Additives for degradation modification of polyhydroxyalkanoate polymers and methods of use thereof

Abstract

Described herein are biodegradable compositions and methods of using thereof. Such biodegradable compositions exhibit controllable or modifiable degradation rates by the inclusion of one or more additives therein. Such biodegradable compositions can be used to form articles and products which can be degraded by microbes, such as in marine environments.

Description

[0001] ADDITIVES FOR DEGRADATION MODIFICATION OF POLYHYDROXYALKANOATE POLYMERS AND METHODS OF USE THEREOF

[0002] CROSS-REFERENCED TO RELATED APPLICATIONS

[0003] This application claims the benefit of and priority to U.S. Provisional Application No. 63 / 555,611, filed February 20, 2024, and U.S. Provisional Application No. 63 / 683,522, filed August 15, 2024, which are hereby incorporated herein by reference in their entireties.

[0004] FIELD OF THE INVENTION

[0005] The disclosed invention is generally in the field of biodegradable compositions with modified or controlled degradation of polyhydroxyalkanoate-based plastics, and methods of using thereof.

[0006] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0007] This invention was made with Government support under Grant No. 2230641 awarded by the National Science Foundation. The Government has certain rights in the invention.

[0008] BACKGROUND OF THE INVENTION

[0009] The detrimental effects of plastic waste are becoming more well-known, especially regarding the ocean. Both consumers and governments recognize and have called for alternatives to plastic for products that will not persist in the environment or be toxic when they degrade.

[0010] Most compostable materials are made to be processed in industrial composting facilities and do not degrade quickly, if at all, in cold, dark marine environments. Even materials that can be composted without industrial processing may not degrade in the ocean.

[0011] It can be expected that regulation of plastics and their usage will result in increased usage of bioplastics, which can be biodegradable alternatives to conventional plastics. Demand for eco- friendly products, or uses where the bioplastic should otherwise degrade quickly, is expected to increase over time.

[0012] However, controlling or modifying the degradation of bioplastics presents challenges, particularly for their full degradation in certain environments, such as in marine environments, in desired timeframes. Accordingly, there remains a need for ways to modify and / or control the degradation rate of bioplastics.

[0013] Therefore, it is an object of the present invention to provide biodegradable compositions having degradation rates which are modifiable or controllable.

[0014] It is a further object of the present invention to provide methods of using such compositions.

[0015] SUMMARY OF THE INVENTION

[0016] Described herein are biodegradable compositions and methods of using thereof. For instance, articles and products made from such biodegradable compositions may end up in marine environments where marine microbes are able to efficiently degrade these articles and products due to the presence of the additive(s) used to form them. In one instance, such biodegradable compositions can include: at least one polyhydroxyalkanoate; and at least one additive selected from:

[0017] (i) one or more amino acids;

[0018] (ii) one or more macronutrients; or

[0019] (iii) one or more micronutrients; wherein the concentration of the at least one additive is effective to modify the degradation rate of the polyhydroxyalkanoate by microbes in a marine environment, as compared to the degradation rate of the polyhydroxyalkanoate in the absence of the at least one additive.

[0020] Formation of such biodegradable compositions can be achieved by combining at least one polyhydroxyalkanoate and at least one additive, such as by blending these components to form the composition.

[0021] In certain instances, the polyhydroxy alkanoate is polyhydroxybutyrate, such as poly-3 - hydroxybutyrate (P3HB).

[0022] In some instances, more than one additive is present and the additives can include: at least two selections from (i)-(iii); or the at least one additive includes a combination of species from (i), (ii), and (iii).

[0023] In certain instances, at least one additive is present in the composition at a concentration of up to about 5%, 6%, 7%, 8%, 9%, 10%, or higher of the total mass of the biodegradable composition. In certain instances, the at least one additive is present in the composition at a concentration ranging from about 0.01% to 10% or 0.01% to 5% of the total mass of the biodegradable composition, as well as individual concentration values or sub-ranges contained within the aforementioned ranges.

[0024] The biodegradable compositions described herein can be used for various applications. For instance, articles or products can be formed from the biodegradable compositions described herein. In one non-limiting instance, a method of forming an article or product can include the steps of: extruding, casting, printing, rotomolding, blow molding, and / or injection molding a biodegradable composition described herein to form an article or product.

[0025] BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 shows a bar graph of the fold-enhancement in biodegradation of biodegradable compositions (as detailed in Table 1), relative to a standard injection-molding grade polyhydroxybutyrate (PHB), where values greater than 1 indicate an enhancement in biodegradation rate. Polybutylene succinate (PBS) and poly(lactic acid) (PLA), two other biopolymers, were also evaluated.

[0027] Figure 2 shows representative carbon dioxide accumulation curves generated during respirometry used to calculate the biodegradation enhancements. “IM” refers to a standard injection molding blend of polyhydroxybutyrate, Formulation 116 corresponds with Sample Formula 116 as described in Table 1.

[0028] DETAILED DESCRIPTION OF THE INVENTION

[0029] Biodegradable compositions and methods of using thereof are described herein.

[0030] I. Definitions

[0031] Biodegradable,” as used herein, refers to a material or composition that can be degraded or eroded by microbes into smaller units or chemical species, such as carbon dioxide, of the original material or composition and that are capable of being metabolized, eliminated, or excreted by such microbes.

[0032] "Macronutrient," as used herein refers to essential nutrients required by microorganisms in significant amounts to support their growth, metabolism, and reproduction. Such essential nutrients typically include nitrogen (N) and phosphorus (P). Microbes, including bacteria, require such macronutrients to fulfill their nutritional needs. Macronutrients are obtained from the surrounding environment.

[0033] "Micronutrient," as used herein refers to essential nutrients that microorganisms require to support their growth, development, and metabolic activities. Typically, micronutrients are needed in lower quantities compared to macronutrients, but they play important roles in various cellular processes. Micronutrients include a variety of elements (such as iron or cobalt) and compounds (such as vitamins) that are essential for the proper functioning of microbial cells.

[0034] An “alkyl group” is understood to mean a radical having 1 to 12 carbon atoms. The alkyl radical may be linear, branched, or unbranched hydrocarbon chain, which may optionally be interrupted by one or more heteroatoms, such as N, O, or S. Heteroatoms may have hydrogen substituents and / or any permissible substituents of organic compounds in order to satisfy the valences of the heteroatoms. The alkyl group may optionally be substituted by one or more of the substituents. Exemplary alkyl radicals include, without limitation, methyl, ethyl, i-propyl, n- propyl, i-butyl, n-butyl, t-butyl, sec -butyl, i-pentyl, n-pentyl, sec-pentyl, neopentyl, n-hexyl, i- hexyl, sec -hexyl, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl.

[0035] Numerical ranges disclosed in the present application include, but are not limited to, ranges of integers, ranges of concentrations, ranges of times, amongst other ranges disclosed below. The disclosed ranges, disclose individually each possible number that such a range could reasonably encompass, as well as any sub-ranges and combinations of sub-ranges encompassed therein. For example, disclosure of a range of concentrations is intended to disclose individually every possible value that such a range could encompass, consistent with the disclosure herein. For example, a concentration range of about 5 wt% to 10 wt% also discloses each weight concentration within the range individually (e.g., 5, 5.6, 6, 6.8, 7, 7.1, 8, 8.4, 9, 9.9, 10, 10.11 wt%, amongst others), as well as any sub-range contained therein (e.g., about 5.2 to 8.5 wt%).

[0036] Use of the term "about" is intended to describe values either above or below the stated value, which the term “about” modifies, in a range of approx. + / - 10%; in other instances, the values may range in value either above or below the stated value in a range of approx. + / - 5%. When the term "about" is used before a range of numbers (i.e., about 1-5) or before a series of numbers (i.e., about 1, 2, 3, 4, etc.) it is intended to modify both ends of the range of numbers and / or each of the numbers recited in the entire series, unless specified otherwise.

[0037] IL Biodegradable Compositions

[0038] Polyhydroxyalkanoate-based polymers can be synthesized by microbes, such as bacteria, as a way to store carbon. Moreover, such microbes can also consume polyhydroxyalkanoate- based polymers. As described herein, analysis of microbes and their metabolism has been used to identify additive(s) that can assist such microbes with consumption and degradation of certain bioplastics, such as polyhydroxyalkanoate-based polymers, by altering the degradation rates compared to the degradation of the same bioplastics in the absence of such additive(s). The additive(s) can be blended with polyhydroxyalkanoate -based polymers prior to casting these biopolymers to form articles and products. In some instances, such articles and products may end up in marine environments where, for instance, marine microbes are able to efficiently degrade these articles and products due to the presence of the additive(s) used to form them.

[0039] For example, such compositions can include: at least one polyhydroxyalkanoate; and at least one additive selected from:

[0040] (i) one or more amino acids;

[0041] (ii) one or more macronutrients; or

[0042] (iii) one or more micronutrients; wherein the concentration of the at least one additive is effective to modify the degradation rate of the polyhydroxyalkanoate by microbes in a marine environment, as compared to the degradation rate of the polyhydroxyalkanoate in the absence of the at least one additive.

[0043] Formation of such biodegradable compositions can be achieved by combining at least one polyhydroxyalkanoate and at least one additive, such as by blending these components to form the composition. The polyhydroxyalkanoate is typically provided in the form of a solid having any suitable size and shape, such as in the form of pellets. In some instances, the polyhydroxyalkanoate and at least one additive are fed separately through loss-in-weight feeders and blended in a twin screw extruder to produce a combined strand which is subsequently pelletized and can be used for injection molding. Typically, these components of the blend are dried overnight prior to blending and extrusion. In some instances, drying is performed by placing the components in an oven set to a temperature of about 50 to 80 °C, 50 to 75 °C, or 60 to 70 °C, or any individual temperature value or sub-range contained within the aforementioned ranges. In certain instances, the oven is set to a temperature of about 70 °C. In some instances, the biodegradable compositions are provided as compounded pellets or nurdles.

[0044] Optionally, prior to blending the polyhydroxyalkanoate with at least one additive, the polyhydroxyalkanoate is subject to one or more pre-processing steps, such as grounding or pulverizing to form a powdered PHA. Optionally, particular sizes and size ranges of particles in the powdered PHA are separated and selected for blending with the additive(s). For example, a PHA powder can be sieved to select particles having selected average size ranges.

[0045] In some instances, at least one polyhydroxyalkanoate biopolymer is pelletized and may be provided as pellets of 3-5 mm in size, which can be ground into a powder form. In some instances, the powder may be sieved to select for particles having an average size ranging from between about 100 to 1000 pm, 250 to 750 pm, 400 to 700 pm, or 500 to 600 pm in size, as well as individual size values or sub-ranges contained within the aforementioned ranges. In some instances, the particles may have an average size ranging from between about 500 to 600 m in size, as well as individual size values or sub-ranges contained within the aforementioned range.

[0046] In certain instances, the polyhydroxyalkanoate is polyhydroxybutyrate, optionally the polyhydroxybutyrate is poly-3-hydroxybutyrate (P3HB).

[0047] In other instances, the polyhydroxyalkanoate has a chemical structure as shown below: where n is an integer value ranging from between about 2 to 10,000, 100 to 10,000, or 1,000 to 10,000, as well as individual values or sub-ranges contained within the aforementioned ranges.

[0048] In some instances, the polyhydroxyalkanoate has a chemical structure according to Formula I below:

[0049] Formula (I) where R is a C1-C12 alkyl group; and where m is an integer value ranging from between about 2 to 10,000, 100 to 10,000, or 1,000 to 10,000, as well as individual values or sub-ranges contained within the aforementioned ranges.

[0050] In yet other instances, the polyhydroxyalkanoate can be a co-polymer of at least two segments, such as of Formula (I) above, having different R alkyl group lengths. Such polyhydroxyalkanoate-based copolymers are known to the person of ordinary skill in the art, as well as methods for synthesizing thereof. In some instances, the polyhydroxyalkanoate-based copolymers include combinations of two or more, optionally three or more, optionally four or more monomer repeat units derived from 3-hydroxybutyrate, 4-hydroxybutyrate, 3- hydroxyvalerate, 3 -hydroxyhexanotate, 3-hydroxyheptanoate, 3-hydroxyoctanoate, 3- hydroxy nonanoate, 3-hydroxydecanoate, 3-hydroxy undecanoate, and / o 3-hydroxydodecanoate. The monomer repeat units making up a copolymer may be present in at molar amounts ranging from greater than 0 to less than about 100 mol% of the copolymer, where it is understood that at least two different types of monomer repeat units are present in a copolymer chain and the sum of all of the monomer repeat units sums to 100 mol% of the polymer chain. In some instances, a polyhydroxyalkanoate-based copolymer may contain greater than 0 to 100 mol% 3- hydroxybutyrate, greater than 0 to 50 mol% 4-hyrdoxybutyrate, greater than 0 to 50 mol% 3- hydroxyvalerate, greater than 0 to 50 mol% 3 -hydroxyhexanoate, greater than 0 to 50 mol% 3- hydroxyheptanoate, greater than 0 to 50 mol% 3-hydroxyoctanoate, greater than 0 to 50 mol% 3- hydroxynonanoate, greater than 0 to 50 mol% 3-hydroxydecanoate, greater than 0 to 50 mol% 3- hydroxy undecanoate, greater than 0 to 50 mol% 3-hydroxydodecanoate, greater than 0 to 25 mol% 4-hyrdoxybutyrate, greater than 0 to 25 mol% 3 -hydroxy valerate, greater than 0 to 25 mol% 3 -hydroxyhexanoate, greater than 0 to 25 mol% 3-hydroxyheptanoate, greater than 0 to 25 mol% 3-hydroxyoctanoate, greater than 0 to 25 mol% 3 -hydroxynonanoate, greater than 0 to 50 mol% 3-hydroxydecanoate, greater than 0 to 25 mol% 3-hydroxy undecanoate, and / or greater than 0 to 25mol% 3-hydroxydodecanoate. In some instances, the copolymer can be poly(3- hydroxybutyrate-co-3-hydroxy valerate).

[0051] In some instances, the presence of the at least one additive in the biodegradable composition is effective to increase the degradation rate by at least about 1 %, 2%, 3%, 4%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or greater, as compared to the degradation rate of the polyhydroxyalkanoate in the absence of the at least one additive. In certain instances, the presence of the at least one additive in the biodegradable composition is effective to increase the degradation rate by at least about 2 times, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times, 9 times, or 10 times, as compared to the degradation rate of the polyhydroxyalkanoate in the absence of the at least one additive.

[0052] In some instances, the degradation rate is increased by at least about 10% greater, as compared to the degradation rate of the polyhydroxyalkanoate in the absence of the additive(s). In certain instances, the degradation rate is increased from between about 1% to 100%, as compared to the degradation rate of the polyhydroxyalkanoate in the absence of the additive(s).

[0053] In yet other instances, the degradation rate may be decreased by at least about 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or greater, compared to the degradation rate of the polyhydroxyalkanoate in the absence of the additive(s). In certain instances, the degradation rate may be decreased from between about 1% to 100%, as compared to the degradation rate of the polyhydroxyalkanoate in the absence of the additive(s). In some instances, more than one additive is present and the additives can include: at least two selections from (i)-(iii); or the at least one additive includes a combination of species from (i), (ii), and (iii).

[0054] In certain instances, the microbes are marine microbes. In some instances, the selection of at least one additive, or combinations thereof, may be made in view of presence or lack of such additives in the marine environment. For instance, it may be desirable to include an additive of types (i)-(iii) in a composition based on a marine environment which lacks or is deficient in the presence of species of such additive(s) of types (i)-(iii).

[0055] In certain instances, at least one additive is present in the composition at a concentration of up to about 5%, 6%, 7%, 8%, 9%, 10% wt / wt, or higher of the total mass of the biodegradable composition. The total mass of the biodegradable composition refers to the sum of the masses of the polyhydroxyalkanoate and all of the additives in the biodegradable composition. References to “concentration by weight” or “wt / wt %” are used interchangeably herein to refer to the mass / mass % or concentrations by mass, such as by referring to a concentration by % of the total mass of the biodegradable composition. In certain instances, the at least one additive is present in the composition at a concentration ranging from about 0.01 % to 10% or 0.01 % to 5% wt / wt of the total mass of the biodegradable composition, as well as individual concentration values or sub-ranges contained within the aforementioned ranges. In certain instances, the total amount of additives present in the composition is at a concentration of up to about 5%, 6%, 7%, 8%, 9%, 10% wt / wt, or higher of the total mass of the biodegradable composition. In certain instances, the total amount of additives present in the composition is at a concentration of greater than about 0.01%, 0.05%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% wt / wt, of the total mass of the biodegradable composition. Combinations of the above-referenced ranges are also possible (e.g., greater than about 0.5% and up to about 6% wt / wt.). In certain instances, the total amount of additives present in the composition is in a concentration ranging from between about 0.01% to 10%, 0.01% to 7.5%, 0.01% to 9%, 0.01% to 5%, 0.01% to 2.5%, 0.01% to 1%, 0.01% to 0.5%, 1 to 2%, 1 to 3%, 2 to 3%, 2 to 5%, 3 to 4%, 3 to 5%, or 4 to 5% wt / wt, of the total mass of the biodegradable composition, as well as individual concentration values or subranges contained within the aforementioned ranges. The concentration by weight of the total amount of additives in the composition (also referred to herein at the concentration of total additives) refers to the sum of the masses of all of the additives that are blended with the polyhydroxyalkanoate divided by the total mass of the biodegradable composition times 100. a. Amino Acids

[0056] In certain instances, the biodegradable composition can contain one or more amino acids. In some instances, the one or more amino acids are present at a concentration in a range of between about 0.01% to 10%, 0.05% to 5%, 0.01 to 0.5%, 0.02 to 0.5%, 0.03 to 0.5%, 0.04 to 0.5%, 0.05 to 0.5%, 0.06 to 0.5%, 0.07 to 0.5%, 0.08 to 0.5%, 0.09 to 0.5%, 0.01 to 1%, 0.02 to 1%, 0.03 to 1%, 0.04 to 1%, 0.05 to 1%, 0.06 to 1%, 0.07 to 1%, 0.08 to 1%, or 0.09 to 1%, of the total mass of the biodegradable composition, as well as individual concentration values or sub-ranges contained within the aforementioned ranges.

[0057] There is no particular restriction on the amino acid(s) that can be included in the composition. In some instances, the one or more amino acids are naturally occurring amino acids and can be selected from phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, histidine, alanine, arginine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, proline, serine, tyrosine, and combinations thereof. In still other instances, the amino acid(s) may also be selected from non-naturally occurring amino acids known to the skilled person.

[0058] In certain instances, the biodegradable composition can include tyrosine and / or phenylalanine. b. Macronutrients

[0059] In certain instances, the biodegradable composition can contain one or more macronutrients. The one or more macronutrients can be present in the biodegradable composition at a concentration in a range of between about 0.1% to 10%, 0.1% to 5%, 1% to 10%, 1% to 7.5%, 1% to 5%, 1% to 4%, 1% to 3%, 1% to 2%, 0.1% to 1%, 2% to 5%, 3 to 5%, or 4 to 5% of the total mass of the biodegradable composition, as well as individual concentration values or sub-ranges contained within the aforementioned ranges.

[0060] In some instances, the macronutrients can be selected from ammonium sulfate, sodium phosphate, potassium phosphate, ammonium chloride, and combinations thereof. In some cases, where the macronutrient includes ammonium chloride, the ammonium chloride is in the face centered cubic (fee) form. In certain instances, the one or more macronutrients do not include ammonium chloride in the fee form or are substantially free of ammonium chloride in the fee form, and consequently the biodegradable composition is free of or substantially free of ammonium chloride in the fee form. In certain instances, the one or more macronutrients do not include ammonium chloride or are substantially free of ammonium chloride, and consequently the biodegradable composition is free of or substantially free of ammonium chloride. “Substantially free,” as used herein, refers to the biodegradable composition having less than about 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, or 0.1% by total weight of the composition of ammonium chloride therein.

[0061] In certain instances, the biodegradable compositions include a nitrogen (N) and a phosphorus (P) source. c. Micronutrients

[0062] In certain instances, the biodegradable composition can contain one or more micronutrients. The one or more micronutrients can be present in the biodegradable composition at a concentration in a range of between about 0.01% to 10% or 0.01% to 5% of the total mass of the biodegradable composition, as well as individual concentration values or sub-ranges contained within the aforementioned ranges, such as between about 0.01% to 0.1%, 0.01% to 0.5%, 0.1% to 0.5%, 0.1% to 1.0%, 0.1 to 10%, 1% to 5%, or 1% to 10% of the total mass of the biodegradable composition.

[0063] In some instances, the biodegradable composition can include one or more micronutrients, such as iron or cobalt metal. Optionally the micronutrient is a complex of the metal by a chelating agent, such as iron or cobalt metal that is complexed by a chelating agent. In certain instances, the chelating agent is ethylenediaminetetraacetic acid (EDTA).

[0064] In certain instances, the one or more micronutrients include a vitamin, where the vitamin can be, without limitation, cobalamin / vitamin B12 and / or thiamine. d. Non-Limiting Exemplary Additives

[0065] One or more of the additives described above can be used alone or in combination in the biodegradable composition. Several non-limiting exemplary additive(s) which may be blended with polyhydroxyalkanoate-based polymers are listed below. In the instances provided below, the combinations or single additives specified are understood to be the only additives present in the biodegradable composition. Suitable ranges and amounts of such additives are as described in Section II.

[0066] In one instance, a combination of all the naturally occurring amino acids are used as the additives and blended with a polyhydroxyalkanoate-based polymer to form the biodegradable composition.

[0067] In a second instance, tyrosine, phenylalanine, and iron-chelated by EDTA are used as the additives and blended with a polyhydroxyalkanoate-based polymer to form the biodegradable composition. Optionally, other suitable source(s) of N and P, such as ammonium chloride, potassium phosphate, and / or sodium phosphate may be present in the biodegradable composition. In a third instance, tyrosine and phenylalanine may be used as the additives and blended with a polyhydroxyalkanoate-based polymer.

[0068] In a fourth instance, ammonium chloride may be used as an additive and blended with a polyhydroxyalkanoate-based polymer.

[0069] In a fifth instance, sodium phosphate may be used as an additive and blended with a polyhydroxyalkanoate-based polymer.

[0070] In a sixth instance, iron-chelated by EDTA may be used as an additive and blended with a polyhydroxyalkanoate-based polymer.

[0071] In a seventh instance, vitamin B 12 may be used as an additive and blended with a polyhydroxyalkanoate-based polymer.

[0072] In an eighth instance, serine, histidine, and aspartic acid may be used as the additives and blended with a polyhydroxyalkanoate-based polymer.

[0073] In a ninth instance, serine, histidine, aspartic acid, and iron-chelated by EDTA may be used as the additives and blended with a polyhydroxyalkanoate-based polymer. Optionally, other suitable source(s) of N and P, such as ammonium chloride, potassium phosphate, and / or sodium phosphate may be present in the biodegradable composition.

[0074] In a tenth instance, lysine, histidine, and serine may be used as the additives and blended with a polyhydroxyalkanoate-based polymer.

[0075] In an eleventh instance, lysine, histidine, serine, and iron-chelated by EDTA may be used as the additives and blended with a polyhydroxyalkanoate-based polymer. Optionally, other suitable source(s) of N and P, such as ammonium chloride, potassium phosphate, and / or sodium phosphate, may be present in the biodegradable composition.

[0076] In a twelfth instance, leucine, arginine, and tryptophan may be used as the additives and blended with a polyhydroxyalkanoate-based polymer.

[0077] In a thirteenth instance, leucine, arginine, tryptophan, and iron-chelated by EDTA may be used as the additives and blended with a polyhydroxyalkanoate-based polymer. Optionally, other suitable source(s) of N and P, such as ammonium chloride, potassium phosphate, and / or sodium phosphate, may be present in the biodegradable composition.

[0078] In a fourteenth instance, isoleucine, methionine, and threonine may be used as the additives and blended with a polyhydroxyalkanoate-based polymer.

[0079] In a fifteenth instance, isoleucine, methionine, threonine, and iron-chelated by EDTA may be used as the additives and blended with a polyhydroxyalkanoate-based polymer. Optionally, other suitable source(s) of N and P, such as ammonium chloride, potassium phosphate, and / or sodium phosphate, may be present in the biodegradable composition. In a sixteenth instance, valine, proline, and cysteine may be used as the additives and blended with a polyhydroxyalkanoate-based polymer.

[0080] In a seventeenth instance, valine, proline, cysteine, and iron-chelated by EDTA may be used as the additives and blended with a polyhydroxyalkanoate-based polymer. Optionally, other suitable source(s) of N and P, such as ammonium chloride, potassium phosphate, and / or sodium phosphate, may be present in the biodegradable composition.

[0081] In an eighteenth instance, aspartic acid, glycine, and alanine may be used as the additives and blended with a polyhydroxyalkanoate -based polymer.

[0082] In a nineteenth instance, aspartic acid, glycine, alanine, and iron-chelated by EDTA may be used as the additives and blended with a polyhydroxyalkanoate-based polymer. Optionally, other suitable source(s) of N and P, such as ammonium chloride, potassium phosphate, and / or sodium phosphate, may be present in the biodegradable composition.

[0083] In a twentieth instance, asparagine, glycine, and glutamine may be used as the additives and blended with a polyhydroxyalkanoate -based polymer.

[0084] In a twenty-first instance, asparagine, glycine, glutamine, and iron-chelated by EDTA may be used as the additives and blended with a polyhydroxyalkanoate -based polymer. Optionally, other suitable source(s) of N and P, such as ammonium chloride, potassium phosphate, and / or sodium phosphate, may be present in the biodegradable composition.

[0085] In a twenty-second instance, a combination of ammonium chloride and / or potassium phosphate and iron-chelated by EDTA are used as the additives and blended with a polyhydroxyalkanoate-based polymer to form the biodegradable composition. Optionally, sodium phosphate may be present in the biodegradable composition, in place of or in addition to potassium phosphate. e. Evaluation of Degradation Rate of Biodegradable Compositions

[0086] The degradation rate of biodegradable compositions and comparative control samples, which do not include any additives, can be accomplished using known methods. In one instance, carbon dioxide-based respirometry can be used to evaluate the degradation rate of biodegradable compositions and comparative controls. For instance, biodegradable compositions and comparative control(s) can be exposed to microbes, such as found in marine environments (such as seawater), and respirometry can be used to analyze and measure the gases of each sample headspace for changes in oxygen and carbon dioxide concentrations. Based on the concentration changes of carbon dioxide, for instance, it is possible to calculate the degree of increase / enhancement in the degradation rate, as compared to a baseline degradation rate. III. Methods of Using

[0087] The biodegradable compositions described herein can be used for various applications. For instance, articles or products can be formed from the biodegradable compositions described herein.

[0088] In one non-limiting instance, a method of forming an article or product can include the steps of: extruding, casting, printing, rotomolding, blow molding, and / or injection molding a biodegradable composition described herein to form an article or product.

[0089] In certain instances, the method involves printing the biodegradable composition where the printing step is or includes 3D printing.

[0090] The person of ordinary skill in the art is understood to be familiar with various techniques and procedures for extruding, casting, printing, rotomolding, blow molding, and / or injection molding of biodegradable compositions, which form the composition into bioplastic articles and products.

[0091] The skilled person is also able to select the appropriate conditions needed to form such articles or products.

[0092] The disclosed compositions and methods can be further understood through the following numbered paragraphs.

[0093] Paragraph 1. A biodegradable composition comprising: at least one polyhydroxyalkanoate; and at least one additive selected from:

[0094] (i) one or more amino acids;

[0095] (ii) one or more macronutrients; and

[0096] (iii) one or more micronutrients; wherein the concentration of the at least one additive is effective to modify the degradation rate of the polyhydroxyalkanoate by microbes in a marine environment, as compared to the degradation rate of the polyhydroxyalkanoate in the absence of the at least one additive.

[0097] Paragraph 2. The biodegradable composition of paragraph 1, wherein the at least one polyhydroxyalkanoate is polyhydroxybutyrate.

[0098] Paragraph 3. The biodegradable composition of any one of paragraphs 1-2, wherein the at least one additive is effective to increase the degradation rate of the polyhydroxyalkanoate by at least about 1%, 2%, 3%, 4%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or greater, compared to the degradation rate of the polyhydroxyalkanoate in the absence of the at least one additive.

[0099] Paragraph 4. The biodegradable composition of any one of paragraphs 1-2, wherein the at least one additive is effective to increase the degradation rate of the polyhydroxyalkanoate by at least about 2 times, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times, 9 times, or 10 times, compared to the degradation rate of the polyhydroxyalkanoate in the absence of the at least one additive.

[0100] Paragraph 5. The biodegradable composition of any one of paragraphs 1-4, wherein the one or more amino acids are present in the biodegradable composition at a concentration in a range of between about 0.01% to 10% of the total mass of the biodegradable composition.

[0101] Paragraph 6. The biodegradable composition of any one of paragraphs 1-5, wherein the one or more amino acids are present in the biodegradable composition and are selected from the group consisting of phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, histidine, alanine, arginine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, proline, serine, tyrosine, and combinations thereof.

[0102] Paragraph 7. The biodegradable composition of any one of paragraphs 1-6, wherein the proteins selected from the group consisting of casein, pea protein, and combinations thereof.

[0103] Paragraph 8. The biodegradable composition of any one of paragraphs 1-7, wherein the one or more macronutrients are selected from the group consisting of ammonium sulfate, sodium phosphate, potassium phosphate, ammonium chloride, and combinations thereof.

[0104] Paragraph 9. The biodegradable composition of any one of paragraphs 1-8, wherein the one or more macronutrients are present in the biodegradable composition at a concentration in a range of between about 0.1% to 10% of the total mass of the biodegradable composition.

[0105] Paragraph 10. The biodegradable composition of any one of paragraphs 1-9, wherein the one or more micronutrients are present in the biodegradable composition and further comprise an iron or cobalt metal complexed by a chelating agent.

[0106] Paragraph 11. The biodegradable composition of paragraph 10, wherein the chelating agent is ethylenediaminetetraacetic acid (EDTA).

[0107] Paragraph 12. The biodegradable composition of any one of paragraphs 1-9, wherein the one or more micronutrients comprise a vitamin.

[0108] Paragraph 13. The biodegradable composition of paragraph 12, wherein the vitamin is cobalamin or thiamine. Paragraph 14. The biodegradable composition of any one of paragraphs 1-13, wherein the one or more micronutrients are present in the biodegradable composition at a concentration in a range of between about 0.01 % to 10% of the total mass of the biodegradable composition.

[0109] Paragraph 15. The biodegradable composition of any one of paragraphs 1-14, wherein the at least one additive has a concentration of up to about 10% of the total mass of the biodegradable composition.

[0110] Paragraph 16. The biodegradable composition of any one of paragraphs 1-15, wherein the degradation rate of the polyhydroxyalkanoate is increased by at least about 10% greater, as compared to the degradation rate of the polyhydroxyalkanoate in the absence of the at least one additive.

[0111] Paragraph 17. The biodegradable composition of paragraph 1, wherein the degradation rate of the polyhydroxyalkanoate is increased from between about 1% to 100%, compared to the degradation rate of the polyhydroxyalkanoate in the absence of the at least one additive.

[0112] Paragraph 18. The biodegradable composition of paragraph 1, where the degradation rate of the polyhydroxyalkanoate is decreased by at least about 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or greater, compared to the degradation rate of the polyhydroxyalkanoate in the absence of the at least one additive.

[0113] Paragraph 19. The biodegradable composition of paragraph 1, wherein the degradation rate of the polyhydroxyalkanoate is decreased from between about 1% to 100%, as compared to the degradation rate of the polyhydroxyalkanoate in the absence of the at least one additive.

[0114] Paragraph 20. The biodegradable composition of paragraph 2, wherein the polyhydroxybutyrate is poly-3-hydroxybutyrate (P3HB).

[0115] Paragraph 21. The biodegradable composition of any one of paragraphs 1-20, wherein the at least one additive comprises at least two selections from (i)-(iii).

[0116] Paragraph 22. The biodegradable composition of any one of paragraphs 1-21, wherein the at least one additive comprises (i), (ii), and (iii).

[0117] Paragraph 23. The biodegradable composition of any one of paragraphs 1-22, wherein the microbes are marine microbes.

[0118] Paragraph 24. An article formed from the biodegradable composition of any one of paragraphs 1-23.

[0119] Paragraph 25. A method of forming an article comprising the steps of: extruding, casting, printing, rotomolding, blow molding, and / or injection molding the biodegradable composition of any one of paragraphs 1-23 to form an article.

[0120] Paragraph 26. The method of paragraph 25, wherein printing comprises 3D printing. Examples

[0121] Example 1 : Biodegradable Compositions

[0122] Materials and Methods’.

[0123] Semi-closed System Respirometry:

[0124] The biopolymer poly-3-hydroxybutyrate (PHB) is made up of carbon, which can be used by microorganisms in seawater as a source of energy. When microorganisms make use of this polymer, they are able to grow and expand their colonies. As they grow, they deplete the oxygen in their environment and respire carbon dioxide as a part of microbial respiration.

[0125] The Micro-OxyMax respirometer (Columbus Instruments) is a semi-closed system which contains 20 individual 100 mL glass bottles. Natural seawater for this study was collected from a flowing seawater system on the University of California Santa Barbara campus, which collects seawater a third of a mile offshore and 17 m deep off of Campus Point.

[0126] To form a compounded PHB biopolymer, pure PHB was compounded / blended with additives, as listed in the Sample Formulas in Table 1 below. Briefly, 50g of PHB was mixed with a given amount of additive or combination of additives. The total concentration of the additive or additives added is listed in Table 1.

[0127] For degradation testing, the compounded PHB biopolymer with additives began as pellets 3-5 mm in size. The PHB pellets were ground into a powder and sieved to select for particles of between 500-600 pm in size. 20 mg of each sample was weighed and ultraviolet (UV) sterilized for 10 minutes. 60 mL of natural seawater was added to each bottle. Negative controls only contained the seawater, while the test bottles contained 60 mL of natural seawater and 20 mg of the biopolymer. A headspace was provided inside each bottle in which the changes in oxygen and carbon dioxide concentrations were measured by the respirometer.

[0128] The bottles were placed on an orbital shaker set to about 170 rpm to ensure that the gas in the seawater did not remain in the seawater and was able to rise into the headspace to be measured. The respirometer refreshed the system with filtered atmospheric air from the surrounding room every five hours, and this allowed for this study to continue for as long as needed without becoming anoxic. The bottles were contained within a temperature-controlled incubator set to 17 °C. The study had a duration of between 19-25 days.

[0129] The aforementioned conditions are similar to those used in ASTM biodegradability testing, except that the conditions of this example were run at colder temperatures, to more closely align with the conditions in the ocean and similar marine environments. Table 1 below provides a summary of one or more additives which were used to enhance the degradation rate of PHB, when the additive was blended with PHB. For each Formula listed in Table 1 , the concentration of the total additives (i.e. all of the additives) blended with PHB was in the range of about 0.8 to about 5.5% wt / wt. “N” denotes nitrogen and “P” denotes phosphorus. Ammonium chloride was used as the nitrogen source. Sodium phosphate was used as the phosphorus source. “Fe” denotes iron, where Fe-EDTA served as the source.

[0130] Table 1. Sample Formulas and Additives Tested

[0131] Results and Discussion:

[0132] Figure 1 shows the fold-enhancement in biodegradation of the sample formulas listed in Table 1 above, relative to a standard injection-molding grade polyhydroxybutyrate (PHB), where values greater than 1 indicated an enhancement in biodegradation rate. Biodegradation was assessed using carbon dioxide-based respirometry, as described above. Polybutylene succinate (PBS) and poly(lactic acid) (PLA), which are two other commercially available biopolymers, were also evaluated. As shown in the graph, the presence of additives can increase the degradation rate of the PHB in the samples by up to 2,2-fold, when exposed to microbes in the seawater.

[0133] Figure 2 shows a representative carbon dioxide accumulation curve (averaged replicates) for Sample Formula 116 generated during respirometry, which were used to calculate the biodegradation enhancements shown in Figure 1. The natural biopolymer, chitin, was used as a positive control (data not shown in Figure 2). “IM” refers to a standard injection molding blend of polyhydroxybutyrate obtained from Mango Materials in the form of pellets 3-5 mm in size which were ground into a powder and sieved to select for particles of between 500-600 pm in size. The chitin control was used to validate the experimental setup as it is known to be biodegradable in seawater and is the suggested positive control for the ASTM marine biodegradability standard.

[0134] More specifically, respirometry allowed for the calculation of the number of moles of carbon dioxide produced in each sample formula tested, where it was assumed that all the carbon dioxide originated from the PHB respired by microbes in the seawater. The amount of PHB respired for each sample formula was compared and then normalized to the amount of carbon dioxide respired in a concurrent incubation with the standard injection-molding grade PHB (denoted IM).

[0135] Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of skill in the art to which the disclosed invention belongs. Publications cited herein and the materials for which they are cited are specifically incorporated by reference.

[0136] Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following claims.

Claims

CLAIMSWe claim:

1. A biodegradable composition comprising: at least one polyhydroxyalkanoate; and at least one additive selected from:(i) one or more amino acids;(ii) one or more macronutrients; and(iii) one or more micronutrients; wherein the concentration of the at least one additive is effective to modify the degradation rate of the polyhydroxyalkanoate by microbes in a marine environment, as compared to the degradation rate of the polyhydroxyalkanoate in the absence of the at least one additive.

2. The biodegradable composition of claim 1 , wherein the at least one polyhydroxyalkanoate is polyhydroxybutyrate.

3. The biodegradable composition of claim 1 , wherein the at least one additive is effective to increase the degradation rate of the polyhydroxy alkanoate by at least about 1%, 2%, 3%, 4%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or greater, compared to the degradation rate of the polyhydroxy alkanoate in the absence of the at least one additive.

4. The biodegradable composition of claim 1 , wherein the at least one additive is effective to increase the degradation rate of the polyhydroxyalkanoate by at least about 2 times, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times, 9 times, or 10 times, compared to the degradation rate of the polyhydroxyalkanoate in the absence of the at least one additive.

5. The biodegradable composition of claim 1 , wherein the one or more amino acids are present in the biodegradable composition at a concentration in a range of between about 0.01% to 10% of the total mass of the biodegradable composition.

6. The biodegradable composition of claim 1 , wherein the one or more amino acids are present in the biodegradable composition and are selected from the group consisting of phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, histidine, alanine, arginine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, proline, serine, tyrosine, and combinations thereof.

7. The biodegradable composition of claim 1 , wherein the proteins selected from the group consisting of casein, pea protein, and combinations thereof.

8. The biodegradable composition of claim 1 , wherein the one or more macronutrients are selected from the group consisting of ammonium sulfate, sodium phosphate, potassium phosphate, ammonium chloride, and combinations thereof.

9. The biodegradable composition of claim 1 , wherein the one or more macronutrients are present in the biodegradable composition at a concentration in a range of between about 0. 1 % to 10% of the total mass of the biodegradable composition.

10. The biodegradable composition of claim 1 , wherein the one or more micronutrients are present in the biodegradable composition and further comprise an iron or cobalt metal complexed by a chelating agent.

11. The biodegradable composition of claim 10, wherein the chelating agent is ethylenediaminetetraacetic acid (EDTA).

12. The biodegradable composition of claim 1 , wherein the one or more micronutrients comprise a vitamin.

13. The biodegradable composition of claim 12, wherein the vitamin is cobalamin or thiamine.

14. The biodegradable composition of claim 1 , wherein the one or more micronutrients are present in the biodegradable composition at a concentration in a range of between about 0.01% to 10% of the total mass of the biodegradable composition.

15. The biodegradable composition of claim 1 , wherein the at least one additive has a concentration of up to about 10% of the total mass of the biodegradable composition.

16. The biodegradable composition of claim 1 , wherein the degradation rate of the polyhydroxyalkanoate is increased by at least about 10% greater, as compared to the degradation rate of the polyhydroxyalkanoate in the absence of the at least one additive.

17. The biodegradable composition of claim 1 , wherein the degradation rate of the polyhydroxyalkanoate is increased from between about 1% to 100%, compared to the degradation rate of the polyhydroxyalkanoate in the absence of the at least one additive.

18. The biodegradable composition of claim 1 , where the degradation rate of the polyhydroxyalkanoate is decreased by at least about 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or greater, compared to the degradation rate of the polyhydroxyalkanoate in the absence of the at least one additive.

19. The biodegradable composition of claim 1 , wherein the degradation rate of the polyhydroxyalkanoate is decreased from between about 1% to 100%, as compared to the degradation rate of the polyhydroxyalkanoate in the absence of the at least one additive.

20. The biodegradable composition of claim 2, wherein the polyhydroxybutyrate is poly-3- hydroxybutyrate (P3HB).

21. The biodegradable composition of claim 1 , wherein the at least one additive comprises at least two selections from (i)-(iii).

22. The biodegradable composition of claim 1 , wherein the at least one additive comprises (i), (ii), and (iii).

23. The biodegradable composition of claim 1 , wherein the microbes are marine microbes.

24. An article formed from the biodegradable composition of any one of claims 1-23.

25. A method of forming an article comprising the steps of: extruding, casting, printing, rotomolding, blow molding, and / or injection molding the biodegradable composition of any one of claims 1-23 to form an article.

26. The method of claim 25, wherein printing comprises 3D printing.

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