Biodegradable polyhydroxyalkanoates PHAs

Metabolix Inc. (USA) has developed a fermentation process to produce biodegradable polyhydroxyalkanoate (PHA) from renewable feedstock by incorporating genes from PHA-producing bacteria into a strain of Escherichia coli. The fermentation process... 

Other blends such as polyhydroxyalkanoates (PHA) with cellulose acetate (208), PHA with polycaprolactone (209), poly(lactic acid) with poly(ethylene glycol) (210), chitosan and cellulose (211), poly(lactic acid) with inorganic fillers (212), and PHA and aUphatic polyesters with inorganics (213) are receiving attention. The different blending compositions seem to be limited only by the number of polymers available and the compatibiUty of the components. The latter blends, with all natural or biodegradable components, appear to afford the best approach for future research as property balance and biodegradabihty is attempted. Starch and additives have been evaluated ia detail from the perspective of stmcture and compatibiUty with starch (214). 

Polyhydroxyalkanoate (PHA) is a biodegradable and biocompatible thermoplastic that can be synthesized in many microoiganisms from almost all genera of the microbial kingdom. Many microoiganisms synthesize polyhydroxyalkanoates (PHAs) as intracellular carbon and energy reserve materials [1]. These microbial polyesters materials are thermoplastics with biodegradable properties [2]. PHAs are usually accumulated... 

Polysacharides such as starch are the most prevalent naturally biodegradable polymer in commercial use. Aliphatic polyesters such as polyhydroxyalkanoates (PHA) are also a family of easily biodegradable polymers found in nature that are beginning to find commercial use. 

Biodegradable polymers that are based on renewable resources include polyesters such as polylactic acid (PLA) and polyhydroxyalkanoate (PHA). Biodegradable polymers can also be made from extracts from plants and vegetables such as corn, maize, palm oil, soya and potatoes. 

Within this context, the search for a material that is durable while in use and degradable after its disposal has led to the emergence of biodegradable plastic— materials that decompose into carbon dioxide and water as the final result of the action of microorganisms such as bacteria and fungi [5]. Polyhydroxyalkanoates (PHAs) constitute examples of such materials. 

The bacterial polyhydroxyalkanoates (PHAs) and their principal representative poly(3-R-hydroxybutyrate) (PHB) create a competitive option to conventional synthetic polymers such as polypropylene, polyethylene, polyesters et al. These polymers are nontoxic and renewable. Their biotechnology output does not depend on hydrocarbon production as well as their biodegradation intermediates and resulting products (water and carbon dioxide) do not provoke the adverse actions in environmental media or living systems [1-3]. Being enviromnent friendly [4], the PHB and its derivatives are used as the alternative packaging materials, which are biodegradable in the soil or different humid media [5, 6]. 

Abstract Polyhydroxyalkanoate (PHA) is a plastic-like material synthesized by many bacteria. PHA serves as an energy and carbon storage componnd for the bacteria. PHA can be extracted and purified from the bacterial cells and the resulting product resembles some commodity plastics such as polypropylene. Because PHA is a microbial product, there are natural enzymes that can degrade and decompose PHA. Therefore, PHA is an attractive material that can be developed as a bio-based and biodegradable plastic. In addition, PHA is also known to be biocompatible and can be used in medical devices and also as bioresorbable tissue engineering scaffolds. In this chapter, a brief introduction about PHA and the fermentation feedstock for its production are given. 

Ali N, Suhaimi NS (2009) Performance evaluation of locally fabricated asymmetric nanofiltration membrane for Batik industry effluent. World Appl Sci J 5 46-52 Alias Z, Tan IKP (2005) Isolation of palm oil-utilising, polyhydroxyalkanoate (PHA)-producing bacteria by an enrichment technique. Bioresour Technol 96 1229-1234 Allen AD, Anderson WA, Ayorinde FO, Eribo BE (2010) Biosynthesis and characterization of copolymer poly(3HB-co-3HV) from saponified Jatropha curcas oil by Pseudomonas oleovorans. J Ind Microbiol Biotechnol 37 849-856 Allen AD, Anderson WA, Ayorinde F, Eribo BE (2011) Isolation and characterization of an extracellular thermoalkanophilic P(3HB-co-3HV) depolymerase from Streptomyces sp. INI. Int Biodeterior Biodegrad 65 777-785... 

Some synthetic polymers like, polyurethanes, specifically polyether-polyurethanes, are likely to be degraded by microbes but not completely. However, several polymers such as, polyamides, polyfluorocarbons, polyethylene, polypropylene, and polycarbonate are highly resistant to microbial degradation. Natural polymers are generally more biodegradable than synthetic polymers specifically, polymers with ester groups like aliphatic polyesters [1]. Therefore, several natural polymers such as cellulose, starch, blends of those with synthetic polymers, polylactate, polyester-amide, and polyhydroxyalkanoates (PHAs) have been the focus of attention in the recent years [3]. 

Puiushothaman, M., Anderson, R., Narayana, S. and Jayaraman, V. (2001) Industrial byproducts as cheaper medium components influencing the production of polyhydroxyalkanoates (PHA) - biodegradable plastics. Bioprocess and Biosystems Engineering, 24, 131-136. 

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