embodiments of the present invention, the treated bran product is made from corn bran and, after administration, the treated corn bran product produces a lower amount of gas during the first four hours of fermentation as compared to treated rice bran and wheat bran, wherein the treated rice bran and wheat bran are treated in the same manner as the treated corn bran. The treated corn bran product has a slow rate of fermentation and is a fermentable substrate in the distal colon. The treated corn bran product results in an increased short chain fatty acid production during fermentation in the colon as compared to treated rice bran and wheat bran. The treated corn bran product includes about 50% to about 93% by weight arabinoxylans.
Certain other embodiments of the present invention, shown in
Certain embodiments of the present invention provide a method for improving bowel health by increasing short chain fatty acid concentration in the colon of a mammal, in particular in the distal colon of a human, including administering to the mammal a composition having about 0.1 grams to about 50 grams of a bran hydrolyzate product. After administration, the bran hydrolyzate product results in an increased short chain fatty acid production during fermentation in the colon, particularly in the distal colon, as compared to untreated bran fermented, alkali-soluble wheat bran, and alkali-soluble rice bran in the colon.
According to certain embodiments of the present invention, the bran hydrolyzate product is produced by a method including contacting a bran with a first alpha-amylase enzyme and a first protease enzyme sufficient to form an enzyme modified bran; deactivating the first alpha-amylase and protease enzymes; contacting the enzyme modified bran with an alkaline and hydrogen peroxide solution for a time sufficient to produce an alkali-soluble bran; separating the alkali-soluble bran from the alkaline and hydrogen peroxide solution; isolating the alkali-soluble bran using a first and a second precipitation step to produce an ethanol precipitated alkali-soluble bran, wherein the first ethanol precipitation step uses a first ethanol solution and the second ethanol precipitation step uses a second ethanol solution having an ethanol concentration higher than the first ethanol solution; contacting the ethanol precipitated alkali-soluble bran with an endoxylanase sufficient to form a bran hydrolyzate; deactivating the endoxylanase; and isolating the bran hydrolyzate using the first and second precipitation step to produce a bran hydrolyzate product. According to certain embodiments, the bran is corn, wheat, rice, sorghum, or any combination thereof.
Another embodiment of the present invention provides that the bran hydrolyzate product is made from corn bran and, after administration, the corn bran hydrolyzate product produces a low amount of gas during the first four hours of fermentation as compared to untreated rice bran and wheat bran, and an increased short chain fatty acid production during fermentation in the colon as compared to untreated bran fermented in the colon. Moreover, in certain embodiments the corn bran hydrolyzate product produces a low amount of gas during the first four hours of fermentation as compared to rice bran hydrolyzate product processed by the same method as the corn bran hydrolyzate product. The corn bran hydrolyzate product includes about 50% to about 93% by weight arabinoxylans.
A certain embodiment of the present invention includes a bran hydrolyzate product that is made from wheat bran and, after administration, the wheat bran hydrolyzate product produces a low amount of gas during the first four hours of fermentation as compared to untreated wheat bran. Moreover, in certain embodiments, the wheat bran hydrolyzate product produces a low amount of gas during the first four hours of fermentation as compared to a corn bran hydrolyzate product and a rice bran hydrolyzate product, which have been processed by the same method as the wheat bran hydrolyzate product. The wheat bran hydrolyzate product includes about 50% to about 93% by weight arabinoxylans.
In still another embodiment, the corn bran hydrolyzate product has a lower viscosity and a lighter color as compared to the wheat bran hydrolyzate product.
Another embodiment provides for a food or beverage product made from the methods described herein. In yet another embodiment, the present invention provides a soluble fiber supplement for food, beverages, or feed made from the methods described herein.
Embodiments of the present invention described herein provide a method for improving bowel health by increasing short chain fatty acid concentration in the colon of a mammal including administering to the mammal of a treated bran product or a hydrolyzate bran product and, after administration, the treated or hydrolyzate bran product results in an increased SCFA production during fermentation in the colon as compared to untreated bran fermented in the colon. Certain embodiments of the present invention provide a low initial product of gas during fermentation, which minimizes bloating and contributes to an improved amount of SCFA in the distal regions of the colon.
Fiber fermentation in the colon produces SCFAs (e.g., acetic, propionic, and butyric acids) that contribute to colon health by increasing blood flow, improving mineral and water absorption by maintenance of low luminal pH. Moreover, SCFAs are the main products of anaerobic dietary bran fermentation, and exhibit numerous trophic effects on the colonic environment. Because SCFAs reduce colonic pH, they inhibit the growth of opportunistic, pathogenic bacteria (33), decrease the activity of co-carcinogenic enzymes such as glucuronidases, glycosidases, and 7α-hydroxylases (34-35), increase mineral absorption (36), and reduce ammonia absorption by maintaining ammonium in its less diffusible, ionic form (37).
SCFAs themselves also have a number of physiological effects. Acetate and propionate are readily absorbed by diffusion, and, as the major anions in the colon, absorption is facilitated by anion exchange with sodium and potassium (38). Once absorbed, acetate and propionate are taken up by the liver or peripheral tissues. Acetate can be used for the synthesis of long chain fatty acids, glutamine, glutamate, and beta-hydroxybutyrate (17); acetate is also a major substrate for cholesterol synthesis (39). Indeed, when subjects were fed 25 g/d of lactulose, a highly fermentable, highly acetogenic synthetic disaccharide, significant increases in serum total, low-density-lipoprotein cholesterol, and apolipoprotein B concentrations were observed (40). Propionate appears to counter the hypercholesterolemic effects of acetate (41). In rats, propionate was shown to decrease cholesterol synthesis (42-43). Propionate is also a substrate for hepatic gluconeogenesis (39), and therefore may influence glucose metabolism and postprandial blood glucose levels. Butyrate is utilized mainly by colonic epithelial cells for energy (17). Butyrate also influences cell differentiation and proliferation (44), and has therefore been implicated in the prevention of colon cancer (45). In vitro studies also have shown that butyrate suppresses the inflammatory response by inhibiting NF-κB activation (46), and patients treated with butyrate enemas have shown decreased inflammation related to a reduction in the number of macrophages positive for NF-κB (47).
Along with SCFAs, fiber fermentation by the colonic microbiota in the colon produces gas as an additional by-product. Depending on the source of dietary fiber, gas may be produced rapidly or over a sustained period of time. Large amounts of gas production during the first four hours of fermentation often cause the particularly troublesome problems of bloating, pain, and abdominal distension. Conversely, sustained gas production, such as over a 12-24 hour period, is not associated with bloating because the gases have time to be absorbed and exhaled before colonic distension occurs.
The embodiments described herein provide a method for improving bowel health by increasing short chain fatty acid concentration in the colon of a mammal including administering to the mammal a composition having about 0.1 grams to about 50 grams, about 0.1 to about 40 grams, about 0.1 grams to about 30 grams, about 0.1 grams to about 20 grams, about 0.1 to about 10 grams, and about 0.1 to about 5 grams of a treated bran product. After administration, the treated bran product results in an increased short chain fatty acid production during fermentation in the colon as compared to untreated bran fermented in the colon.
Bran, as used herein, includes the edible outer layer of an edible cereal grain, such as, but not limited to, corn, wheat, rice sorghum, or any combination thereof. The bran is a cereal bran. Corn bran is described herein as maize bran and is abbreviated as “MB” or indicated by the capital letter “C.”
An untreated bran is bran that has not been processed according to the methods described herein and as illustrated by
A treated bran is bran that has been processed by the methods described herein and as illustrated by
A bran hydrolyzate product is the final and administered product processed by the methods described herein and as illustrated by
According to certain embodiments of the present invention as illustrated in
The enzyme modified bran is contacted with alkaline and hydrogen peroxide solution for a time sufficient to produce an alkali-soluble bran. In particular, the enzyme modified bran is first suspended in 1 M sodium hydroxide and 30% hydrogen peroxide is then slowly added to the mixture under constant mixing at 60° C. The quantities of the bran, sodium hydroxide, and 30% hydrogen peroxide varies depending on the quantity of bran being treated, for example and not limitation, 50 grams of enzyme modified bran is suspended in 1 L of sodium hydroxide and 42 ml of 30% hydrogen peroxide is added thereto. The enzyme modified bran and alkaline-hydrogen peroxide mixture is stirred for about four hours and yields alkali-soluble bran, which then is separated using conventional methods such as, but not limited to, centrifuging at 10,000×g for 10 minutes.
The alkali-soluble bran is isolated using conventional methods such as, but not limited to, ethanol precipitation. In particular, ethanol is added to the alkali-soluble corn bran and held overnight at 4° C. to liberate the ferulic acid, which is siphoned off with the ethanol. The precipitated alkali-soluble corn bran then is washed with 80% ethanol, anhydrous ethanol, and acetone. The resulting alkali-soluble corn bran is dried, followed by the addition of ethanol to the supernatant. The alkali-soluble bran then is dried to remove the solvent and then dried again to purify the alkali-soluble corn bran using conventional drying methods, such as, but not limited to, air drying or drying in an oven.
The alkali-soluble bran undergoes a second enzymatic treatment as shown in
The combination of enzymatic and alkaline-hydrogen peroxide treatments pursuant to the method described above and shown in
Also beneficially, the treated corn bran results in surprisingly increased SCFA production during fermentation in the colon as compared to treated rice and wheat brans (e.g., the treated rice and wheat brans were treated using the same method as the treated corn bran).
Moreover, the treated corn bran product produces a lower amount of gas during the first four hours of fermentation as compared to treated rice bran and wheat bran, wherein the treated rice bran and wheat bran are treated in same manner as the treated corn bran. In certain other embodiments, the treated corn bran product produces a lower amount of gas during the first four hours of fermentation as compared to untreated soluble fibers.
The fermentation profile of the treated corn bran product indicates that the treated corn bran is highly fermentable and is slower to ferment as compared to similarly treated rice and wheat brans. The treated corn bran product includes from about 73% to about 93% by weight arabinoxylans
According to an embodiment of the invention, the bran is processed by the method shown in
Unlike the method shown in
In particular, the alkali-soluble bran is rehydrated 3% w/w water. Then 95% ethanol is added to the water and alkali-soluble bran mixture in an amount sufficient to achieve a concentration of 40% ethanol under continuous stirring for 30 minutes and kept in a refrigerator at 4° C. overnight. The 40% ethanol, bran, and water mixture is then centrifuged for thirty minutes at 6° C., which provides a precipitate that is insoluble in 40% ethanol and a supernatant. Ethanol 95% is added to the supernatant to obtain a concentration of 60% ethanol by volume under continuous stirring for 30 minutes and is refrigerated overnight. The 60% ethanol mixture is then centrifuged at 10,000×g for thirty minutes at 6° C. to yield a supernatant, which is discarded, and a precipitate that is insoluble in 60% ethanol. The first ethanol solution has a concentration of 40%, 50%, or 60% by volume ethanol depending on the bran. The second ethanol solution has a concentration higher than the first ethanol solution and has a concentration of 60%, 70%, 80%, or 90% by volume. The ethanol is removed by conventional methods, such as, but not limited to air drying to yield a treated bran product, which is an ethanol precipitated alkali-soluble bran.
According to certain embodiments described above and shown in
Certain embodiments of the present invention provide a method for improving bowel health by increasing short chain fatty acid concentration in the colon of a mammal including administering to the mammal a composition having about 0.1 grams to about 50 grams, about 0.1 to about 40 grams, about 0.1 grams to about 30 grams, about 0.1 grams to about 20 grams, about 0.1 to about 10 grams, and about 0.1 to about 5 grams of a bran hydrolyzate product are shown in
According to certain embodiments of the present invention, the bran hydrolyzate product is produced by a method similar to the methods described in
According to the method shown in
After the endoxylanase treatment, the bran hydrolyzate is isolated using the first and second precipitation step to produce a bran hydrolyzate product. In particular, the bran hydrolyzate fraction underwent a graded ethanol precipitation which involves rehydrating 10 grams of the hydrolyzate fraction 3% w/w water. Then 95% ethanol is added in an amount to achieve 40% concentration of ethanol to the water and hydrolyzate mixture under continuous stirring for 30 minutes and kept in a refrigerator at 4° C. overnight. The mixture is then centrifuged for thirty minutes at 6° C., which provides a precipitate that is insoluble in 40% ethanol and a supernatant. The precipitate is discarded. Ethanol 95% is added to the supernatant to obtain a concentration of 60% ethanol by volume under continuous stirring for 30 minutes and is refrigerated overnight. The 60% ethanol mixture is then centrifuged at 10,000×g for thirty minutes at 6° C. to yield a supernatant and precipitate that is insoluble in 60% ethanol. The ethanol is removed from the precipitate according to conventional methods, such as, drying to yield a bran hydrolyzate product that, after administration to a mammal, the bran hydrolyzate product results in an increased short chain fatty acid production during fermentation in the colon as compared to untreated bran fermented in the colon.
An embodiment of the invention provides that the bran hydrolyzate product is made from corn bran and, after administration, the corn bran hydrolyzate product produces a low amount of gas during the first four hours of fermentation as compared to untreated rice bran and wheat bran. The corn bran hydrolyzate product includes about 50% to about 93% by weight arabinoxylans and has a degree of polymerization around 450.
A certain embodiment of the present invention includes a bran hydrolyzate product is made from wheat bran and, after administration, the wheat bran hydrolyzate product produces a low amount of gas during the first four hours of fermentation as compared to untreated wheat bran. The wheat bran hydrolyzate product includes about 50% to about 93% by weight arabinoxylans.
The corn bran hydrolyzate has improved viscosity and characteristics as compared to a wheat bran hydrolyzate. For example, the corn bran hydrolyzate has a lower viscosity and a lighter color as compared to the wheat bran hydrolyzate product.
The present invention provides methods of treating and preventing disorders, disease conditions, particularly diseases of the colon, in a mammal and particularly in a human, by oral administration of a therapeutically-effective amount of a composition including a treated bran product or bran hydrolyzate product to an individual in need of treatment or prophylaxis. The result of treatment can be partially or completely alleviating, inhibiting, preventing, ameliorating and/or relieving the disorder, condition or one or more symptoms thereof. Administration is by oral ingestion. An individual in need of treatment or prophylaxis includes those who have been diagnosed to have a given disorder or condition and to those who are suspected, for example, as a consequence of the display of certain symptoms, of having such disorders or conditions.
References cited herein are incorporated by reference herein in their entirety to indicate the state of the art as of their publication or filing date and it is intended that this information can be employed herein, if needed, to exclude specific embodiments that are in the prior art.
As used herein, “comprising” is synonymous with “including,” “containing,” or “characterized by,” and is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. As used herein, “consisting of” excludes any element, step, or ingredient not specified in the claim element. As used herein, “consisting essentially of” does not exclude materials or steps that do not materially affect the basic and novel characteristics of the claim. In each instance herein any of the terms “comprising”, “consisting essentially of” and “consisting of” may be replaced with either of the other two terms. The invention illustratively described herein suitably may be practiced in the absence of any element or elements, limitation or limitations which is not specifically disclosed herein.
The following examples are provided for illustration and not limitation.
The tested samples consisted of finely ground corn bran from Bunge Milling Inc. in St. Louis, Mo., and heat-stabilized rice bran and wheat bran were obtained from a local market. Rice bran and wheat bran were finely ground in a cyclone mill to pass through a 0.8 mm screen. Bran was partially defatted with two volumes of hexane using a bran:hexane ratio of 1:7 weight/volume for 30 minutes in an Erlenmeyer flask. After stirring, the bran was allowed to settle for about 5 to 10 minutes and the hexane was decanted through a vacuum flask, which collected the bran on Whatman No. 2 filter paper. The bran was allowed to air dry.
Bran was suspended in water in an amount of 1:9 w/w bran to water, and the pH was adjusted to 7.0. Under constant stirring, the mixture was boiled, and then cooled to 95° C. and 4 ml of heat stable alpha-amylase, which is commercially available from Sigma-Aldrich Corp., St. Louis, Mo., was added. The starch was hydrolyzed at about 90 to 95° C. for 30 min, and then the mixture was cooled in an ice bath to 50° C. The pH was adjusted to 6.0, and 5 ml of neutral protease, which is commercially available as Sigma P1236 protease from Bacillus amyloliquefaciens from Sigma-Aldrich Corp., St. Louis, Mo., were added. Protein was hydrolyzed at 50° C. for 4 h, and then the mixture was brought to a boil to inactivate enzymes, cooled in an ice bath, and the pH adjusted to 7.0. The slurry was centrifuged at 10,000×g for 10 minutes. The residue was washed 3 times with water, dried in a forced draft oven at 40° C. for 48 hours, ground in a cyclone mill, and passed through a 0.8 mm screen to yield enzyme modified bran fiber. These steps produced a destarched and proteolyzed enzyme modified bran.
The enzyme modified bran then underwent an alkaline-hydrogen peroxide method (23-24), with modifications. Fifty grams of the enzyme-treated bran from above were suspended in 1 L of 1 M sodium hydroxide. Under constant mixing at 60° C., 42 ml of 30% hydrogen peroxide was slowly added to the mixture, which was stirred for a total of 4 h, and then centrifuged (10,000×g for 10 min), followed by an ethanol precipitation involving the addition of 3 volumes of 95% ethanol to the supernatant. The mixture was held overnight at 4° C., and then the aqueous ethanol portion, containing the liberated ferulic acid, was siphoned off, discarded, and yield a precipitated material.
The alkali-soluble bran underwent a second enzymatic treatment involving suspending the alkali-soluble bran in water in an amount of 1:9 w/w bran to water, and the pH was adjusted to 7.0. Under constant stirring, the mixture was boiled, and then cooled to 95° C. and 4 ml of heat stable alpha-amylase, which is commercially available from Sigma-Aldrich Corp., St. Louis, Mo., was added. The starch was hydrolyzed at about 90 to 95° C. for 30 minutes, and then the mixture was cooled in an ice bath to 50° C. The pH was adjusted to 6.0, and 5 ml of neutral protease, which is commercially available as Sigma P1236 protease from Bacillus amyloliquefaciens from Sigma-Aldrich Corp., St. Louis, Mo., were added. Protein was hydrolyzed at 50° C. for 4 h, and then the mixture was brought to a boil to inactivate enzymes, cooled in an ice bath, and the pH adjusted to 7.0. The slurry was centrifuged at 10,000×g for 10 minutes. The residue was washed 3 times with water, dried in a forced draft oven at 40° C. for 48 hours, ground in a cyclone mill, and passed through a 0.8 mm screen to yield enzyme treated bran fiber.
The precipitated material was washed with 80% ethanol, 95% ethanol, and acetone. The resulting powder was air dried until no solvent could be detected by odor, and then further dried in an oven at 40° C. for 24 h.
In vitro digestion is a simulated upper gastrointestinal digestion, i.e. mouth, stomach, and small intestine, which was carried out by a method described in Lebet et al. (25), except pancreatin was suspended in phosphate buffer (20 mM, pH 6.9, containing 10 mM calcium chloride) instead of water, and the concentrations of pepsin and pancreatin were increased by factors of 10 to enhance breakdown of digestible components. In particular, the in vitro digestion was performed when six g of sample were suspended in 42 ml of phosphate buffer (20 mM, pH 6.9, containing 10 mM sodium chloride). After temperature equilibration at 37° C. for about 10 to 20 min, 1 ml of salivary alpha-amylase (28.4 U/ml in 1 mM calcium chloride) was added, and the mixture shaken using LabLine, which is commercially available from EnvironShaker, Melrose Park, Ill., at 150 rpm and 37° C. for 15 minutes. The pH was adjusted to 2.0±0.1 with 6 N HCl, 1 ml of pepsin (51 U/ml in 15 mM HCl) was added, and the mixture shaken at 150 rpm and 37° C. for 30 min. The pH was adjusted to 6.9±0.1 with 6 N sodium hydroxide, 1 ml of pancreatin (5 mg/ml in phosphate buffer from above) was added, and the mixture shaken at 150 rpm and 37° C. for 90 min. Samples that had not been previously cooked (i.e., the raw bran starting materials) were submerged in boiling water for 20 minutes to facilitate digestion prior to salivary alpha.-amylase treatment. Following digestion, the suspensions were dialyzed using a membrane, which is commercially available as Spectra/Por 3 from Spectrum Labs, Rancho Dominguez, Calif., against distilled water for 24 hours with 3 changes of distilled water, and then freeze-dried using a freeze drier, which is commercially available from VirTis, Gardiner, N.Y.).
In vitro fermentation simulates lower gastrointestinal fermentation, i.e. fermentation in the colon, which was carried out by a batch fecal fermentation method described in Lebet et al. (26), with some modifications to estimate the behavior of each fiber fraction in the colon. A sufficient sample such that each tube contained 50 mg of carbohydrate (neutral sugars and uronic acids) was weighed into each of 5 serum tubes for each replicate (i.e. one tube per replicate for each sampling period: 0, 4, 8, 12, and 24 hours). Fermentations were carried out in duplicate. Anaerobic carbonate-phosphate buffer was prepared pursuant to the methods described in Durand et al., 1988, and then sterilized by autoclaving for 20 minutes at 121° C. Immediately following autoclaving, 0.25 mg/L of cysteine hydrochloride was added as a reducing agent, and carbon dioxide was bubbled through the buffer. During use, a constant stream of carbon dioxide was bubbled through the buffer to maintain anaerobiosis. Four ml of this buffer were added, along with 100 μl of OXYRASE®, which is commercially available as OXYRASE® for Broth from Oxyrase, Inc., in Mansfield, Ohio, to each tube. The OXYRASE® was added to scavenge any residual oxygen, and the tubes were sealed anaerobically (by flushing headspace with carbon dioxide) with a rubber stopper and metal crimp cap, and placed at 4° C. overnight to hydrate.
The next morning, feces were collected from 3 healthy volunteers consuming unspecified and varied diets and who had not taken antibiotics in the last 3 months. Once feces were collected, they were kept on ice and tightly sealed in plastic with air expelled and used within 2 hours. The feces were combined and homogenized with 3 parts sterile anaerobic carbonate-phosphate buffer (prepared and maintained as described above) and then filtered through 4 layers of cheesecloth. Tubes were opened and 1 ml of filtrate was used to inoculate each tube under constant carbon dioxide flushing. The tubes were then re-sealed and incubated at 37° C. with gentle shaking. At pre-determined time intervals (0, 4, 8, 12, or 24 hours), the tubes were removed from the water bath, and total gas volume was measured by inserting a needle attached to a graduated syringe through the rubber stopper. The tubes were then opened, and microbial activity was halted by the addition of 0.4 ml of 2.75 mg/ml copper sulfate (containing 12.5 mg/ml of myo-inositol, as an internal standard for residual carbohydrate analysis). The pH was recorded, and a 0.4 ml aliquot was combined with 0.1 ml of 5% phosphoric acid (containing 50 mM 4-methyl valeric acid, as an internal standard for SCFA analysis), mixed with a vortex mixer, and frozen (−40° C.) for SCFA quantification. The remainder of the reaction mixture was also frozen and then freeze-dried for monosaccharide analysis.
Moisture content of samples was determined by loss in weight upon drying at 105° C. for 16 hours. Protein was determined using a nitrogen analyzer commercially available as a Perkin Elmer Series II Nitrogen Analyzer, Model 2410, with a conversion factor from % nitrogen to % protein of 6.25. Starch was determined using an assay kit, which is commercially available as a Total Starch (AA/AMG Method) kit from Megazyme, Wicklow, Ireland. Total dietary bran was determined as the sum of neutral sugars, uronic acids, and lignin, according to AACC International Official Method 32-25 (28), except the procedure was modified to accommodate a smaller sample size (50 mg), and, because the starch content was known, the digestion procedure was skipped, and the glucose contributed by starch was subtracted from the total glucose content to obtain non-starch glucose. In preliminary experimentation, these modifications were found to give values for non-starch glucose and total dietary bran that were statistically indistinguishable from those using the method as published (data not shown). Each of these analyses was performed before and after in vitro upper-gastrointestinal digestion.
Additional characterization of the alkali-soluble fractions after in vitro upper-gastrointestinal digestion was performed using size-exclusion chromatography (SEC) and 1H-NMR spectroscopy. For the chromatography, samples (2.0 mg/ml) were dissolved in 0.2% (w/v) sodium azide at 50° C. for 1 hour, and filtered (5 μm cut-off). The filtered sample was injected onto a SEC system consisting of a pump commercially available from Varian in Walnut Creek, Calif., an injection valve commercially available from Rheodyne in Rohnert Park, Calif. with a 500 μL sample loop, a column (50 cm×2 cm) packed with SEPHACRYL® S-500 commercially available from GE Healthcare Life Sciences in Piscataway, N.J. at room temperature, and a refractive index detector commercially available from Varian in Walnut Creek, Calif. Mobile phase was 0.2% sodium azide at 1.3 ml/min. Data were collected using GALAXIE™ software commercially available from Varian in Walnut Creek, Calif. Molecular weight was estimated using the retention times of known pullulan standards. Normalized peak areas were calculated by dividing the area of the peak of interest by the total area of all peaks.
Samples for 1H-NMR spectroscopy were prepared by dissolving samples in deuterium oxide (10 mg/ml) for 8 hours at room temperature, followed by freeze-drying. The dissolving and freeze-drying steps were repeated twice more, and then spectra were recorded on a 300 MHz spectrometer at 85° C. Sixty-four pulses were collected, with an acquisition time of 1.7 seconds, a relaxation delay of 2 seconds, and a pulse angle of 45°. Partial structural assignments of the peaks were made by comparison with previously published data (29-32).
For SCFA and branched chain fatty acid (BCFA) quantification, 0.4 ml of fermentation slurry was combined with 0.1 ml of 5% phosphoric acid (containing 50 mM 4-methyl valeric acid, as an internal standard), mixed with a vortex mixer, and allowed to rest for 30 min. Samples were then centrifuged at 13,000 rpm for 10 minutes, and a 4 μl aliquot was injected onto a HP 5890 GC equipped with a NUKOL™ capillary column, which is commercially available as 30 m×0.25 mm ID with 0.25 μm bonded phase from Supelco in Bellefonte, Pa., under conditions defined by the manufacturer.
Ammonia was determined using an enzymatic method known as the glutamate dehydrogenase/NADH/2-oxoglutarate method, which is commercially available from Boehringer in Mannheim, Germany, and residual carbohydrates (neutral sugars and uronic acids) were measured in freeze-dried fermentation residues using AACC International Official Method 32-25 (28) with the modifications described above (see Sample Analyses).
SAS software (version 9.1, SAS Institute, Cary, N.C.) was used to calculate statistical differences, which were defined as P<0.05. SCFA, see
The combination of enzymatic and alkaline-hydrogen peroxide treatment was sufficient to remove at least 65% of the protein and 90% of the starch in the alkali-soluble fractions from corn, rice, and wheat brans, see Table 1. A higher percentage of the alkali-soluble fraction was found in corn bran compared to rice and wheat brans. The alkali-soluble fraction from corn bran was also the highest in total dietary bran and contained the least amount of non-starch glucose. The dietary bran composition of corn, rice, and wheat bran alkali-soluble fractions revealed that each contained mostly arabinoxylan, as these two monosaccharides (arabinose and xylose) represented the majority of neutral monosaccharides in the fractions.
aMean ± standard deviation; n = 2.
bN × 6.25.
cND, none detected.
dExpressed as anhydrous sugars.
eNon-starch glucose.
The protein content of all samples remained roughly constant before, see Table 1, and after, see Table 2, in vitro digestion, indicating that the in vitro digestion procedure was ineffective at removing protein. The alkali-soluble fractions were extensively treated with protease during the extraction procedure prior to in vitro digestion, which may explain why these samples did not show a further decrease in protein during in vitro digestion; however, this does not explain why the bran starting materials did not decrease in protein content. Lebet et al. (25) described the difficulty in removing digestible components during in vitro digestion. The breakdown of digestible components was improved by increasing the levels of digestive enzymes used by a factor of 10 compared to the referenced method (25). The contaminating starch, not protein, has the greatest confounding effect on fermentation profiles. The enzymatic and alkaline-hydrogen peroxide treatment was able to remove most of the starch from all samples, see Table 2.
4.40 ± 0.07b
aN × 6.25.
bMean ± standard deviation; n = 2.
cND, none detected.
dExpressed as anhydrous sugars.
eNon-starch glucose.
The alkali-soluble fraction from corn bran produced significantly more SCFAs, which was calculated as the sum of acetate, propionate, and butyrate, than other samples tested, see Table 3. This indicates that the corn sample was highly fermentable, with efficient conversion of carbohydrate to SCFAs by the fecal bacteria. This fraction also displayed a much more linear shaped profile of SCFA production over the 24 hour fermentation period compared to the other samples, see
aMeans within row with different capital-letter superscripts are significantly different (p < 0.05); n = 2;
bSM, starting material; AS, alkali-soluble; ND, none detected;
cSCFA and BCFA expressed as μmol/mg carbohydrate with blank subtracted out of the data;
dammonia expressed as μmol/sample tube.
In vivo, a slow fermentation rate may be particularly beneficial (14). Once digesta reaches the distal colon, much of the fermentable carbohydrate has been fermented. Thus, the distal colon is chronically low in SCFAs, and exhibits higher levels of undesirable metabolites such as ammonia and phenol (13). A slowly fermentable dietary bran would help counter this gradient, and maintain more healthy colonic conditions in the distal colon.
The alkali-soluble fraction from corn bran was particularly propiogenic, producing significantly more of this SCFA after 24 hours of fermentation than other samples, see Table 3. This is noteworthy because dietary brans that have high production of propionate may help reduce cholesterol (43). Among alkali-soluble fractions of the three brans, butyrate concentrations were approximately the same.
When fermentable carbohydrate is exhausted in the large intestine, bacteria begin to ferment protein as a source of energy. Bacterial fermentation of protein is commonly called putrefaction, which results in a mixture of metabolites including hydrogen sulfide, phenolic, indolic, and N-nitroso compounds, BCFAs, amines, and ammonia (15). Some of these products are particularly undesirable. For instance, hydrogen sulfide blocks proper butyrate oxidation and utilization by the colonic epithelial cells and has been implicated in the pathogenesis of ulcerative colitis (48-49), phenol can react with nitrite (also present in the lumen of the colon) in vitro to produce the mutagenic compound p-diazoquinone (50), and ammonia induces histological damage to distal colonic mucosa (51).
BCFAs and ammonia were measured as markers of protein putrefaction. The alkali-soluble fraction from corn bran produced more BCFAs, calculated as the sum of iso-butyrate and iso-valerate, than any other sample, see Table 3. Despite producing the highest level of BCFAs during fermentation, the alkali-soluble fraction from corn bran resulted in among the lowest of the test materials ammonia production during fermentation; alkali-soluble fractions resulted in low ammonia production during fermentation, while the bran starting materials produced higher levels, see Table 3.
The SCFA data revealed that the alkali-soluble fraction from corn bran fermented slowly and completely, while the alkali-soluble fractions from rice and wheat brans fermented more rapidly initially, suggesting that these brans were either incompletely fermented or the bacteria were less efficient at converting them to SCFAs. Thus, one would have expected the highest level of residual carbohydrate in the alkali-soluble fraction from corn bran at t=12 hours, accompanied by the lowest level of carbohydrate in this sample at the final time (t=24 hours). Instead, of the alkali-soluble fractions, the fraction from wheat bran showed the highest level of residual carbohydrate at both 8 hours and 12 hours of fermentation, and all samples showed (nearly) complete fermentation after 24 hours.
Because arabinoxylans consist, basically, of a xylose backbone with arabinose side chains (20), the arabinose to xylose ratio is a rough estimate of the degree of branching.
It is possible that the unbranched regions of wheat arabinoxylans are metabolized, the remaining oligosaccharides are quite densely branched, providing resistance to hydrolysis by bacterial arabinases due to steric hindrance. This would hinder fermentation, which as shown in
The alkali-soluble fraction from corn bran contained a less complex SEC profile than the fractions from rice and wheat brans with the former showing a single peak (normalized peak area, 98.5%) that crested at 49 minutes (˜500 kDa), see
The finding that alkali-soluble rice and wheat arabinoxylans molecular weight distributions each showed two fractions may explain their surprisingly high initial productions of SCFAs, followed by a slower rate of production, see
The portion of the 1H-NMR spectrum for each of the alkali-soluble arabinoxylans where the anomeric protons of the α-linked arabinose units in an arabinoxylan resonate is shown in
Each spectrum contained additional resonances that may be attributed to the anomeric hydrogens of arabinose residues, including peaks between 5.00 and 5.20 and at 5.53 ppm. The resonance at 5.53, which is present in the alkali-soluble fractions from corn bran and rice bran, may be attributed to a disaccharide side chain with the structure: β-D-Xylp-(1→2)-α-L-Araf linked to O-3 of Xylp on the main chain (29). For this side chain to be present, the 1H-NMR spectrum must also show a resonance corresponding to the anomeric hydrogen of the Xylp residue, which occurs at 4.56 ppm (55). The alkali-soluble fraction from corn bran contained a clear resonance at this position, and, although the fraction from rice bran did not, it may have been buried under other peaks present in this region (data not shown). The alkali-soluble fraction from corn bran contained the highest proportion of this disaccharide side chain. The presence of this side chain, particularly if it were evenly distributed along the xylan backbone, may be a contributing factor to the slower fermentation rate of this sample, through the difficulty in hydrolyzing the unusual β(1→2) linkage.
Structural assignments for the resonances between 5.00 and 5.20 ppm were more difficult to define. Literature data suggest that these resonances represent substituted arabinose units (multi-unit branches or branched branches) (56-58). The peak at 5.00 ppm in particular has been shown in a number of previous reports (59-61), but has not been specifically identified. The peaks at 5.19 and 5.12 ppm, present in the alkali-soluble fraction from wheat bran, have also been previously found in rye bran after barium and potassium hydroxide extraction (60) and in barley after barium hydroxide extraction (62), but were not defined.
Because the 1H-NMR spectra suggest that not all arabinose units are involved in single unit branches, the equations of Roels et al. (63) for calculating the distribution of un-, mono-, and disubstituted xylose residues on arabinoxylan, are not valid; however, from the quantitative integrals of the resonances at 5.40, 5.30, and 5.23, the ratio of monosubstituted to disubstituted xylose residues containing single-unit arabinose branches could be calculated. For the alkali-soluble fractions from corn, rice, and wheat brans, this ratio was 1.70, 1.44, and 0.85. This indicates that the alkali-soluble fraction from wheat bran contained a higher proportion of disubstituted xylose residues and, therefore more unsubstituted regions, which was expected from the parabolic relationship observed in arabinose to xylose ratio during fermentation, see
Gas production from in vitro fecal fermentation of water-soluble wheat and rice arabinoxylans and alkali-soluble corn, wheat and rice arabinoxylans is shown in
Moreover, the fermentation rate of the treated corn bran is linear with a high production of SCFAs during 24 hours of in vitro fermentation. These unique characteristics are not present for the same from treated rice and wheat bran.
Finely ground corn bran was from Bunge Milling (St. Louis, Mo.), and heat-stabilized rice bran and wheat bran were obtained from a local market. Rice bran and wheat bran were finely ground in a cyclone mill to pass through a 0.8 mm screen. Bran was partially defatted with two volumes of hexane using a bran:hexane ratio of 1:7 weight/volume for 30 minutes in an Erlenmeyer flask. After stirring, the bran was allowed to settle for 5 to 10 minutes and the hexane was decanted through a vacuum flask, which collected the bran on Whatman No. 2 filter paper. The bran was allowed to air dry.
Bran was suspended in water in an amount of 1:9 w/w bran to water, and the pH was adjusted to 7.0. Under constant stirring, the mixture was boiled, and then cooled to 95° C. and 4 ml of heat stable .alpha.-amylase, which is commercially available from Sigma-Aldrich Corp., St. Louis, Mo., was added. The starch was hydrolyzed at about 90 to 95° C. for 30 min, and then the mixture was cooled in an ice bath to 50° C. The pH was adjusted to 6.0, and 5 ml of neutral protease, which is commercially available as Sigma P1236 protease from Bacillus amyloliquefaciens from Sigma-Aldrich Corp., St. Louis, Mo., were added. Protein was hydrolyzed at 50° C. for 4 hours, and then the mixture was brought to a boil to inactivate enzymes, cooled in an ice bath, and the pH adjusted to 7.0. The slurry was centrifuged at 10,000×g for 10 minutes. The residue was washed 3 times with water, dried in a forced draft oven at 40° C. for 48 hours, ground in a cyclone mill, and passed through a 0.8 mm screen to yield enzyme treated bran fiber. These steps produced a destarched proteolyzed enzyme modified bran.
The enzyme modified bran then underwent an alkaline-hydrogen peroxide method (23-24), with modifications. Fifty grams of the enzyme-treated bran from above were suspended in 1 L of 1 M sodium hydroxide. Under constant mixing at 60° C., 42 ml of 30% hydrogen peroxide was slowly added to the mixture, which was stirred for a total of 4 hours, and then centrifuged (10,000×g for 10 minutes), followed by the addition of 3 volumes of 95 ethanol to the supernatant. The mixture was held overnight at 4° C., and then the aqueous ethanol portion, containing the liberated ferulic acid, was siphoned off, discarded, and the precipitated material was washed with 80% ethanol, anhydrous ethanol, and acetone. The resulting powder was air dried until no solvent could be detected by odor, and then further dried in an oven at 40° C. for 24 hours. The resulting residue was an alkali-soluble polysaccharide fraction isolated from the bran.
The alkali-soluble bran fraction then underwent a graded ethanol precipitation process, which involves rehydrating 30 grams of the alkali-soluble bran with 3% w/w water. Then 95% ethanol was added in an amount to achieve a concentration of 40% ethanol to the water and alkali-soluble bran mixture under continuous stirring for 30 minutes and kept in a refrigerator at 4° C. overnight. The mixture was then centrifuged for thirty minutes at 6° C., which provided a precipitate that was insoluble in 40% ethanol and a supernatant. Ethanol 95% was added to the supernatant to obtain a concentration of 60% ethanol by volume under continuous stirring for 30 minutes and was refrigerated overnight. The 60% ethanol mixture was then centrifuged at 10000×g for thirty minutes at 6° C. to yield a supernatant, which was discarded, and a precipitate that was insoluble in 60% ethanol. The ethanol was removed from the precipitate by air drying. The precipitate was rehydrated in deionized water and dried in a freeze drier, and was termed “corn arabinoxylan” or “CAX”. In case of alkali-soluble bran from wheat and rice, 95% ethanol was added in an amount to achieve a concentration of 90% ethanol to the water and alkali-soluble bran mixture under continuous stirring for 30 minutes and kept in a refrigerator at 4° C. overnight. The mixture was then centrifuged for thirty minutes at 6° C., which provided a precipitate that was insoluble in 90% ethanol and a supernatant which was discarded. The ethanol was removed from the precipitate by air drying. The precipitate was rehydrated in deionized water and dried in a freeze drier.
A hydrolyzate of the CAX fraction was prepared by the following endoxylanase treatment. Twenty-five grams of the CAX fraction was suspended in 1,250 ml of 25 mM sodium acetate buffer having a pH of about 5.0. Then 12.5 ml of endoxylanase an enzyme commercially available as MULTIFECT™ CX XL having an activity of 445 XAU/ml from Genencor was added to the suspension, which was incubated in a shaking incubator at 55° C. for 26 hours. The enzyme suspension was then boiled for 30 minutes to inactivate the enzyme and centrifuged at 8000×g for thirty minutes. The small amount of precipitate was discarded to yield a hydrolyzate suspended in the supernatant. The supernatant was then dried in a freeze drier for 2 days at −60° C. to yield a hydrolyzate fraction.
After the endoxylanase treatment, the dried hydrolyzate fraction underwent a graded ethanol precipitation which involved rehydrating 10 grams of the hydrolyzate 3% w/w water. Then 95% ethanol was added in an amount to achieve a concentration of 40% ethanol to the water and hydrolyzate mixture under continuous stirring for 30 minutes and kept in a refrigerator at 4° C. overnight. The mixture was then centrifuged for thirty minutes at 6° C., which provided a precipitate that was insoluble in 40% ethanol and a supernatant. The precipitate was discarded. Ethanol 95% was added to the supernatant to obtain a concentration of 60% ethanol by volume under continuous stirring for 30 minutes and was refrigerated overnight. The 60% ethanol mixture was then centrifuged at 10,000×g for thirty minutes at 6° C. to yield a supernatant and a precipitate, referred to as “grain 40-60%” and “hydrolyzate.” The supernatant was suspended in a concentration of ethanol up to 90% by volume by repeating the steps above to yield a fraction that is a precipitate insoluble in 90% ethanol by volume, referred to as “grain H 60-90%” and hydrolyzate. The corn hydrolyzate was referred to as “CH 40-60%” because it was precipitated between ethanol concentrations of 40% and 60%; the wheat hydrolyzate was referred to as “WH 40-60%” because it was precipitated between ethanol concentrations of 40% and 60%; and the rice hydrolyzate was referred to as “RH 60-90%” because it was precipitated with modified method between ethanol concentrations of 60% and 90%.
The CAX and hydrolyzate products of the corn bran were then tested, however, only the hydrolyzate product (not the CAX product) of wheat and rice bran were tested. Note that the tested samples are labelled CAX and hydrolyzate through the data and results section of this example. “CAX” in the testing and results section of this example is referring to the final CAX product after the graded ethanol precipitation and drying. The final hydrolyzate product after the graded ethanol precipitation and drying is referred to as the final corn hydrolyzate product as “CH 40-60%”, the final wheat hydrolyzate product was referred to as “WH 40-60%,” and the final rice hydrolyzate product was referred to as “RH 60-90%.”
In vitro digestion and fermentation involved the same methods as used in Example 1 except that phenol sulfuric method was used to determine the total carbohydrate in these samples. The fermentation analysis involved the same steps and procedures as in Example 1.
The viscosity of the CAX and hydrolyzate of the corn bran was tested using concentrations of 5% and 10% by volume of CAX or hydrolyzate in deionized water. The 5% or 10% mixture was boiled for 2 minutes and allowed to cool to room temperature. The viscosity was measured using a rotational rheometer, which is commercially available as AR-G2 from TA Instruments, Newcastle, Del. A 20 mm diameter parallel plate geometry was used with 500 gap. Shear rate was varied from 0.01 to 150 (Vs).
The data analysis used SAS software (version 9.2, SAS institute, Cary, N.C.) to calculate statistical differences, which were defined as P<0.05.
The sample composition prior to in vitro digestion is shown in Table 4 as follows:
The SCFA and BCFA produced during in vitro fermentation are provided below in Table 5:
The total SCFA and BCFA after 24 hours are shown above in Table 5, the CAX and hydrolyzate end products produced by the methods described above show an increase in SCFAs as compared to untreated corn, wheat, and rice brans, see Table 3. The BCFAs rose in all treated samples, which indicates proteolysis.
The gas production from in vitro fermentation of the tested samples is provided in Table 6 below:
As shown in Table 6 and compared to
The 5 and 10% CAX and CH 40-60% were observed for visual characteristics. The CH 40-60% hydrolyzate was lighter in color at both concentrations as compared to the CAX, which provides greater versatility for the use of CH 40-60% in a beverages or other liquids.
A further study was done on a more defined collection of arabinoxylans in order to draw more detailed relationships between structural aspects of the fiber polymers and their fermentation rate and short chain fatty acid composition. These alkali-extracted soluble arabinoxylans were chosen to provide a wide range of initial fermentation rates, and sources with certain linkage patterns were found to drive slow fermentation. Procedures to obtain these fiber samples are described at the end of this section. Unusual as well as complex linkages within wheat arabinoxylan hydrolyzate (WH), corn arabinoxylan (CAX), and corn arabinoxylan hydrolyzate (CH) polymers presumably are digested, and released sugars fermented, by relatively few bacteria compared to more common and simple compositions and linkages found particularly in sorghum arabinoxylan (SAX) and also rice arabinoxylan hydrolyzate (RH) polymers, and may explain their comparably slow initial fermentation rate. This identification of structural patterns for slow fermentation provide a path forward to produce more soluble fibers that are tolerable by fermenting slowly and into the distal colon.
The fermentation patterns of the arabinoxylans were classified into 2 groups based on their rate of fermentation: WH, CAX and CH as slow fermenting substrates, and SAX and RH as rapid fermenting substrates (
Total SCFAs generally mirrored gas fermentation profiles with RH having higher overall higher levels at 8 and 12 h (
Although fermentation of the arabinoxylans generated lower amounts of butyrate than that of FOS, which is considered butyrogenic there were notable differences in levels produced (
Linkage results of the tested arabinoxylans are given in Table 7. Assuming that (1,4)-linked, (1,3,4)-linked and (1,2,3,4)-linked xylose residues belonged only to the xylan backbone, percentage of unsubstituted, mono-substituted and di-substituted xylose units of all alkali-soluble arabinoxylans were calculated. Percent of unsubstituted xylose residues ranged from 0-36%, showing a high degree of substitution in all of the arabinoxylans tested. The amount of unsubstituted xylose was 24% in CAX, 30% in SAX, and 37% for RH. Unlike the other arabinoxylans studied, WH had 0% unsubstituted xylose as indicated by the absence of a peak at the retention time 17.356-17.361 min assigned to 2,3-di-O-methylxylose (unsubstituted xylose units). Additionally, partially methylated alditol acetates of WH revealed a peak at the retention time 17.402 min showing 5-O-methylarabinose (or 2,3-branched arabinose residues). This unique linked-arabinose was confirmed by the appearance of many signals in the regions of α-
The lowest rate of fermentation was found in WH, followed by CH and CAX. Only WH contained the second level sugars linked at O-2,3 of the xylan backbone-linked arabinose residue. Therefore, the two combinations of single xylose branched chain and oligosaccharide side chain with two sugars linked at O-2,3 of arabinose residues resulted in the lowest rate of fermentation. The fermentation rates of CH and CAX were much slower than those of SAX and RH and they contained only single xylose branched chains. Therefore, the single xylose branched chain may be the key feature of slow fermentation rate. CAX and CH additionally had comparably high amounts of arabinose linked at the O-2, 3, and 5 positions (of total arabinose).
The proportion of terminal arabinose was relatively high in WH (32 mol %), SAX (39 mol %) and RH (26 mol %), while considerable amount of terminal xylose was found in CAX (23 mol %), CH (23 mol %) and WH (24 mol %) (Table 8). Terminal xylose is either the one xylose residue of the xylan backbone at the non-reducing end, a branch chain linked to C-3 position of certain xylose residues or linked at O-2 or O-3 of arabinose units in branches. By subtracting the mol (%) of terminal xylose 2-linked and 3-linked to arabinose from the mol (%) of total terminal xylose, the mol (%) of terminal xylose left for direct linking to the xylan backbone was approximately 22% for CAX, 19% for CH, and 32% for WH (Table 8). RH and SAX had no terminal xylose directly linked to the RH and SAX xylan backbones.
Terminal xylose residues attached to the xylan backbone appears to be a key factor related to slow fermentation as a considerable amount of this linkage was found in the slow fermenting arabinoxylans, CAX, CH, and WH. CH, which was somewhat slower fermenting initially than CAX, contained a higher mol (%) of 2-linked, 3-linked, and 5-linked arabinose residues, but a lower proportion of terminal arabinose. Apart from branches with single xylose units, oligosaccharide side chains with the second sugar linked at O-2, O-3, and O-5 of the xylan backbone-linked arabinose residues could also be an important factor of slow fermentation. Oligosaccharide side chains with a second sugar linked at O-2,3 of the xylan backbone-linked arabinose residues was found only in WH, which could be another key factor of its slow fermentation profile. On the other hand, SAX (a fast fermenting substrate) contained a much higher proportion of terminal arabinose single branch chains that were easily and rapidly hydrolyzed.
Accordingly, the invention is directed to a composition suitable for oral mammalian administration comprising a treated bran product consisting essentially of dry-milled, partially-defatted, amylase-treated and protease-treated, alkali-soluble, ethanol-precipitated bran, wherein the treated bran product may comprise a high proportion of single β-
Ara in the side chain may comprise about 20% of total Ara residues, compared to other sources which lacked this side chain, and/or the bran product may contain comparably high amounts (about 20%) disaccharide side chains of an α-
The inventors have discovered that such a treated bran product ferments in the distal colon of a mammal faster and to a greater degree than a grain product comprising rapidly fermenting soluble dietary fibers and that the treated bran product ferments throughout colon of a mammal at a slower rate than a grain product comprising rapidly fermenting soluble dietary fibers and that fermentation of the treated bran product in the colon of a mammal yields increased short chain fatty acid production compared to short chain fatty acid yield from fermentation of rapidly fermenting soluble dietary fibers in the colon of a mammal. Furthermore, fermentation of the treated bran product in the colon of a mammal yields decreased carbohydrate content compared to carbohydrate content from fermentation in the colon of a mammal of rapidly fermenting soluble dietary fibers. The inventors also have discovered that orally administering to a mammal about 0.1 grams to about 50 grams of the treated bran product, increases short chain fatty acid concentration in the colon of the mammal and thereby improves bowel health of the mammal.
To prepare alkali-extractable arabinoxylan, fat was removed from the bran (300 g) by mixing with hexane twice [bran:hexane, 1:7 (w/v)] at room temperature for 60 min each. Starch and protein removal was performed using enzymatic treatment (65). Defatted bran (150 g) was suspended in 1000 ml of deionized water and pH was adjusted to 7.0. The mixture was boiled under continuous stirring for 5 min and then cooled to 95° C. Heat-stable α-amylase (6 ml) was added and the mixture was incubated at 90-95° C. for 60 min, and then cooled down to 50° C. in an ice bath. The pH was adjusted to 6.0 with 1 N HCl and the suspension was incubated with protease (7.5 ml) under continuous agitation at 50° C. overnight, and then boiled for 10 min to inactivate enzymes. After cooling down, the slurry was centrifuged at 10,000 g for 10 min. The bran residue was washed 4 times with deionized water, air dried, and ground. For alkaline-hydrogen peroxide extraction (66), destarched and proteolyzed bran (100 g) was suspended in 1000 ml of 1 N NaOH, and stirred continuously at 60° C. for 4 h. During the first 2 h of mixing, 15 ml of 30% hydrogen peroxide was added slowly to increase the efficiency of the delignification and to prevent excessive foaming. The mixture was cooled down and centrifuged at 10,000 g for 10 min. The residue was washed once with 1 N NaOH and then centrifuged. Both supernatants were combined, neutralized with 6 N HCl. 4 volumes of 95% ethanol were added with continuous stirring, mixed for 30 min, and stored overnight at 4° C. The slurry was filtered using a vacuum flask fitted with a glass filter funnel. The residue was air-dried and named an alkali-soluble fraction. Alkali-soluble fractions obtained from wheat, rice, and sorghum brans were named “WAX”, “RAX”, and “SAX”, respectively. No graded ethanol fractionation was applied for these three substrates.
Fractionation of the alkali-soluble portion obtained from corn bran was performed (67). The alkali-soluble portion (60 g) was solubilized in of deionized water (1,940 g, 3.0% w/w). Ethanol (95%) was slowly added under continuous stirring at room temperature so as to make a final concentration of 40% ethanol. The mixture was stirred for 30 min at room temperature, stored overnight at 4° C. and centrifuged (10,000 g, 30 min, 6° C.). The precipitate was dried in a hot air oven, dissolved in deionized water, and then lyophilized. This obtained fraction was designated as CAX0-40%. Then the concentration of ethanol in the supernatant was brought up to 60% to precipitate the largest fraction of the corn arabinoxylans. After addition of ethanol, the steps described above were repeated and the collected precipitate was designated CAX40-60%. The yield of fraction CAX0-40% was fairly low, therefore only fraction CAX40-60% was used for further sample preparation and the term “CAX” was used instead of CAX40-60%.
Hydrolyzates of the alkali-soluble portions were prepared [21]. Alkali-soluble portions (CAX, WAX, and RAX) (25 g) were dissolved in 1,250 ml of sodium acetate buffer (25 mM, pH˜5.0) and then 12.5 ml of MULTIFECT® CX XL endoxylanase was added. The mixtures were incubated in a shaking incubator at 55° C. for 26 h, boiled for 30 min to inactive enzymes, and then centrifuged at 8,000 g for 30 min. The residues were discarded and the supernatant was lyophilized yielding CAX or WAX or RAX hydrolyzates. The collected hydrolyzates (30 g) were solubilized in 970 g of deionized water (3.0% w/w) and fractionated in a manner similar to that of the alkali-soluble portion. Hydrolyzates0-40% from CAX, WAX, and RAX were named CH0-40%, WH0-4%, and RH0-40%. Similar assigned names were used for fractions 40-60% and 60-90%. After the determination of molecular size and ratio of arabinose to xylose (A/X ratio), CH40-60% was classified in the low Mw and low A/X ratio group, whereas, RH60-90% was in the low Mw but high A/X ratio group. WH40-60% on the other hand, had both high Mw and A/X ratio value. Therefore, only CH40-60%, WH40-60% and RH60-90% were selected, due to their range of structural features, for further analysis and named CH, WH and RH, respectively.
The foregoing description and embodiments are intended to illustrate the invention without limiting it. It will be obvious to those skilled in the art that the invention described herein can be essentially duplicated by making minor changes in the material content or the method of manufacture. To the extent that such material or methods are substantially equivalent, it is intended that they be encompassed by the following claims.
This patent application is a continuation-in-part of U.S. patent application Ser. No. 12/791,802, filed Jun. 1, 2010, which claims benefit to U.S. Provisional Patent Application No. 61/182,381, filed on May 29, 2009, each of which is incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61182381 | May 2009 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12791802 | Jun 2010 | US |
| Child | 14491203 | US |
