Polyhydroxyalkanoate additives

Further examples of natural polymers also include collagen, chitosan, and polyhydroxyalkanoates. Additional synthetic polymers include poly(glycolic acid) (PGA), poly(lactic acid) (PLA), copolymers of PGA and PLA, and polydioxananone. 

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). 

An additional advantage of the polyhydroxyalkanoates is that the polymers can be produced by fermentation. Certain types of bacteria produce PHAs for energy storage when they are grown in glucose solution in the absence of specific nutrients. The polymer forms as discrete granules within the bacterial cell, and it is then removed by extraction to give a white powder that can be melted and modified into a variety of different products. 

Special types of purpose-built polymers can also be made with the intention of enabling more rapid direct microbiological attack and decomposition of these materials. Classes of both condensation and addition polymers among the polyesters, vinylic polymers, and polyhydroxyalkanoates typify current candidate materials being tested in these applications (e.g., Eq. 23.9), but as yet high costs have discouraged large scale exploitation. 

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. 

Abstract The most important aspect of any feedstock for industrial-scale production of polyhydroxyalkanoate (PHA) is market stability. One would expect the feedstock to be sustainable in terms of supply, cost and quahty. In addition, recently, there is also growing concerns over the use of food-grade feedstock for making nonedible products such as fuel and material. Therefore, the selection of a feedstock for PHA production must take into consideration the effect on global food supply. This chapter presents the current scenario of the palm oil industry along with issues such as land management and conservation of biodiversity. In order to ensure the sustainability of PHA production from palm oil, several strategies are proposed. 

Abstract Polyhydroxyalkanoate (PHA) is an attractive material because it can be produced from renewable resources and because of its plastic-like properties. In addition, PHA can be degraded by the action of microbial enzymes. Although PHA resanbles some commodity plastics, the performance and cost of PHA are not yet good enough for widespread applications as plastic materials. Therefore, the PHA commercialization attempts by many industries for bulk applications have been challenging. However, PHA also possesses interesting properties that can be developed for non-plastic applications. This chapter describes some new niche applications for PHA in cosmetics and wastewater treatment. 

Abstract Polyhydroxyalkanoate (PHA) initially received serious attention as a possible substitute for petrochemical-based plastics because of the anticipated shortage in the supply of petroleum. Since then, PHA has remained as an interesting material to both the academia and indusby. Now, we know more about this microbial storage polyester and have developed efficient fermentation systems for the large-scale production of PHA. Besides sugars, plant oils will become one of the important feedstock for the industrial-scale production of PHA. In addition, PHA will find new apphcations in various areas. This chapter summarizes the future prospects and the importance of developing a sustainable production system for PHA. 

The book addresses the most important biopolymer classes like polysaccharides, lignin, proteins and polyhydroxyalkanoates as raw materials for bio-based plastics, as well as materials derived from bio-based monomers like lipids, poly(lactic acid), polyesters, polyamides and polyolefines. Additional chapters on general topics - the market and availability of renewable raw materials, the importance of bio-based content and the issue of biodegradability - will provide important information related to all bio-based polymer classes. 

In addition to bio-based polyesters such as poly(lactic acid) (PLA), polyhydroxyalkanoates (PHAs), and poly(ethylene furanoate) (PEE), all based upon biomass-derived building blocks that have a structure different from today s commercial petrochemical-based polyesters, biobased polyesters can be developed having an identical structure to well-known petrochemical based polyesters. A very important class of such drop-in type bio-based polyesters are represented by polyesters based upon either isophthalic acid or terephthalic acid, such as PET,... 

Polyhydroxyalkanoate(s) (PHA) have gained rapid interest worldwide. The structural diversity of hydroxyalkanoates has resulted in materials with a wide range of physical and thermal characteristics. In addition, the variety of characteristics are significantly impacted by every aspect of upstream processing, as well as recovery during downstream processing. The diversity and versatility of PHA have opened up various opportunities for exploitation as many possibilities are yet to be discovered and evaluated in various applications. 

The PHAs, PHB is the most extensively characterized polymer, mainly because it was the first to be discovered. The diversity of bacterial PHAs has changed dramatically. Until 1970 s, 3HB was considered as the only constituent of PHAs. hi 1980 s, PHAs having other monomers besides 3HB were shown to be accumulated by many bacteria with addition of certain precursors in the production medium. Figure 2 shows widely studied polyhydroxyalkanoates, which are PHB, PHV, and copolymer of PHB-co-PHV Today more than 150 different monomers of PHAs are synthesized by different microorganisms which include the following ... 

The starch-based polymers iiKlnde aritylose, lydroxyl-propylated starch and dextrin, polylactides (PLA), polyhydroxyalkanoate (PHA), polyhydroxybnterate (PHB), and a copolymer PHB and valeric acids (PHBAO- In addition, biodegradable films can also be formed from chitosan, which is derived finm the chitin of crastacean and insect... 

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