Patent Application
20240240022
The present invention relates to novel methods to manufacture composite materials comprising amyloid fibrils and a biodegradable polymer. The methods described herein prove to be environmentally friendly and allow the use of starting materials of low quality/purity. Specifically, amyloid fibrils may be obtained from food waste. The invention further provides for novel composite materials comprising specific amyloid fibrils and a biodegradable polymer, to articles comprising such composite materials and to the use of such composite materials. The composite materials described herein show unexpected beneficial properties, when compared to the individual constituents. These beneficial properties include improved mechanical properties (e.g. flexibility), improved biodegradation, improved antioxidant properties, and beneficial optical properties (e.g. high transparency in the visible spectrum, combined with UV-blocking properties).
Plastic is one of the most abundant man-made materials and, although its widespread use started only 70 years ago, an estimate of 8300 million metric tons (Mt) of plastic have been produced to date. Plastic production was drastically accelerated by the intensive utilization of single-use containers, and packaging is now plastic's largest market. Approximately 150 Mt of solid plastic, corresponding to half of the annual global production, is thrown away each year worldwide. Most polymers used to produce plastics are derived from fossil hydrocarbons, posing a threat to fossil fuel sources. Additionally, most common plastics are not biodegradable and, if not permanently destroyed by proper thermal treatment, accumulate in the natural environment or in landfills causing devastating effects to the planet's ecosystem. Up to 80% of the global plastic waste ends up contaminating the environment, plastic debris is so abundant in the environment that it can be used as a geological indicator of the Anthropocene era.
Although recycling is suggested as a possible solution to some of these problems, this process remains limited to less than 9% of global plastic waste since it is costly, time-consuming, cannot be applied to many polymeric materials. Further, the quality of the polymers obtained by recycling is low.
The replacement of plastics by bioplastics is also suggested as a possible solution to some of these problems. Bioplastics include biodegradable plastics and bio-based plastics.
Bio-based plastics are produced employing renewable resources (such as cellulose, starch, polylactide or polyhydroxy-alkanoates) instead of fossil fuels. For example, US2004/0249065 discloses a method for producing biodegradable plastic from natural materials containing polysaccharides with a basic aqueous solution. Although suitable, the physical properties of the materials obtained are considered insufficient for many applications.
Protein-based biodegradable plastic is attracting attention due to their broad availability, fast biodegradation rates, and their food-grade nature, resulting in films that can even be classified as edible. The major drawbacks of protein-based bioplastic derive from the intrinsic nature of native protein monomers, which are typically globular, hydrophilic, and water soluble. These properties result in difficulties using conventional manufacturing processes, they show poor mechanical and barrier properties and are sensitive to water and humidity.
Composite materials, comprising specific amyloid fibrils and polymers, as well as their manufacturing, are described in literature, but they all fundamentally differ from the present invention.
Pilkington et al. (Biotechnol. Prog., 2010, 26(1), 93-100) discuss amyloid fibrils as a nanoscaffold for enzyme immobilization. The document discloses composite films, comprising: (i) polyvinyl alcohol (PVA) and (ii) pre-denatured amyloid fibrils from bovine insulin cross-linked with glucose oxidase (GOD). The results presented in table 2 show that GOD retains its activity composites, due to cross-linking on amyloid fibrils. The results further show that composites without cross-linking GOD to are disadvantageous. Further, it is noted that Pilkington et al. disclose preparation of composites where amyloid fibrils are first obtained in water solution and then polymer is added. This protocol is considered disadvantageous for commercial manufacturing and differs from the inventive method described below. Rao et al. (Biotechnol. Prog., 2012, 28 (1), 248-256) discuss Amyloid Fibrils as Functionalizable Components of Nanocomposite Materials. The authors proof the principle that incorporation of amyloid fibrils into a polymeric material can impart useful changes to the mechanical and morphologal properties of the films but also acknowledge more work is required to optimze the properties of the composites. Specifically, the document discloses composite films comprising: 0.6 wt % pre-denatured amyloid fibrils from bovine insulin and PVA. Further, it is noted that Rao et al. disclose preparation of composites where amyloid fibrils are first obtained in water solution and then polymer is added. Again, this protocol is considered disadvantageous for commercial manufacturing and differs from the inventive method described below.
Byrne et al. (European Polymer Journal 47 (2010) 1279-1283) discuss the preparation of novel nanofilled polymer composites using PLA and protein fibers. The document discloses composite films comprising: 1-5 wt % predenatured amyloid fibrils from native hen egg white lysozyme and PLA.
In all these publications, the starting materials for obtaining composites are of high purity, making these methods unsuitable for commercial applications. Further, the thus obtained composites do not comply with the market expectations in view of mechanical and/or optical properties. Still further, it is noted that Byrne et al disclose preparation of composites where amyloid fibrils are first obtained in water solution and then polymer is added. Again, this protocol is considered disadvantageous for commercial manufacturing and differs from the inventive method described below.
Knowles et al (WO2010/041009) discuss composites comprising a matrix component and a stiffening component. As matrix component, silicone polymers are described, as stiffening agent, amyloid fibrils are mentioned. It is noted that the polymers mentioned in that document lack biodegradability. Further, it is noted that Knowles et al disclose preparation of composites by adding dry amyloids to a monomer solution followed by polymerizing the monomers into a polymer to thereby obtain a composite material. Also this protocol is considered disadvantageous for commercial manufacturing and differs from the inventive method described below.
Accordingly, there is a need to provide advanced materials addressing human needs and considering our environment. There is a further need to replace presently used plastics by more sustainable materials. It would be considered beneficial if these advanced materials are easily available and can be processed using known technology.
There is a further need for providing manufacturing methods for composite materials being environmentally friendly and fit for application on a commercial scale.
One or more of the above objectives are achieved by the composite material as defined in claim 1 and the manufacturing method as defined in claim 9. Further aspects of the invention are disclosed in the specification and independent claims, preferred embodiments are disclosed in the specification and the dependent claims.
The inventive composite materials (“bioplastics”) are optimal candidates to produce shaped articles, such as films. In particular, amyloid fibrils may be used as building blocks for engineering novel bioplastics with targeted characteristics tuned by blending different functional additives such as bio-polymers and additives to improve the performances of the resulting commercial products, such as films. Additionally, other important properties such as water stability, hydrophobicity and antioxidant activity can be tuned by additives, chemical treatment or coatings. These novel bioplastics are characterized by a wide range of properties that can be achieved and tuned to avoid non-biodegradable or toxic compounds. Moreover, these bioplastics show great potential for commercialization with economic viability thanks to the very low cost of the protein used, which are mainly obtained, for example, by waste products of the food industry. Further, the manufacturing of novel composite materials is considered cheap, scalable, and environmentally friendly and specifically suited for film formation. Ultimately, producing bioplastic using food wastes helps food industries for two main reasons: not only it improves their production in terms of sustainability, waste management and valorization, but it also directly improves their circular economy.
The present invention will be described in more detail below. It is understood that the various embodiments, preferences and ranges as provided/disclosed in this specification may be combined at will. Further, depending on the specific embodiment, selected definitions, embodiments, or ranges may not apply.
As used herein, the terms “a”, “an, “, “the” and similar terms used in the context of the present invention (especially in the context of the claims) are to be construed to cover both the singular and plural unless otherwise indicated herein or clearly contradicted by the context. The term “containing” shall cover “comprising”, “essentially consisting of” and “consisting of”
The present invention will be better understood by reference to the figures.
CA). d) The y axis is Young's modulus (GPa), the x axis is hybrid bio plastic type (black bar: amyloid, white bar: monomer, horizontally sparse bar: amyloid FAS and vertically sparse bar: amyloid CA).
Further details on the figures are provided in the experiments below.
In a first aspect, the present invention relates to composite materials (“bioplastic”, “composites”) containing (i.e. “comprising” or “consisting of”) amyloid fibrils, a biodegradable polymer and optionally additives.
As further outlined below, these inventive composite materials add value to the circular economy by valorizing, for example, food waste proteins, such as whey, a byproduct of the dairy industry. The results presented herein demonstrate the potential of composite materials comprising amyloid fibrils (e.g. based on whey) and biodegradable polymers as an efficient, sustainable, and inexpensive solution for alleviating the global plastics production and pollution issue.
It is additionally considered particularly advantageous that the inventive composite materials have physical properties, such as elasticity and toughness, superior to the individual components alone. It was surprisingly found that a composite produced by mixing whey amyloid fibrils and PVA showed significantly better properties compared to films produced by either whey amyloid or PVA alone. The composite films (comprising both, amyloid fibrils and polymer) are significantly more flexible and withstand folding better compared to traditional films (comprising PVA or amyloids alone). At the same time, pure amyloid films are characterized by low mechanical stability, resulting in a film that is extremely brittle, fragmented and poorly water stable, limiting their real-world applications in their pure form.
Moreover, by combining protein amyloid fibrils with the polymer, the biodegradation of the resulting composite material is significantly enhanced.
Additionally, the inventive composites show antioxidant activity that the biodegradable polymer alone does not possess. Without being bound to theory, it is believed that the high number of amino acids exposed on the surface of amyloid fibrils supports this feature.
Additionally, the composite films show high transparency in the visible, combined with UV-blocking properties.
Amyloid fibrils interact e efficiently with the polymers, thanks to their high degree of functionalities, resulting in a more stable, robust, and homogeneous blending compared to protein monomers.
Hence the properties of the inventive composite materials are far superior to those of the individual constituents and also exceed composite materials comprising protein monomers and polymers.
This aspect of the invention shall be explained in further detail below:
Amyloid Fibrils: The term “amyloid fibrils” is generally known in the field and particularly describes fibrils made by proteins or peptides prevalently found in cross beta-sheet secondary structure. Accordingly, the term amyloid fibrils excludes native proteins and other types of non-amyloid protein aggregates.
Amyloid fibrils can be obtained from several different protein sources, collectively amylodogenic proteins, such as vegetable-based proteins and animal-based proteins. In embodiments, amyloid fibrils are obtained from the group of plant-based proteins, preferably:
In embodiments, amyloid fibrils are obtained from the group of animal-based proteins, preferably:
In preferred embodiments, amyloid fibrils are obtained from the group of animal-based proteins, preferably beta-lactoglobulin, and BSA.
In particularly preferred embodiments, amyloid fibrils are obtained from the group of animal-based proteins, preferably from whey.
As an example, the amyloid fibrils are obtained from whey. Whey is a rich source of proteins whose the most abundant is beta-lactoglobulin, a globular protein that can easily self-assembly into amyloid fibrils. Accordingly, the amyloid fibrils are advantageously obtained from whey. Without being bound to theory, it is believed that a broad range of functionalities characterizes the fibrils obtained from these food proteins and, thanks to their remarkable properties that are far superior to those of single monomers (including high stiffness and aspect ratios) they have been found particularly suitable for preparing the inventive composites described herein. Advantageously, the amyloid fibrils have high aspect ratio, preferably with≤10 nm in diameter and >100 nm in length, particular preferably ≤10 nm in diameter and ≥200 nm in length. Advantageously, the amyloid fibrils have a highly charged surface. The term highly charged surfaces is generally known in the field and particularly describes surfaces showing electrophoretic mobilities of the order 2 μm?cm/V?s at pH 4.
Polymer: In line with the present invention, the polymer is biodegradable. The term “biodegradable polymer” is known in the field. It refers to plastics that degrade thanks to the action of microorganisms, such as naturally occurring bacteria, fungi and algae.
Additionally, if a polymer degrades by biological processes into biomass, carbon dioxide, water and inorganic compounds without leaving toxic residues, is defined as “compostable polymer”. So, all compostable plastics belong to the group of biodegradable polymers, but not biodegradable polymers are compostable polymers.
Further, biodegradable polymers distinguish from “bio-based plastics”. While bio-based plastics are produced employing renewable resources rather than fossil fuels not all bio-based plastics are biodegradable, such as those converting renewable resources into building blocks for PET. So, biodegradable polymers distinguish from bio-plastics in that the latter are not necessarily biodegradable.
In embodiments, the polymer is biodegradable according to one or more of the followingSTANDARDS: ISO 14855 or ISO14851 or ISO14852 or ISO17556 or ISO19679.
In embodiments, the polymer is compostable according to one or more of the following norms/regulations: EU13432 (PACKAGING) or EU14995 (NON-PACKAGING) or US ASTM D6400 or ISO17088.
In view of the above, a wide range of biodegradable polymers may be used. Advantageously, they comply with the requirements of biodegradability as given above. Given the manufacturing method, soluble polymers are particularly useful. Such polymers include water-soluble polymers and non-water-soluble polymers.
In embodiments, the polymer is selected from the group of water soluble-polymers, including:
In alternative embodiments, the polymer is selected from the group of non-water soluble polymers, including:
By combining them with amyloid fibrils to give the composite materials as described herein, the disadvantages of protein-based materials, such as difficult to process, poor mechanical properties, poor barrier properties and sensitivity to water/humidity are mitigated.
In embodiments, the polymer is selected from the group of synthetic polymers. Synthetic, biodegradable polymers are known and include Polyvinyl alcohols (PVA), such as fully hydrolyzed PVAs, or Polylactic Acid (PLA, a synthetic polymer from natural monomers). A broad range of molecular weights, as commercially available, may be used in the context or the present invention. Suitable are, for example PVA with 100 000≤ Mw≤500 000 such as Mw approx. 200 000. It was found that composites comprising such synthetic polymers are easily manufactured and processed. Their mechanical and optical properties are advantageous.
In embodiments, the polymer is selected from the group of natural polymers and modified natural polymers, such as polysaccharides, e.g. Methyl cellulose (MC). A broad range of viscosities, as commercially available, may be used in the context or the present invention. Suitable are, for example MC with 100 cP≤viscosity≤1′000 cP such as approx. 400 cP. It was found that composites comprising such polymers are easily manufactured and processed. Their mechanical and optical properties are advantageous.
Additives: It is common in the field to include additive facilitating the manufacturing or to beneficial for influence material's properties. Such additives are commercial items, the type and amount may be selected by the skilled person in line with the intended effect. In embodiments, the additives are selected from biodegradable materials. Additives include plasticizers (such as glycerol and sorbitol); crosslinkers (such as Glutaraldehyde, GA); acids (such as particularly citric acid, boric acid, HCl); antibacterial compounds, (such as silver, sodium azide) and hydrophobic agents (such as waxes, FAS). In embodiments, the inventive composite material is free of additives. Thus, the composite material may consist of amyloid fibrils and biodegradable polymer. In embodiments, the inventive composite materials comprises plasticizers as the only additive. Thus, the composite material may consist of amyloid fibrils, biodegradable polymer and plastizicer. A preferred plasticizer is glycerol.
Composite material: The term composite material is known in the field. According to the present invention, it refers to a material comprising at least two components, a biodegradable polymer and amyloid fibrils. One or more additives may or may not be present. According to this invention, each biodegradable polymer as discussed herein can be combined with each source of protein fibrils as discussed herein.
In preferred embodiments, the composite material comprises a biodegradable polymer and amyloid fibrils as identified in the following list, #1 to #8 (the protein forming the amyloid firbril, i.e. the amylodogenic protein, is identified):
In embodiments, the biodegradable polymer and the amyloid fibrils form a homogeneous network matrix and the additives, if present, are distributed within said matrix. In preferred embodiments, the biodegradable polymer and the amyloid fibrils form a homogeneous double network matrix and the additives, if present, are distributed within said matrix.
In embodiments, the amyloid fibrils are distributed randomly within said polymer.
In embodiments, the amount of polymer ranges from 10 to <66 wt %, preferably ranges from ranges from 20 to <50 wt %. In embodiments, the amount of amyloid fibrils ranges from ≥33 to 90 wt %, preferably ranges from ≥50 to 80 wt %. In embodiments, the amount of additives ranges from 0-40 wt %, preferably 5-35 wt %.
In an embodiment, the invention relates to the use of amyloid fibrils, particularly the use of amyloid fibrils obtained from food waste, in the manufacturing of biodegradable composite materials.
In addition to the chemical composition, the inventive composite material may be characterized by physical parameters.
Advantageously, the composite material has a broad range of surface hydrophobicity, with water contact angles ranging from 20 to 150 degree, preferably 50-120 degree. In embodiments, the water contact angle is above 50 degree. Advantageously, the composite material has a Young's modulus ranging from 0.01 to 4 GPa, depending on the target application and the production process Advantageously, the composite material has a high degree of transparency ranging from 50 to 99.9% visible light transmittance.
The inventive composite materials may be obtained in various forms, generally referred to as solid shaped articles. This particularly depends on step (c) in the process outlined below and includes self-supporting thin films, coatings on a substrate, granules, pellets or casted blocks. In view of many commercial relevant applications, the preferred form is a film. It is considered advantageous that inventive films are obtainable by processes well known in the field, including solution casting or extrusion methods or by hot press methods.
Product-by-process: In a further embodiment, the invention also provides for a composite material obtainable by the method described herein, or obtained according to the method as described herein.
In a second aspect, the invention relates to a method of manufacturing inventive composite materials. Briefly, a composition comprising an amylodogenic protein, for example, beta-lactoglobulin protein, a biodegradable polymer and optionally additives are combined in solution to obtain an initial dispersion. Upon heating and pH adjustment, self-assembly of protein monomers to amyloid fibrils occurs and all components are solubilized. The thus obtained solution may be shaped, e.g. cast, to form a shaped article, e.g. a film, after solvent evaporation. This method of manufacturing is considered simple, scalable and environmentally friendly. This aspect of the invention is depicted in
As will become apparent, and according to the inventive method, dissolved polymer is contacted with amylodogenic protein. The amyloid fibrils are prepared from the amylodogenic protein while dissolved polymer is present. This is in sharp contrast to the previously described methods where amyloid fibrils are prepared from amylodogenic protein prior to the contacting with the polymer or pre-polymer. The inventive method thus avoids a separate preparation step of amyloid fibrils and thus simplifies the overall procedure for obtaining composite materials.
It is understood that the preferences and embodiments disclosed in the first aspect, specifically amyloid fibrils, and amylodogenic proteins, and biodegradable polymers, apply likewise.
Method a: Advantageously, the inventive method comprises the steps of:
The individual process steps are known per se, but not yet applied to the specific starting materials and visualized in
Method B: Advantageously, the inventive method comprises the steps of:
The individual process steps are known per se, but not yet applied to the specific starting materials. It is advantageous if the above organic solvent and water do form a miscible phase.
It is considered particularly advantageous that important properties of the inventive composite material, including density, stiffness and color, may be tuned in s simple way by adjusting the individual process steps.
It is considered particularly advantageous that the method provides composite materials with well-organized structures and unprecedented properties.
It is further considered particularly advantageous that the obtained materials have unique optical properties, such as high transparency.
In embodiments, the invention relates to a method from manufacturing composite materials as described herein in the form of a film. The method is considered scalable and straightforward (as suitable for existing equipment) and environmentally friendly (as water based). Specifically, WPI (whey protein isolate) is dispersed in pH 2 water together with glycerol and a water-soluble polymer selected from PVA or other soluble polymers. The solution is then heated to thereby solubilize all the components homogeneously and convert beta-lactoglobulin protein into self-assembled amyloid fibrils (e.g. 90° C. for 5 hours). This solution is cast onto a substrate followed by solved evaporation to thereby obtain freestanding homogeneous and transparent films containing the inventive composite material, with properties superior to those of the individual components.
Water soluble polymers: In case the polymer is water soluble, water is used as a solvent. These starting materials are known per se. Combining them and adjusting pH to 0.5-4 such as pH=2 is entirely conventional. Non-Water soluble Polymers: In case the polymer is non-water soluble, an organic solvent for that polymer, such as DMSO, THE, DMF or ethanol is used, either alone or in combination. In this embodiment, amyloid aqueous solution is prepared separately according to (a) and (b); than it is mixed with the biopolymer separately dissolved in a polar solvent and the resulting mixture is subjected to step (c).
Converting amylodogenic protein monomers to amyloid fibrils by application of heat and to thereby obtain a solution is a process known in the field. Advantageously, the reaction mixture is stirred. Advantageously, the reaction mixture is heated to 70-95° C. for 1-10 hrs, preferably 90° C./5 hrs. This step may be terminated by quenching.
Again, processing a solution comprising dissolved polymer into a solid is known in the field. Due to the properties of polymer and amyloid fibrils, common casting and extruding technologies may be applied. Suitably, a thin film is cast and dried under ambient or controlled conditions, e.g. by application of moderate heat and/or reduced pressure.
The inventive process may be accomplished by further steps, e.g. preceding step (a) or following step (c), including purification, further processing, assembling and other process steps known to the skilled person. In embodiments, the inventive method comprises one or more finishing steps (d), including chemical treatment e.g. a cross-linking agent in alcoholic solution.
As shown above, the manufacturing is very flexible. The chemical, mechanical and optical properties of the obtained composite materials can be tailored by the changing the preparation conditions such as concentration of precursors, drying temperature and substrate type and texture. For example, hydrophobicity and mechanical stability of inventive composites can be conveniently tuned by chemical treatment inducing crosslinking within the fibrils and polymer domains.
In a third aspect, the invention also relates to various uses of the inventive composite materials and to articles comprising or consisting of a composite material as described herein. Compared to other bioplastics, the inventive composite materials present a remarkable water stability and hydrophobic behavior, allowing these materials to be suitable for many applications to thereby replace traditional plastics.
Accordingly, the invention provides for an article, selected from the group consisting of foils, laminates, bags, containers, and tubes.
In embodiments of the invention, the inventive composite material is present as a shaped article, such as a semi-finished product. This is typically the case once manufacturing is completed. In this form, the inventive composites are typically in the form of foils or extrudates.
In a further embodiment of the invention, the inventive composite is present as a coating on a substrate. A broad range of substrates may be coated, depending on the intended use of the inventive composite. The coating may be the top coating. Accordingly, the invention also provides for an article comprising a substrate and a coating, said coating consisting of an inventive composite material as described herein. Such articles include packaging materials.
In a further embodiment of the invention, the inventive composite is present as a packaging material, particularly as a packaging material for fresh food products; as a packaging material for beverages including hot and cold beverages; as a packaging material for processed food/pre-cooked products; as a packaging material for snack products, as a packaging material for non-food products, such as electronics, or clothes.
To further illustrate the invention, the following examples are provided. These examples are provided with no intent to limit the scope of the invention.
Whey protein isolate (WPI) was supplied from Fonterra, New Zealand. Polyvinyl alcohol (PVA, fully hydrolyzed, Mw approx. 200000) and Hydrochloric acid (36%) were purchased from Merck. Methyl cellulose (MC) (viscosity: 400 cP), Glycerol (299.5%), Citric acid (CA) (299.5%), 1H, 1H, 2H, 2H-Perfluorooctyltriethoxysilane (FAS), 2, 2′-azinobis (ethyl-2, 3-dihydrobenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), and Tenax® porous polymer adsorbent (60-80 mesh) were provided from Sigma Aldrich
example 1, HAm-PVA: For fabricating hybrid amyloid (HAm) fibrils film, 4 g of WPI first was dissolved in 100 ml of water. Then the pH of the solution was adjusted to 2 and 2 g of Glycerol, as a plasticizer, was dispersed in the solution. For hybrid amyloid fibrils films with PVA and MC, 2 g of each compound was added to the solution. To convert the WPI monomers to amyloid fibrils and dissolving the biodegradable polymer, the solution was stirred and heated at 90° C. for 5 h. After the incubation, the solution cast immediately on a petri dish to dry at room temperature.
example 1.1, HAm-PVA treated with CA: For the study of the effect of CA in film properties, 1.5 g of it was added to solutions before the fibrilization process.
example 1.2, HAm-PVA coated with FAS: Moreover, for fabricating more hydrophobic films, they were placed in an ethanolic solution containing FAS (0.5 wt %) for 1 h. Subsequently, the films were dried under room temperature to obtain the FAS-coated hybrid amyloid films.
example 2: HAm-MC: The generality of the approach for fabricating different composite materials, PVA is replaced by Methylcellulose (MC, methyl ether of cellulose), cf.
The details of composition and treatment are listed in Table. 1.
To characterize the morphologies of amyloid fibrils and their composite materials in the form of films, Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used. For AFM, the solutions were dried onto cleaved mica and analyzed by applying the tapping mode. A Hitachi SU5000 scanning electron microscope characterized the structure and properties of hybrid bioplastic films. Small pieces of films were attached to stubs with paste and sputter-coated with 5 nm of platinum/palladium under planetary rotational movement (Safematic, CCU-10, Switzerland) before imaging.
The mechanical properties of films were evaluated by measuring tensile strength and elongation using a Z010 (Zwick) equipped with a 100 N load cell. The stress (o)-strain (a) curves were obtained at room temperature. The Young's modulus was calculated from the stress-strain curves.
The water contact angle of the films was recorded by Nikon D300 digital camera at 25° C. and relative humidity of 50%. To shed light on the interaction of films with water, their weight loss, and water absorption after immersing in the water and at different time intervals were measured.
The interaction with water is further investigated and the results are summarized in
Panel b: The water adsorption measurements resulted in very similar behavior in the films based on amyloid fibrils independently by the treatment and all the films absorbed around 225% of water after 24 hours of immersion. The swelling, however, increased significantly in the film obtained by WPI monomers, reaching water adsorption values of around 325%. The low performances of monomer based films are supposed to be related to the hydrophilic nature of the protein native state but also to the surface properties of these films that, as already discussed above (see also
The antioxidant activity of film was determined by the spectrophotometric method described by Kusznierewicz et al. Briefly, the stock solution of ABTS with the concentration of 7 mM was diluted with water to display the absorbance of 0.7 at 734 nm. Then 4.5 mL of ABTS solution was combined with a piece of film (10 mg). After 20 min reaction time, the film was removed, and the solution was transferred to a cuvette, and its absorbance was measured at 734 nm with the use of a UV-vis spectrophotometer (Cary 100, Agilent Technology). Finally, the amount of ABTS radicals scavenged by 1 g of the film was calculated based on the Beer-Lambert-Bouguer Law:
where, ScABTS is the amount of scavenged ABTS (μmol), VABTS is the volume of stock solution of ABTS added to the film (mL), AO is the absorbance of the initial ABTS solution; Af is the absorbance of the radical solution after reaction time; ε is the ABTS molar extinction coefficient (16,000 M-1 cm-1 at 734 nm), 1 is the optical path of the cuvette (1 cm) and m is the film mass (g) 33. The inventive hybrid amyloid fibril films showed excellent antioxidant activity by scavenging 150-300 μmol ABTS/g.
The food-contact migration properties of the bioplastic films were evaluated based on EU technical guidelines for compliance testing in the framework of the plastic FCM Regulation (EU) No 10/201134. To assess the possible migration of molecules from the films to the food, Tenax® was used as a dry food simulant. In a clean glass petri dish, a square-shape film with a dimension of 2 cm was placed between two layers of Tenax® powder (40 mg below and 40 mg above the sample) and stored in the oven for 2 h at 70° C. The overall food migration was calculated by the mass difference of Tenax® before and after the treatment resulting in migration values below the EU limit.
Further composite materials in the form of a film example 3.1, beta-lactoglobulin/PVA: The hybrid whey bioplastics were prepared by directly mixing liquid whey, from the byproduct of the dairy industry, with the biodegradable polymer PVA. Then, to induce the assembly of the protein amyloid fibrils, the pH was adjusted to 2, and the mixture was heated at 90° C. for 5 h. example 3.2, rapeseed cake/PVA: For hybrid bioplastics from rapeseed cake, first, the impurities of the cake were removed via a filtration step. Then, the protein-rich supernatant was mixed with PVA. Fibrilization of rapeseed protein was achieved with the same condition as for whey, ex. 3.1. Both films of ex. 3 were prepared by solution casting method and drying at room temperature. The composites of ex. 3.1 are shown in
examples 4.1 to 4.3: Similar to ex. 3, the following composites in the form of a film were obtained, using different purity grades of whey protein isolate (WPI, high purity), whey protein concentrate (WPC, processed), and liquid whey (sweet whey, unprocessed). The results are summarized in
As clearly shown by the examples and data provided, amyloid fibrils are a suitable building block for developing composite materials jointly with a biodegradable polymer. To do so, in situ fibrilization of protein monomers, e.g. whey, took place in the presence of a plasticizer and a biodegradable plastic, such as PVA and MC. The resultant films were transparent, flexible, and exhibited mechanical and water stabilities superior to the individual components. The films can be prepared from cheap bio-based and biodegradable sources, point to their affordability and environment friendliness for a broad range of applications.
Further, as surprisingly found in ex. 3, the protocol for producing amyloid fibrils-based bioplastics from wastes or sidestreams results in films with quality and properties comparable to those produced from pure protein sources. Additionally, having unpurified whey allows fabricating flexible films without using plasticizer (without being bound to theory, this may be related to the plasticizing properties of lactose, contained in this byproduct).
| Number | Date | Country | Kind |
|---|---|---|---|
| 21173061.9 | May 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/062215 | 5/5/2022 | WO |
