Patent Application
20230174924
The present invention, in some embodiments thereof, relates to a method of culturing Bacilli bacteria and use of the culture for generating food products and pigments.
Many bacterial species exist in natural settings as matrix-enclosed multicellular cells called biofilm. Bacillus subtilis is a beneficial Gram-positive, spore-forming bacterium ubiquitously found in soil, gastrointestinal tract (GIT) of ruminants/humans and also in food processing plants. B. subtilis inclines to form diverse biofilm phenotypes including pellicle or biofilm bundles in liquid media, and colony-type biofilm in solid media. Environmental and physiological conditions often dictate the B. subtilis cells for instigating the biofilm mode of growth.
Bacillus species belong to a versatile class of microbes that may provide numerous health benefits for the host organism. Some of those species are known to antagonize bacterial pathogens, while others protect or/and promote the growth of probiotic bacteria. In addition, Bacillus-based probiotics have shown to improve the digestive health by strengthening the intestinal barrier function and by attenuation of the inflammatory response in humans.
Probiotic Bacillus species have also a propensity to colonize human gut transiently. However, the prospect of probiotic survival in the acidic environment of human GIT is either infrequent or virtually nil. Several studies have been conducted previously to enhance a survival of probiotic species in GIT using food matrices [11-13].
Plant-based milks are gradually gaining attention due to their copious nutritional values. It is usually prepared by crushing legumes or nuts with 6 to 8 volumes of water. Lately, there is substantial interest in preparing chickpea (Cicer arietinum) based milks. Chickpea seeds are rich in healthy nutrients, minerals, proteins, carbohydrates and dietary fibers. It also has traditional standards and is a popular cuisine in India, middle-east and Mediterranean.
According to an aspect of the present invention there is provided a method of culturing bacteria of the Bacilli class, the method comprising:
According to an aspect of the present invention there is provided a method of generating a pigment comprising:
(a) culturing bacteria belonging to the genus Bacillus on a medium comprising pasteurized starch fibers of a legume of a leguminous plant under conditions that allow the secretion of the pigment into the medium; and
(b) collecting the medium.
According to an aspect of the present invention there is provided a culture comprising bacteria belonging to the class Bacilli and a medium comprising starch fibers of a pasteurized legume of a leguminous plant.
According to an aspect of the present invention there is provided a method of coloring a food product comprising combining a pigment generated by Bacillus subtilis with the food product under conditions that alter the color of the food product, thereby coloring the food product.
According to an aspect of the present invention there is provided a food product comprising a pigment generated by Bacillus subtilis, wherein the food is of a different color in the presence of the pigment as compared to in the absence of the pigment.
According to an aspect of the present invention there is provided a food product comprising the culture described herein.
According to an aspect of the present invention there is provided a culture medium comprising chickpea milk fortified with exogenous chickpea starch fibers.
According to embodiments of the invention, the medium is chickpea milk.
According to embodiments of the invention, the chickpea milk is fortified with exogenous chickpea fibers.
According to embodiments of the invention, the medium is a growth medium selected from the group consisting of lysogeny broth (LB), lysogeny broth enriched with glycerol and manganese (LBGM), milk and Man, Rogosa and Sharpe (MRS) medium.
According to embodiments of the present invention, the bacteria belong to the genus Bacillus.
According to embodiments of the present invention, the bacteria are comprised in a biofilm on the starch fibers.
According to embodiments of the present invention, the leguminous plant is selected from the group consisting of a plant of the genus Glycine, a plant of the genus Phaseolus, a plant of the genus Cicer, a plant of the genus Pisum, a plant of the genus Lens, a plant of the genus Cajanus, a plant of the genus Vicia, and a plant of the genus Arachis.
According to embodiments of the present invention, the leguminous plant selected from the group consisting of chickpea (Cicer arietinum), soybean (Glycine max), common bean (Phaseolus vulgaris), pea (Pisum sativum), lentil (Lens culinaris), pigeon pea (Cajanus cajan), broad bean (Vicia faba) and peanut (Arachis hypogaea).
According to embodiments of the present invention, the leguminous plant is chickpea.
According to embodiments of the present invention, the bacteria is of a species selected from the group consisting of Bacillus subtilis, Bacillus sonorensis, Bacillus licheniformis, Bacilllus firmus, Bacillus megaterium, B. endophyticus, Bacillus endophyticus and Bacillus amyloliquefaciens.
According to embodiments of the present invention, the bacteria are of the species Bacillus subtilis.
According to embodiments of the present invention, the method further comprises purifying the pigment following step (b).
According to embodiments of the present invention, the pigment is comprised in a culture of starch fibers of a legume of a leguminous plant.
According to embodiments of the present invention, the food product is a meat.
According to embodiments of the present invention, the pigment is devoid of material of the leguminous plant.
According to embodiments of the present invention, the food product further comprises a legume of a leguminous plant.
According to embodiments of the present invention, the food product is essentially devoid of material of a legume of a leguminous plant.
According to embodiments of the present invention, the food product is a dry snack.
Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.
The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced.
In the drawings:
The present invention, in some embodiments thereof, relates to a method of culturing Bacilli bacteria and use of the culture for generating food products and pigments.
Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details set forth in the following description or exemplified by the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways.
Bacilli exist in natural settings as matrix-enclosed multicellular cells called biofilm. Whilst analyzing the properties of a biofilm of a particular Bacilli species cultured on chickpea starch fibers, the present inventors noticed intriguing morphological changes enabling extraordinary adaptability of the bacterial cells to growth upon the fibers (
Thus, according to a first aspect of the present invention, there is provided a method of culturing bacteria of the Bacilli class, the method comprising:
(a) adding the bacteria to a medium comprising pasteurized starch fibers of a legume, and
(b) culturing the bacteria under conditions that promote generation of a biofilm of the bacteria on the starch fibers, thereby culturing the bacteria.
Bacteria belonging to the class Bacilli, includes the orders Bacillales and Lactobacillales. In one embodiment, the bacteria are of the genus Bacillus, e.g. of the species Bacillus subtilis, Bacillus sonorensis, Bacillus licheniformis, Bacillius firmus, Bacillus megaterium, B. endophyticus, Bacillus endophyticus and Bacillus amyloliquefaciens.
According to a particular embodiment, the species is Bacillus subtilis.
Exemplary strains of Bacillus species contemplated by the present invention include, but are not limited to B. paralicheniformis MS303, B.licheniformis MS310, B. paralicheniformis S127, B. subtilis MS1577, NCIB3610, B. subtilis natto, B. subtilis 168 and B. subtilis PY79.
The term “legume” refers to the seeds or fruit of a leguminous plant.
Examples of leguminous plants which comprise starch fibers on which the bacteria may be cultured include plants of the genus Glycine, plants of the genus Phaseolus, plants of the genus Cicer, plants of the genus Pisum, plants of the genus Lens, plants of the genus Cajanus, plants of the genus Vicia, plants of the genus Arachis, plants of the genus Medicago, plants of the genus Neptunia, plants of the genus Trigonella, and plants of the genus Psophocarpus. Preferred examples thereof include plants of the genus Glycine, plants of the genus Phaseolus, plants of the genus Cicer, plants of the genus Pisum, plants of the genus Lens, plants of the genus Cajanus, plants of the genus Vicia, and plants of the genus Arachis. More preferred examples thereof include plants of the genus Glycine, plants of the genus Phaseolus, plants of the genus Cicer, and plants of the genus Pisum. Further preferred examples thereof include plants of the genus Glycine.
Examples of the plant of the genus Glycine include soybean (Glycine max). Examples of the plant of the genus Phaseolus include common bean (Phaseolus vulgaris). Examples of the plant of the genus Cicer include chickpea (Cicer arietinum). Examples of the plant of the genus Pisum include pea (pea sprout) (Pisum sativum). Examples of the plant of the genus Lens include lentil (Lens culinaris). Examples of the plant of the genus Cajanus include pigeon pea (Cajanus cajan). Examples of the plant of the genus Vicia include broad bean (Vicia faba). Examples of the plant of the genus Arachis include peanut (Arachis hypogaea). Examples of the plant of the genus Medicago include alfalfa (Medicago sativa). Examples of the plant of the genus Neptunia include water mimosa (Neptunia oleracea). Examples of the plant of the genus Trigonella include fenugreek (Trigonella foenum-graecum). Examples of the plant of the genus Psophocarpus include
Goa bean (Psophocarpus tetragonolobus).
In a particular embodiment, the legume is chickpea.
As used herein, the phrase “starch fiber” refers to a polysaccharide comprising at least 3 sugar monomers. The size of fibers may vary between 10-1000 μm.
Starch fibers typically auto-fluoresce when visualized under a confocal laser scanning microscope. Propidium iodide (PI) staining may be used to confirm the presence of starch fibers since it selectively stains the auto-fluorescent starch particles and does not penetrate the membranes of starch granules.
Methods of releasing (or enhancing the amount of) starch fibers from legumes include heating (e.g. cooking) for an amount of time such that autofluorescence may be observed under a fluorescent microscope. Thus, for example chickpeas may be cooked for about 20 minutes to about 60 minutes.
The starch fibers may be retrieved from fresh legumes, frozen legumes, dried legumes or canned legumes.
The legumes may be treated prior to heating to enhance the process of starch fiber release. Thus, the legume may be soaked, crushed, milled and/or homogenized prior to heating.
Optionally, the heated legumes may be further treated prior to use. Exemplary treatment methods include filtration, homogenization and extraction.
Once the starch fibers are released from the legume, they may be used as part of a culture medium. The culture medium is pasteurized or sterilized.
In one embodiment, the culture medium is a chickpea milk i.e. a liquid chickpea suspension, as further described in the methods section herein below, which comprises chickpea starch fibers.
In another embodiment, the culture medium is a medium known for culturing bacillus, to which isolated (exogenous) chickpea fibers have been added. Additional methods of isolating chick pea fibers are known in the art—see for example US Patent Application No. 20200390131, the contents of which are incorporated herein by reference.
In one embodiment, chickpea fibers are isolated using the following steps:
Thus, the present invention contemplates growth media which are fortified with chickpea fibers (e.g. dried chickpea fibers). In one embodiment, the growth medium is chickpea milk fortified with exogenous (i.e. isolated) chickpea starch fibers.
The term “pasteurization” as used herein refers to a heating process that results in the reduction of the number of viable pathogens in the culture medium so they are unlikely to cause disease when consumed by a human (assuming the pasteurized product is stored as indicated). In one embodiment, the pasteurization does not affect the taste or texture of the product.
As used herein, the term “sterilization” refers to a process that eliminates or removes all forms of fungi, bacteria, viruses, spore forms, or other microbiological organisms present in the culture media, or other suitable items.
Prior to addition of the bacteria to the culture medium, the pH may be adjusted.
In one embodiment, the pH of the culture medium is higher than 6.
The bacteria, which is added to the culture medium, may be in a starter culture, as known in the art.
Culturing of the bacteria in the culture medium is carried out under conditions that promote the generation of biofilm on the starch fibers present in the medium.
In one embodiment, the culture medium is a liquid medium.
In another embodiment, the culture medium is a solid medium (e.g. further comprises a gelling agent).
Examples of gelling agents contemplated by the present invention include, but are not limited to agar, guar gum, xanthan gum, locust bean gum, gellan gum, polyvinyl alcohol, alkylcellulose, carboxyalkylcellulose and hydroxyalkylcellulose.
As mentioned, the culture conditions are such that they allow for generation of a biofilm on the fibers.
The present inventors have uncovered particular components of a culture medium that are important for biofilm generation of bacteria being of the genus Bacillus (e.g. of the species B. subtilis). Thus, the present inventors propose that the medium used for culturing the B. subtilis further comprises manganese. In another embodiment, the medium further comprises glycerol. In still another embodiment, the medium further comprises dextrose. In still another embodiment, the medium used for culturing comprises both manganese and dextrose.
Other conditions of the culture that may be altered to enhance generation of a biofilm include, but are not limited to environmental parameters such as pH, nutrient concentration, co-culture of additional bacteria and temperature.
In one embodiment, the culturing is carried out in a bioreactor.
As used herein, the term “bioreactor” refers to an apparatus adapted to support the growth of bacteria on the starch fibers.
The bioreactor will generally comprise one or more supports for the starch fibers, and wherein the support is adapted to provide a significant surface area to enhance the formation of biofilm over the starch fibers. The bioreactors of the invention may be adapted for continuous throughput.
It will be appreciated that when the biofilm is generated in a bioreactor system, the conditions of the culture can be altered by altering the microfluidics (e.g. sheer stress) of the system.
As mentioned, agents or conditions are selected that bring about an advantageous change in a property of the biofilm. In one embodiment, the property is the amount of biofilm. In one embodiment, the property is the thickness of biofilm. In another embodiment, the property is the density of the biofilm. In yet another embodiment, the property is the rate in which the biofilm is formed. In still another embodiment, the property is the amount of additional bacteria which is incorporated into the biofilm. In still another embodiment, the property is the resistance to temperature and/or pH. In still another embodiment, the property is the amount of pigment generated (or secreted) by the bacteria, as further described herein below.
The culturing of this aspect of the present invention may be carried out in the presence of additional agents that serve to increase propagation of the B. subtilis bacteria and/or enhance biofilm formation. Such agents include for example acetoin.
The amount of acetoin and the timing of addition may be altered so as to promote optimal biofilm production. In one embodiment, about 0.01-5% acetoin is used. In another embodiment, about 0.01-4% acetoin is used. In another embodiment, about 0.01-3% acetoin is used. In another embodiment, about 0.01-2% acetoin is used. In another embodiment, about 0.01-1% acetoin is used. In another embodiment, about 0.01-0.5% acetoin is used.
In one embodiment, about 0.05-5% acetoin is used. In another embodiment, about 0.05-4% acetoin is used. In another embodiment, about 0.05-3% acetoin is used. In another embodiment, about 0.05-2% acetoin is used. In another embodiment, about 0.05-1% acetoin is used. In another embodiment, about 0.05-0.5% acetoin is used.
In one embodiment, about 0.1-5% acetoin is used. In another embodiment, about 0.1-4% acetoin is used. In another embodiment, about 0.1-3% acetoin is used. In another embodiment, about 0.1-2% acetoin is used. In another embodiment, about 0.1-1% acetoin is used. In another embodiment, about 0.1-0.5% acetoin is used.
The cultures of this aspect of the present invention are propagated for a length of time sufficient to generate a biofilm on the starch fibers which incorporates the Bacillus bacteria.
In one embodiment, the conditions are selected such that the amount of biofilm produced by the Bacillus is enhanced and the amount of a pigment secreted from the biofilm is enhanced. Alternatively, the conditions are selected such that the amount of pigment secreted by the Bacillus is enhanced.
According to a particular embodiment, the color of the pigment is dark brown/red.
Preferably, the Bacillus bacteria are cultured for at least 6 hours, 12 hours, 24 hours, 48 hours, 3 days, 4 days, 5 days, 6 days, 7 days, 8 days, 2 weeks, 3 weeks or longer to allow for sufficient quantities of a pigment to be generated and/or for sufficient quantities of biofilm to be generated.
In one embodiment, the Bacillus bacteria are cultured at a temperature between 20-40° C., more preferably between 23-32° C.—for example at about 30° C.
As mentioned, the Bacillus bacteria generate a reddish brown pigment when cultured on starch fibers of legumes.
Thus, according to another aspect of the present invention there is provided a method of generating a pigment comprising:
(a) culturing bacteria belonging to the genus Bacillus on a medium comprising pasteurized starch fibers of a legume of a leguminous plant under conditions that allow the secretion of the pigment into the medium; and
(b) collecting the medium.
Conditions that allow for the secretion of pigment into the medium are typically those that promote formation of a biofilm, as described herein above.
Following sufficient time in culture, the pigment may be isolated from the culture.
Preferably, the method for isolating the pigment involves a step of removing the culture medium from the Bacillus cells. This extracellular fraction of the liquid fermentation medium is also termed the supernatant and this fraction can be separated from the Bacillus cellular fraction by e.g. centrifugation or filtration, or indeed by any other means available for obtaining a liquid fraction essentially without any bacterial cells present therein.
In particular embodiments of the invention, the purification comprises at least one size fractionation step. Preferably, this size fractionation step is performed on the extracellular fraction. This size fractionation step may ensure that every component of the composition has a molecular weight of at least a given value. The size fractionation step may be any size fraction known to the skilled person, for example ultracentrifugation, ultrafiltration, microfiltration or gel-filtration. Thus in a particular embodiment of the invention, the pigment is purified from a liquid growth medium by a method involving one or more purification steps selected from the group consisting of ultracentrifugation, ultrafiltration, microfiltration and gel-filtration. Preferably, the purification step(s) are selected from the group consisting of ultrafiltration, microfiltration and ultracentrifugation, even more preferably from the group consisting of ultrafiltration and microfiltration.
Ultrafiltration is a membrane process where the membrane fractionates components of a liquid according to size. The membrane configuration is normally cross-flow wherein the liquid containing the relevant components are flowing across the membrane. Some of the liquid, containing components smaller than the nominal pore size of the membrane will permeate through the membrane. Molecules larger than the nominal pore size will be retained. The desired product may be in the retentate or the filtrate. If the ultrafiltration is performed in order to prepare a composition, wherein every agent within the composition has a molecular weight above a given value, the desired product is in the retentate. If a serial fractionation is made, the product may be in the retentate or filtrate.
Microfiltration is a membrane separation process similar to UF but with even larger membrane pore size allowing larger particles to pass through.
Gel filtration is a chromatographic technique in which particles are separated according to size. The filtration medium will typically be small gel beads which will take up the molecules that can pass through the bead pores. Larger molecules will pass through the column without being taken up by the beads.
Gel-filtration, ultrafiltration or microfiltration may for example be performed as described in R Hatti-Kaul and B Mattiasson (2001), Downstream Processing in Biotechnology, in Basic Biotechnology, eds C Ratledge and B Kristiansen, Cambridge University Press) pp 189.
In another embodiment the pigment in the medium may be isolated by precipitation, such as precipitation with alcohol, such as ethanol and/or chromatographic methods. This may for example be performed essentially as described in WO2003/020944. It is also contemplated within the invention that the pigment is isolated by sequentially performing two or more of above-mentioned methods. By way of example the pigment may be isolated by first performing a size fractionation step followed by precipitation.
Other methods for isolating the pigment of this aspect of the present invention are also contemplated by the present inventors including but not limited to HPLC.
The pigment which is generated by the Bacillus bacteria may be used to color a food product.
Thus, according to another aspect of the present invention, there is provided a method of coloring a food product comprising combining a pigment generated by Bacillus subtilis with the food product under conditions that alter the color of the food product, thereby coloring the food product.
In one embodiment, the pigment is added in sufficient quantities such that it provided a red/brown color to a food product. The food product may comprise an animal derived meat protein or a plant-based protein that is used as a meat substitute.
In one embodiment, the pigment is added to a plant-based meat substitute in sufficient quantities such that it obtains a color of a raw, uncooked meat. In another embodiment, the pigment is added to a plant-based meat substitute such that it obtains the color of a cooked meat.
The food product typically comprises vegetable proteins or animal derived proteins. Animal derived protein materials that may be utilized include, but are not limited to, collagen protein, casein or caseinate proteins, and whey protein albumin. Vegetable protein materials which may be utilized include, but are not limited to, gluten materials and soy protein materials. Most preferably the protein in the protein containing material is a soy protein material such as soy protein isolate, soy protein concentrate, soy flour, soy flakes, or mixtures thereof, where the soy protein material preferably contains at least about 50% soy protein. These protein materials are commercially available from various manufacturers, for example, soy protein isolates that may be used in the invention include SUPRO 500E, SUPRO EX 31-33, and SUPRO 515-516, which can be purchased from Protein Technologies International, Inc., Checkerboard Square, St. Louis, Mo. 63164.
The protein containing material may also include adjuncts, including, but not limited to, starches, gums, and fibres, and mixtures thereof. The adjuncts may be included to impart various functionalities to the protein containing material to improve the meat-like characteristics of the protein containing material. For example, starch may be included in the protein containing material to increase the viscosity and gel forming capability of the protein containing material when the protein containing material is hydrated. Gums may be included in the protein containing material to enhance the flowability of the protein containing material. Fibres may be included in the protein containing material to enhance the structure of the protein containing material when hydrated.
The pigment may be added to the protein containing material in an aqueous solution, where the pigment is diluted in water before being added to the protein containing material. In one embodiment, the pigment is diluted in a small quantity of water to form an aqueous solution of the pigment, which is then dispersed with the protein containing material in a quantity of water for hydrating the protein containing material. Alternatively, a dry pigment and a protein containing material may be dispersed together in water for hydrating the protein containing material.
Preferably the colored hydrated protein containing material contains from about 0.0005% to about 0.005%, by weight, of the pigment.
Simultaneously in conjunction with hydration and treatment with the pigment, or after being hydrated and treated with the pigment, the protein containing material may be texturised by any of a number of known methods for texturising protein materials to provide a meat-like texture to the protein containing material. For example, known processes for texturising protein materials include creating bundles of spun fibres of protein material after hydration of a protein material; extruding a hydrated protein material at a controlled pH, where the fat content of the protein material is minimised; and forming a textured granulated gel of a hydrated protein material.
The colored protein containing material, optionally texturised and flavoured, may be used as a meat analogue or a meat extender (i.e. increases the volume/amount of an animal-based product). In one aspect of the invention, the colored protein containing material may be formed into patties or stuffed into casings by itself to form a meat analogue patty or sausage. The meat analogue patties and sausages may be cooked, for example by frying or broiling, at temperatures, and for a time period, effective to cook the meat analogue, for example from about 50° C. to about 260° C.
According to a particular embodiment, the pigment is added after it has been isolated from the bacterial culture.
In another embodiment, the pigment is added together with the bacterial culture described herein (i.e. together with the starch fibers of a legume, e.g. chickpea). This is advantageous in two respects—the bacteria of the bacterial culture may be probiotic (e.g. B. subtilis) and the starch fibers of the legume add nutritional value to the food product.
According to another aspect of the present invention, there is provided a food product comprising a culture which comprises bacteria belonging to the class Bacilli and a medium comprising starch fibers of a pasteurized legume of a leguminous plant.
The proportion of Bacilli bacteria to starch fibers of a legume may be such that the starch fibers serve to protect the probiotic Bacilli bacteria in the acid environment of the gastrointestinal tract of a person. Thus the proportion of Bacilli bacteria to starch fibers of the legume may be such that the starch fibers enhance survival of the probiotic Bacilli bacteria in an acid environment.
Examples of food products to which the culture may be added include breakfast cereals, dry snacks, pasta, cakes, chips, meat analogues.
As used herein the term “about” refers to ±10%.
The terms “comprises”, “comprising”, “includes”, “including”, “having” and their conjugates mean “including but not limited to”.
The term “consisting of” means “including and limited to”.
The term “consisting essentially of” means that the composition, method or structure may include additional ingredients, steps and/or parts, but only if the additional ingredients, steps and/or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure.
As used herein, the singular form “a”, “an” and “the” include plural references unless the context clearly dictates otherwise. For example, the term “a compound” or “at least one compound” may include a plurality of compounds, including mixtures thereof.
Throughout this application, various embodiments of this invention may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.
Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases “ranging/ranges between” a first indicate number and a second indicate number and “ranging/ranges from” a first indicate number “to” a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals therebetween.
As used herein the term “method” refers to manners, means, techniques and procedures for accomplishing a given task including, but not limited to, those manners, means, techniques and procedures either known to, or readily developed from known manners, means, techniques and procedures by practitioners of the chemical, pharmacological, biological, biochemical and medical arts.
It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.
Various embodiments and aspects of the present invention as delineated hereinabove and as claimed in the claims section below find experimental support in the following examples.
Reference is now made to the following examples, which together with the above descriptions illustrate some embodiments of the invention in a non-limiting fashion.
Generally, the nomenclature used herein and the laboratory procedures utilized in the present invention include molecular, biochemical, microbiological and recombinant DNA techniques. Such techniques are thoroughly explained in the literature. See, for example, “Molecular Cloning: A laboratory Manual” Sambrook et al., (1989); “Current Protocols in Molecular Biology” Volumes I-III Ausubel, R. M., ed. (1994); Ausubel et al., “Current Protocols in Molecular Biology”, John Wiley and Sons, Baltimore, Md. (1989); Perbal, “A Practical Guide to Molecular Cloning”, John Wiley & Sons, New York (1988); Watson et al., “Recombinant DNA”, Scientific American Books, New York; Birren et al. (eds) “Genome Analysis: A Laboratory Manual Series”, Vols. 1-4, Cold Spring Harbor Laboratory Press, New York (1998); methodologies as set forth in U.S. Pat. Nos. 4,666,828; 4,683,202; 4,801,531; 5,192,659 and 5,272,057; “Cell Biology: A Laboratory Handbook”, Volumes I-III Cellis, J. E., ed. (1994); “Culture of Animal Cells—A Manual of Basic Technique” by Freshney, Wiley-Liss, N. Y. (1994), Third Edition; “Current Protocols in Immunology” Volumes I-III Coligan J. E., ed. (1994); Stites et al. (eds), “Basic and Clinical Immunology” (8th Edition), Appleton & Lange, Norwalk, Conn. (1994); Mishell and Shiigi (eds), “Selected Methods in Cellular Immunology”, W. H. Freeman and Co., New York (1980); available immunoassays are extensively described in the patent and scientific literature, see, for example, U.S. Pat. Nos. 3,791,932; 3,839,153; 3,850,752; 3,850,578; 3,853,987; 3,867,517; 3,879,262; 3,901,654; 3,935,074; 3,984,533; 3,996,345; 4,034,074; 4,098,876; 4,879,219; 5,011,771 and 5,281,521; “Oligonucleotide Synthesis” Gait, M. J., ed. (1984); “Nucleic Acid Hybridization” Hames, B. D., and Higgins S. J., eds. (1985); “Transcription and Translation” Hames, B. D., and Higgins S. J., eds. (1984); “Animal Cell Culture” Freshney, R. I., ed. (1986); “Immobilized Cells and Enzymes” IRL Press, (1986); “A Practical Guide to Molecular Cloning” Perbal, B., (1984) and “Methods in Enzymology” Vol. 1-317, Academic Press; “PCR Protocols: A Guide To Methods And Applications”, Academic Press, San Diego, Calif. (1990); Marshak et al., “Strategies for Protein Purification and Characterization—A Laboratory Course Manual” CSHL Press (1996); all of which are incorporated by reference as if fully set forth herein. Other general references are provided throughout this document. The procedures therein are believed to be well known in the art and are provided for the convenience of the reader. All the information contained therein is incorporated herein by reference.
Bacterial Strains and Culture Conditions
All B. subtilis strains were cultured in Lysogeny broth (LB) comprising 10 g of tryptone, 5 g of yeast extract, and 5 g of NaCl or on solid LB medium supplemented with 1.5% agar. For generating the starter cultures, initially, the strains were streaked on LB agar plates from the glycerol stocks maintained at −80° C. and incubated overnight at 37° C. A colony from the overnight LB agar plate was inoculated in fresh LB and grown at 37° C. for 5 hours with 150 rpm. The resultant culture was used as the starter culture for all the experiments.
Chickpea Milk Preparation
Approximately, 187.5 g of Kabuli-type chickpea (Cicer arietinum) seed were soaked in 1.2 L of distilled water (DW) and incubated for 12 h at room temperature. Following incubation, fresh DW was replaced and the seeds were crushed using a blender. The liquid chickpea seed suspension, chickpea milk (CPM) was boiled for 10 minutes, filtered using a sieve, following which the pH was adjusted with lemon juice (for pH: 4.8, 5.8 and 6.1) or 1 mM NaOH (for pH: 7). Finally, CPM was autoclaved and stored for further assays.
Macroscopic Assessment of Biofilms
Starter cultures of the required strains were prepared as previously described. For pellicle formation assays, 5 μl of the bacterial suspensions (5×105 CFU/mL) were pipetted into 4 mL of CPM in a 12 well polystyrene plates, while for colony-type biofilm assays, 3 μl of the bacterial suspensions were spotted on a CPM solid medium supplemented with 1.5% agar. All the plates were incubated at 30° C. for 72 hours and images were captured using either a regular camera or a Zeiss Stemi 2000-C microscope with an axiocam ERc 5s camera (Zeiss, Germany).
Microscopic Analysis
For visualization of CPM components, propidium iodide (Promega, USA) and Lugol's stain was used, while for visualization of B. subtilis interactions with the CPM fibers, fluorescently tagged B. subtilis YC161 strain, that constitutively expressed the green fluorescent protein (GFP) was used. The samples were processed and stained as previously described [4] and visualized under a confocal laser scanning microscope (CLSM) (Leica, Wetzler, Germany). Strains that did not express GFP were stained with SYTO™ 9 dye from the Filmtracer live/dead biofilm viability kit (Promega, USA) in conformity with the guidelines.
In Vitro Digestion System
The survivability of B. subtilis WT and ΔsinI mutants in an acidic environment was monitored by an in vitro digestion system [2]. Briefly, the starters were diluted 1:100 into LB or CPM and incubated at 30° C. with shaking at 25 rpm for 24 h, following which the samples were subjected to in vitro gastro-intestinal digestion procedures as previously described [2]. Following in vitro digestion, samples were sonicated for 2 min (10 s pulse on/off) at 4° C. with 40% amplitude, plated on LB agar plates and incubated overnight at 37° C. Following incubation, the colonies were enumerated by colony forming units (CFU) method.
Assessment of Bacterial Sensitivity to Heat Treatment
The sensitivity of B. subtilis WT and sinI mutants to heat was monitored by pasteurization. Starter cultures of the bacterial strains were prepared as previously described. The cultures were then diluted 1:100 in CPM and grown for 24 h at 30° C. with 25 rpm shaking. Following incubation, the samples were then heat treated in three separate batches or tubes (63° C. for 3 min, 63° C. for 30 min, and 80° C. for 20 min) in a water bath. Immediately after pasteurization, the samples were sonicated for 2 min (10 s pulse on/off) at 4° C. with 40% amplitude with an Ultrasonic processor (Sonics, VCX 130, Newtown, USA), diluted, plated and incubated overnight at 37° C. The number of surviving cells was enumerated by CFU method.
Statistical Analysis
All experiments were conducted in triplicate, and results are expressed as means±standard deviations. Statistical significance was determined by pair-wise testing using the Students' t-test, and was accepted for p values of *p<0.05, **p<0.01, and ***p<0.001.
Initial microscopic analysis of the CPM medium revealed the presence of insoluble components that was categorized as non-fluorescent (
In order to determine whether these starch fibers might serve as a natural scaffold for bacteria to grow as biofilms, the fluorescently tagged wild type B. subtilis strain (YC161 (P spank-gfp)), that constitutively expresses the green-fluorescent protein (GFP), were cultured in CPM. Interestingly, it was found that B. subtilis YC161 selectively colonize the autofluorescent starch fibers apparently through tight interactions (
Since B. subtilis biofilm is basically reliant on extracellular polymeric substance matrix, the growth of strains (ΔtasA, and ΔepsH) that harbored mutants in matrix operons was assessed. None of them adhered to the auto-fluorescent fibers nor formed biofilm bundles in CPM (
Moreover, it was further observed that the WT cells of B. subtilis produce an inquisitive reddish-pink pigmentation in CPM that was somewhat contemporaneous in the epsH, tasA and spo0A mutants as well (
Next, pulcherrimin was further purified and compared between WT and sinI mutants. The results showed no pigment production in ΔsinI mutants (
Next, the ability of the WT strain to grow in different pHs was analyzed. Alkaline pH enhanced the robustness in the pellicles while pigment was best at lower pH (
Milk and dairy-free milk products like CPM need to undergo thermal processing like pasteurization before packaging. Probiotics are sensitive to heat and do not endure this procedure [22]. Techniques like microencapsulation have been shown to improve the viability and are often recommended [9]. It was anticipated that the prebiotic fibers in CPM might shield bacteria from physical stresses such as heat treatment. Consequently, the WT cells showed remarkable survivability, while amount of the ΔsinI mutant cells were significantly reduced following exposure to heat treatment (
Enrichment of chickpea milk (CPM) with chickpea fiber (CPF) results in improved pellicle formation and secretion of pinkish pigmentation (
Induction of Biofilm Formation in Regular Laboratory Medium
Next, it was determined if CPF has the ability to trigger biofilm formation independently of CPM medium. Lysogeny broth (LB), a laboratory medium that does not support the formation of biofilm pellicles was selected. LB was enriched by different dietary fibers and biofilm formation observed following 48 hours growth of B. subtilis. This was to verify if different types of dietary fibers, such as soluble fibers (wheat fiber) and insoluble fibers (cellulose) were also able to trigger this phenotype. Soluble fibers did not induce biofilm formation in B. subtilis, whereas insoluble fibers triggered the formation of pellicles as shown in
Growth Rate of B. subtilis in Supplemented Medium
B. subtilis cells grown in the presence of different concentrations of the dietary fibers did not affect the cell growth. Cells grew well in all the different media, with CPF having slightly higher cell counts, as illustrated in
Survival of B. subtilis Cells During In Vitro Digestion
The survivability of B. subtilis grown in the presence of different fibers was compared under simulated gut conditions. The results shown in the
Confocal Microscopy
B. subtilis cells grown in CPF showed a general increase in bundling and cell fluorescence with increasing concentrations. This implies that CPF aids in bundling of cells. Increasing concentrations of CPF caused more closely packed cells with more fluorescence, as shown in
Scanning Electron Microscopy
The morphology of B. subtilis was shown to differ under different culturing conditions. In control (LB), cells were observed as separated clusters. In the presence of CPF, the bacterial cells showed significant induction in matrix-embedded bundling (
Regulation of Matrix Gene Expression in the Presence of Dietary Fibers
A beta-galactosidase assay (Oknin et al., 2015) was used to determine the expression of one of the major matrix operons tapA involved in biofilm formation in the presence of different dietary fibers.
As illustrated in
Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.
It is the intent of the applicant(s) that all publications, patents and patent applications referred to in this specification are to be incorporated in their entirety by reference into the specification, as if each individual publication, patent or patent application was specifically and individually noted when referenced that it is to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting. In addition, any priority document(s) of this application is/are hereby incorporated herein by reference in its/their entirety.
This application is a Continuation of PCT Patent Application No. PCT/IL2021/050880 having International filing date of Jul. 19, 2021, which claims the benefit of priority under 35 USC § 119(e) of U.S. Provisional Patent Application No. 63/053,651 filed on Jul. 19, 2020. The contents of the above applications are all incorporated by reference as if fully set forth herein in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63053651 | Jul 2020 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/IL21/50880 | Jul 2021 | US |
| Child | 18098184 | US |
