Polyhydroxyalkanoates

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Structure of poly-(R)-3-hydroxybutyrate (P3HB), a polyhydroxyalkanoate Poly-(R)-3-hydroxybutyrat.svg
Structure of poly-(R)-3-hydroxybutyrate (P3HB), a polyhydroxyalkanoate
Chemical structures of P3HB, PHV and their copolymer PHBV Polyhydroxyalkanoates.png
Chemical structures of P3HB, PHV and their copolymer PHBV

Polyhydroxyalkanoates or PHAs are polyesters produced in nature by numerous microorganisms, including through bacterial fermentation of sugars or lipids. [1] When produced by bacteria they serve as both a source of energy and as a carbon store. More than 150 different monomers can be combined within this family to give materials with extremely different properties. [2] These plastics are biodegradable and are used in the production of bioplastics. [3]

Contents

They can be either thermoplastic or elastomeric materials,[ citation needed ] with melting points ranging from 40 to 180 °C.[ citation needed ]

The mechanical properties and biocompatibility of PHA can also be changed by blending, modifying the surface or combining PHA with other polymers, enzymes and inorganic materials, making it possible for a wider range of applications. [4]

Biosynthesis

Certain strains of Bacillus subtilis bacteria can be used to produce polyhydroxyalkanoates Bacillus subtilis Gram.jpg
Certain strains of Bacillus subtilis bacteria can be used to produce polyhydroxyalkanoates

To induce PHA production in a laboratory setting, a culture of a micro-organism such as Cupriavidus necator can be placed in a suitable medium and fed appropriate nutrients so that it multiplies rapidly. Once the population has reached a substantial level, the nutrient composition can be changed to force the micro-organism to synthesize PHA. The yield of PHA obtained from the intracellular granule inclusions can be as high as 80% of the organism's dry weight.[ citation needed ]

The biosynthesis of PHA is usually caused by certain deficiency conditions (e.g. lack of macro elements such as phosphorus, nitrogen, trace elements, or lack of oxygen) and the excess supply of carbon sources. [5] However, the prevalence of PHA production within either a mono-culture or a set of mixed-microbial organisms can also simply be dependent on overall nutrient limitation, not just macro elements. This is especially the case in the 'feast/famine' cycle method for induction of PHA production, wherein carbon is periodically added and depleted to cause famine, which encourages cells to produce PHA during 'feast' as a storage method for periods of famine. [ citation needed ]

Polyesters are deposited in the form of highly refractive granules in the cells. Depending upon the microorganism and the cultivation conditions, homo- or copolyesters with different hydroxyalkanoic acids are generated. PHA granules are then recovered by disrupting the cells. [6] Recombinant Bacillus subtilis str. pBE2C1 and Bacillus subtilis str. pBE2C1AB were used in production of polyhydroxyalkanoates (PHA) and it was shown that they could use malt waste as carbon source for lower cost of PHA production.

PHA synthases are the key enzymes of PHA biosynthesis. They use the coenzyme A - thioester of (r)-hydroxy fatty acids as substrates. The two classes of PHA synthases differ in the specific use of hydroxy fatty acids of short or medium chain length.

The resulting PHA is of the two types:

A few bacteria, including Aeromonas hydrophila and Thiococcus pfennigii , synthesize copolyester from the above two types of hydroxy fatty acids, or at least possess enzymes that are capable of part of this synthesis.

Another even larger scale synthesis can be done with the help of soil organisms. For lack of nitrogen and phosphorus they produce a kilogram of PHA per three kilograms of sugar.

The simplest and most commonly occurring form of PHA is the fermentative production of poly-beta-hydroxybutyrate [poly(3-hydroxybutyrate), P(3HB)], which consists of 1000 to 30000 hydroxy fatty acid monomers.

Industrial production

In the industrial production of PHA, the polyester is extracted and purified from the bacteria by optimizing the conditions of microbial fermentation of sugar, glucose, or vegetable oil.

In the 1980s, Imperial Chemical Industries developed poly(3-hydroxybutyrate-co-3-hydroxyvalerate) obtained via fermentation that was named "Biopol". It was sold under the name "Biopol" and distributed in the U.S. by Monsanto and later Metabolix. [7]

As raw material for the fermentation, carbohydrates such as glucose and sucrose can be used, but also vegetable oil or glycerine from biodiesel production. Researchers in industry are working on methods with which transgenic crops will be developed that express PHA synthesis routes from bacteria and so produce PHA as energy storage in their tissues. Several companies are working to develop methods of producing PHA from waste water, including Veolia subsidiary Anoxkaldnes. [8] and start-ups, Micromidas, [9] Mango Materials, [10] [11] Full Cycle Bioplastics, [12] Newlight and Paques Biomaterials. [13] [14]

PHAs are processed mainly via injection molding, extrusion and extrusion bubbles into films and hollow bodies.

Material properties

PHA polymers are thermoplastic, can be processed on conventional processing equipment, and are, depending on their composition, ductile and more or less elastic. [15] They differ in their properties according to their chemical composition (homo-or copolyester, contained hydroxy fatty acids).

They are UV stable, in contrast to other bioplastics from polymers such as polylactic acid, partial ca. temperatures up to 180 °C, and show a low permeation of water. The crystallinity can lie in the range of a few to 70%. Processability, impact strength and flexibility improves with a higher percentage of valerate in the material. PHAs are soluble in halogenated solvents such chloroform, dichloromethane or dichloroethane. [16]

PHB is similar in its material properties to polypropylene (PP), has a good resistance to moisture and aroma barrier properties. Polyhydroxybutyric acid synthesized from pure PHB is relatively brittle and stiff. PHB copolymers, which may include other fatty acids such as beta-hydroxyvaleric acid, may be elastic.

Applications

Due to its biodegradability and potential to create bioplastics with novel properties, much interest exists to develop the use of PHA-based materials. PHA fits into the green economy as a means to create plastics from non-fossil fuel sources. Furthermore, active research is being carried out for the biotransformation "upcycling" of plastic waste (e.g., polyethylene terephthalate and polyurethane) into PHA using Pseudomonas putida bacteria. [17]

A PHA copolymer called PHBV (poly(3-hydroxybutyrate-co-3-hydroxyvalerate)) is less stiff and tougher, and it may be used as packaging material.

In June 2005, US company Metabolix, Inc. received the US Presidential Green Chemistry Challenge Award (small business category) for their development and commercialisation of a cost-effective method for manufacturing PHAs. [18]

There are potential applications for PHA produced by micro-organisms [2] within the agricultural, [19] medical and pharmaceutical industries, primarily due to their biodegradability.

Fixation and orthopaedic applications have included sutures, suture fasteners, meniscus repair devices, rivets, tacks, staples, screws (including interference screws), bone plates and bone plating systems, surgical mesh, repair patches, slings, cardiovascular patches, orthopedic pins (including bone.lling augmentation material), adhesion barriers, stents, guided tissue repair/regeneration devices, articular cartilage repair devices, nerve guides, tendon repair devices, atrial septal defect repair devices, pericardial patches, bulking and filling agents, vein valves, bone marrow scaffolds, meniscus regeneration devices, ligament and tendon grafts, ocular cell implants, spinal fusion cages, skin substitutes, dural substitutes, bone graft substitutes, bone dowels, wound dressings, and hemostats. [20]

Related Research Articles

<span class="mw-page-title-main">Biopolymer</span> Polymer produced by a living organism

Biopolymers are natural polymers produced by the cells of living organisms. Like other polymers, biopolymers consist of monomeric units that are covalently bonded in chains to form larger molecules. There are three main classes of biopolymers, classified according to the monomers used and the structure of the biopolymer formed: polynucleotides, polypeptides, and polysaccharides. The Polynucleotides, RNA and DNA, are long polymers of nucleotides. Polypeptides include proteins and shorter polymers of amino acids; some major examples include collagen, actin, and fibrin. Polysaccharides are linear or branched chains of sugar carbohydrates; examples include starch, cellulose, and alginate. Other examples of biopolymers include natural rubbers, suberin and lignin, cutin and cutan, melanin, and polyhydroxyalkanoates (PHAs).

Ingeo is the trademarked brand name for a range of polylactic acid (PLA) biopolymers owned by NatureWorks.

<span class="mw-page-title-main">Polyhydroxybutyrate</span> Polymer

Polyhydroxybutyrate (PHB) is a polyhydroxyalkanoate (PHA), a polymer belonging to the polyesters class that are of interest as bio-derived and biodegradable plastics. The poly-3-hydroxybutyrate (P3HB) form of PHB is probably the most common type of polyhydroxyalkanoate, but other polymers of this class are produced by a variety of organisms: these include poly-4-hydroxybutyrate (P4HB), polyhydroxyvalerate (PHV), polyhydroxyhexanoate (PHH), polyhydroxyoctanoate (PHO) and their copolymers.

<span class="mw-page-title-main">PLGA</span> Copolymer of varying ratios of polylactic acid and polyglycolic acid

PLGA, PLG, or poly(lactic-co-glycolic acid) is a copolymer which is used in a host of Food and Drug Administration (FDA) approved therapeutic devices, owing to its biodegradability and biocompatibility. PLGA is synthesized by means of ring-opening co-polymerization of two different monomers, the cyclic dimers (1,4-dioxane-2,5-diones) of glycolic acid and lactic acid. Polymers can be synthesized as either random or block copolymers thereby imparting additional polymer properties. Common catalysts used in the preparation of this polymer include tin(II) 2-ethylhexanoate, tin(II) alkoxides, or aluminum isopropoxide. During polymerization, successive monomeric units are linked together in PLGA by ester linkages, thus yielding a linear, aliphatic polyester as a product.

<span class="mw-page-title-main">Polylactic acid</span> Biodegradable polymer

Polylactic acid, also known as poly(lactic acid) or polylactide (PLA), is a thermoplastic polyester with backbone formula (C
3H
4O
2)
n or [–C(CH
3)HC(=O)O–]
n, formally obtained by condensation of lactic acid C(CH
3)(OH)HCOOH with loss of water. It can also be prepared by ring-opening polymerization of lactide [–C(CH
3)HC(=O)O–]
2, the cyclic dimer of the basic repeating unit.

<span class="mw-page-title-main">Bioplastic</span> Plastics derived from renewable biomass sources

Bioplastics are plastic materials produced from renewable biomass sources, such as vegetable fats and oils, corn starch, straw, woodchips, sawdust, recycled food waste, etc. Some bioplastics are obtained by processing directly from natural biopolymers including polysaccharides and proteins, while others are chemically synthesised from sugar derivatives and lipids from either plants or animals, or biologically generated by fermentation of sugars or lipids. In contrast, common plastics, such as fossil-fuel plastics are derived from petroleum or natural gas.

β-Hydroxybutyric acid Chemical compound

β-Hydroxybutyric acid, also known as 3-hydroxybutyric acid or BHB, is an organic compound and a beta hydroxy acid with the chemical formula CH3CH(OH)CH2CO2H; its conjugate base is β-hydroxybutyrate, also known as 3-hydroxybutyrate. β-Hydroxybutyric acid is a chiral compound with two enantiomers: D-β-hydroxybutyric acid and L-β-hydroxybutyric acid. Its oxidized and polymeric derivatives occur widely in nature. In humans, D-β-hydroxybutyric acid is one of two primary endogenous agonists of hydroxycarboxylic acid receptor 2 (HCA2), a Gi/o-coupled G protein-coupled receptor (GPCR).

<span class="mw-page-title-main">Biodegradable plastic</span> Plastics that can be decomposed by the action of living organisms

Biodegradable plastics are plastics that can be decomposed by the action of living organisms, usually microbes, into water, carbon dioxide, and biomass. Biodegradable plastics are commonly produced with renewable raw materials, micro-organisms, petrochemicals, or combinations of all three.

Paucimonas lemoignei, formerly [Pseudomonas lemoignei], is a Gram-negative soil bacterium. It is aerobic, motile, and rod-shaped.

PBAT is a biodegradable random copolymer, specifically a copolyester of adipic acid, 1,4-butanediol and terephthalic acid. PBAT is produced by many different manufacturers and may be known by the brand names ecoflex, Wango,Ecoworld, Eastar Bio, and Origo-Bi. It is also called poly(butylene adipate-co-terephthalate) and sometimes polybutyrate-adipate-terephthalate or even just "polybutyrate". It is generally marketed as a fully biodegradable alternative to low-density polyethylene, having many similar properties including flexibility and resilience, allowing it to be used for many similar uses such as plastic bags and wraps. It is depicted as a block co-polymer here due to the common synthetic method of first synthesizing two copolymer blocks and then combining them. However, it is important to note that the actual structure of the polymer is a random co-polymer of the blocks shown.

Biodegradable polymers are a special class of polymer that breaks down after its intended purpose by bacterial decomposition process to result in natural byproducts such as gases (CO2, N2), water, biomass, and inorganic salts. These polymers are found both naturally and synthetically made, and largely consist of ester, amide, and ether functional groups. Their properties and breakdown mechanism are determined by their exact structure. These polymers are often synthesized by condensation reactions, ring opening polymerization, and metal catalysts. There are vast examples and applications of biodegradable polymers.

Poly(3-hydroxybutyrate) depolymerase (EC 3.1.1.75, PHB depolymerase, systematic name poly[(R)-3-hydroxybutanoate] hydrolase) is an enzyme used in the degradation processes of a natural polyester poly(3-hydroxyburate). This enzyme has growing commercialization interests due to it implications in biodegradable plastic decomposition.

<span class="mw-page-title-main">PHBV</span> Chemical compound

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate), commonly known as PHBV, is a polyhydroxyalkanoate-type polymer. It is biodegradable, nontoxic, biocompatible plastic produced naturally by bacteria and a good alternative for many non-biodegradable synthetic polymers. It is a thermoplastic linear aliphatic polyester. It is obtained by the copolymerization of 3-hydroxybutanoic acid and 3-hydroxypentanoic acid. PHBV is used in speciality packaging, orthopedic devices and in controlled release of drugs. PHBV undergoes bacterial degradation in the environment.

Rhodovulum sulfidophilum is a gram-negative purple nonsulfur bacteria. The cells are rod-shaped, and range in size from 0.6 to 0.9 μm wide and 0.9 to 2.0 μm long, and have a polar flagella. These cells reproduce asexually by binary fission. This bacterium can grow anaerobically when light is present, or aerobically (chemoheterotrophic) under dark conditions. It contains the photosynthetic pigments bacteriochlorophyll a and of carotenoids.

<span class="mw-page-title-main">Synthetic microbial consortia</span>

Synthetic microbial consortia are multi-population systems that can contain a diverse range of microbial species, and are adjustable to serve a variety of industrial, ecological, and tautological interests. For synthetic biology, consortia take the ability to engineer novel cell behaviors to a population level.

β-Butyrolactone Chemical compound

β-Butyrolactone is the intramolecular carboxylic acid ester (lactone) of the optically active 3-hydroxybutanoic acid. It is produced during chemical synthesis as a racemate. β-Butyrolactone is suitable as a monomer for the production of the biodegradable polyhydroxyalkanoate poly(3-hydroxybutyrate) (PHB). Polymerisation of racemic (RS)-β-butyrolactone provides (RS)-polyhydroxybutyric acid, which, however, is inferior in essential properties (e.g. strength or degradation behaviour) to the (R)-poly-3-hydroxybutyrate originating from natural sources.

Ipsita Roy is a British-Indian materials scientist who is a professor at the University of Sheffield. Her research considers natural polymers of bacterial origin for medical applications. She was elected to the New York Academy of Sciences in 1997 and serves as the Editor of the Journal of Chemical Technology & Biotechnology.

<span class="mw-page-title-main">Amar K. Mohanty</span> Material scientist and biomaterial engineer

Amar K. Mohanty is a material scientist and biobased material engineer, academic and author. He is a Professor and Distinguished Research Chair in Sustainable Biomaterials at the Ontario Agriculture College and is the Director of the Bioproducts Discovery and Development Centre at the University of Guelph.

<span class="mw-page-title-main">Plastic degradation by marine bacteria</span> Ability of bacteria to break down plastic polymers

Plastic degradation in marine bacteria describes when certain pelagic bacteria break down polymers and use them as a primary source of carbon for energy. Polymers such as polyethylene(PE), polypropylene (PP), and polyethylene terephthalate (PET) are incredibly useful for their durability and relatively low cost of production, however it is their persistence and difficulty to be properly disposed of that is leading to pollution of the environment and disruption of natural processes. It is estimated that each year there are 9-14 million metric tons of plastic that are entering the ocean due to inefficient solutions for their disposal. The biochemical pathways that allow for certain microbes to break down these polymers into less harmful byproducts has been a topic of study to develop a suitable anti-pollutant.

An oleaginous microorganism is a type of microbe that accumulates lipid as a normal part of its metabolism. Oleaginous microbes may accumulate an array of different lipid compounds, including polyhydroxyalkanoates, triacylglycerols, and wax esters. Various microorganisms, including bacteria, fungi, and yeast, are known to accumulate lipids. These organisms are often researched for their potential use in producing fuels from waste products.

References

  1. ↑ Lu, Jingnan; Tappel, Ryan C.; Nomura, Christopher T. (2009-08-05). "Mini-Review: Biosynthesis of Poly(hydroxyalkanoates)". Polymer Reviews. 49 (3): 226–248. doi:10.1080/15583720903048243. ISSN   1558-3724. S2CID   96937618.
  2. 1 2 Doi, Yoshiharu; Steinbuchel, Alexander (2002). Biopolymers. Weinheim, Germany: Wiley-VCH. ISBN   978-3-527-30225-3.[ page needed ]
  3. ↑ Bhubalan, Kesaven; Lee, Wing-Hin; Sudesh, Kumar (2011-05-03), Domb, Abraham J.; Kumar, Neeraj; Ezra, Aviva (eds.), "Polyhydroxyalkanoate", Biodegradable Polymers in Clinical Use and Clinical Development, John Wiley & Sons, Inc., pp. 247–315, doi:10.1002/9781118015810.ch8, ISBN   978-1-118-01581-0
  4. ↑ Michael, Anne John (September 12, 2004). "Polyhydroxyalkanoates for tissue engineering". Archived from the original on January 28, 2007.
  5. ↑ Kim, Y. B.; Lenz, R. W. (2001). "Polyesters from microorganisms". Advances in Biochemical Engineering/Biotechnology. 71: 51–79. doi:10.1007/3-540-40021-4_2. ISBN   978-3-540-41141-3. ISSN   0724-6145. PMID   11217417.
  6. ↑ Jacquel, Nicolas; Lo, Chi-Wei; Wei, Yu-Hong; Wu, Ho-Shing; Wang, Shaw S. (2008). "Isolation and purification of bacterial poly(3-hydroxyalkanoates)". Biochemical Engineering Journal. 39 (1): 15–27. doi:10.1016/j.bej.2007.11.029.
  7. ↑ Ewa Rudnik (3 January 2008). Compostable Polymer Materials. Elsevier. p. 21. ISBN   978-0-08-045371-2 . Retrieved 10 July 2012.
  8. ↑ Seb Egerton-Read (September 9, 2015). "A New Way to Make Plastic". Circulate. Retrieved October 23, 2015.
  9. ↑ Martin Lamonica (May 27, 2010). "Micromidas to test sludge-to-plastic tech". CNET . Retrieved October 23, 2015.
  10. ↑ Mango Materials selected for Phase II STTR NASA award (10. Aug 2017) BioplasticsMagazine.com
  11. ↑ How Close Are We to Reinventing Plastic? (Dec 18, 2019) Seeker
  12. ↑ "Full Cycle Bioplastics Turns Bacteria Waste into "Nature's Plastic"". 11 July 2019.
  13. ↑ "Paques biomaterials website".
  14. ↑ Provincie Drenthe (2022). "Paques Biomaterials investeert 58 miljoen in demo-installatie en fabriek in Emmen".
  15. ↑ Cataldi, P. (July 2020). "Multifunctional Biocomposites Based on Polyhydroxyalkanoate and Graphene/Carbon Nanofiber Hybrids for Electrical and Thermal Applications". ACS Applied Polymer Materials. 2 (8): 3525–3534. arXiv: 2005.08525 . doi:10.1021/acsapm.0c00539. S2CID   218673849.
  16. ↑ Jacquel, Nicolas; Lo, Chi-Wei; Wu, Ho-Shing; Wei, Yu-Hong; Wang, Shaw S. (2007). "Solubility of polyhydroxyalkanoates by experiment and thermodynamic correlations". AIChE Journal. 53 (10): 2704–14. doi: 10.1002/aic.11274 .
  17. ↑ "Homepage - P4SB". www.p4sb.eu. Retrieved 2017-10-26.
  18. ↑ "The Presidential Green Chemistry Challenge Awards Program" (PDF). The Presidential Green Chemistry Challenge Awards Program: Summary of 2005 Award Entries and Recipients. Environmental Protection Agency: 8. 2005. Archived from the original (PDF) on 2012-07-08.
  19. ↑ Amelia, Tan Suet May; Govindasamy, Sharumathiy; Tamothran, Arularasu Muthaliar; Vigneswari, Sevakumaran; Bhubalan, Kesaven (2019), Kalia, Vipin Chandra (ed.), "Applications of PHA in Agriculture", Biotechnological Applications of Polyhydroxyalkanoates, Springer Singapore, pp. 347–361, doi:10.1007/978-981-13-3759-8_13, ISBN   978-981-13-3758-1, S2CID   139827723
  20. ↑ Chen, Guo-Qiang; Wu, Qiong (2005). "The application of polyhydroxyalkanoates as tissue engineering materials". Biomaterials. 26 (33): 6565–78. doi:10.1016/j.biomaterials.2005.04.036. PMID   15946738.

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