Polyhydroxyalkanoates substrates

Xs = slowly biodegradable substrate XAUT = autotrophic, nitrifying biomass XpHA = stored polyhydroxyalkanoate XPA0 = phosphorus-accumulating organisms... 

Polyhydroxyalkanoate synthase (systematic name acyl-CoA 3-hydroxybutyrate 0-acyltransferase EC 2.3.1. class) is responsible for the polymerizations of PHAs in vivo because it catalyzes the stereoselective conversion of (/ )-3-hydroxyacyl-CoA substrates to PHAs with the concomitant release of CoA (see Fig. 2) [3]. 

Haywood, G.W., Anderson, A.)., and Dawes, E.A. (1989) The importance of PHB-synthase substrate specificuity in polyhydroxyalkanoate synthesis by Alcaligenes eutrophus. FEMS Microbiol. Lett., 57,1-6. 

ALB 11] Albuquerque M.G.E., Martino V., Pollet E., et al., Mixed culture polyhydroxyalkanoate (PHA) production from volatile fatty acid (VFA)-rich streams effect of substrate composition and feeding regime on PHA productivity, composition and ]xo]yeTties , Journal of Biotechnology,vol. 151,no. l,pp. 66-76,2011. 

Abstract Studies have shown that the production of polyhydroxyalkanoate (PHA) from plant oils is more efficient than from sugars in terms of productivity. Among the various plant oils, pahn oil is the most efficiently produced oil in the world. The main application of pahn oil is as a source of dietary fat. The conversion of food grade substrates to non-food materials is of concern because of the increasing need to feed the rapidly growing human population. Therefore, the by-products of the plant oil industry may be a better feedstock for PHA production. Alternatively, non-food grade oils such as jatropha oil can be developed as a feedstock for PHA production. This chapter looks at the potential of jatropha oil as a possible feedstock for the biosynthesis of PHA. 

Kasuya K-i, Inoue Y, Doi Y (1996) Adsorption kinetics of bacterial PHB depolymerase on the surface of polyhydroxyalkanoate films. Int J Biol Macrom 19 35 0 Kasuya K-i, Ohura T, Masuda K, Doi Y (1999) Substrate and binding specificities of bacterial polyhydroxybutyrate depolymerases. Int J Biol Macromol 24 329-336 Kato M, M. HJB, Kang CK, Fukui T, Doi Y (1996) Production of a novel copolyester of 3-hydroxybutyric acid and medium-chain-length 3-hydroxyalkanoic acids by Pseudomonas sp. 61-3 from sugars Appl Microbiol Biotechnol 45 363-370 Kaushik N, Kumar K, Kumar S, Kaushik N, Roy S (2007) Genetic variability ruid divergence studies in seed traits and oil content of Jatropha (Jatropha curcas L.) accessions. Biomass Bioenerg 31 497-502... 

Kim DY, Kim YB, Rhee YH (2000) Eveduation of various carbon substrates for the biosynthesis of polyhydroxyalkanoates bearing functional groups by Pseudomonas putida. Int J Biol Macromol 28 23-29... 

Sheu D-S, Lee C-Y (2004) Altering the substrate specificity of polyhydroxyalkanoate synthase 1 derived from Pseudomonas putida GPol by localized semirandom mutagenesis. J Bacteriol 186 4177-4184... 

Yuan W, Jia Y, Han J, SneU K, Miih U, Sinskey A et til (2001) Class I and III polyhydroxyalkanoate synthases from Ralstonia eutropha and Allochrorruitium vinosum characterization and substrate specifidty studies. Arc Biochem Biophys 394 87-98 Yusoff S (2006) Renewable eneigy from palm oil—Innovation on effective utilization of waste. J Cleaner Prod 14 87-93... 

Abstract Polyhydroxyalkanoates (PHA) are intracellular polymers stored by many bacterial species. Presently PHA arc industrially produced by pure cultures fermentation where high quality substrates are used. Mixed cultures using raw substrates are able to produce PHA when submitted to transient conditions like oscillations on substrate feeding or on oxygen supply. The yield on PHA produced by activated sludge submitted to these dynamic conditions reach values comparable to those obtained by the pure cultures, being the first process less cost intensive than die last one. The chain length of the polymer produced in both processes is similar. 

Polyhydroxyalkanoates (PHA) are polymers synthesised by bacteria as intracellular carbon and energy sources. PHA are industrially produced by pure cultures psing as main substrates glucose and propionic acid. The major expenses in the PHA production are determined by the cost of substrate and extraction of polymer from inside the cells. ... 

Satoh, H., Mino, T. and Matsuo, T., 1992, Uptake of organic substrates and accumulation of polyhydroxyalkanoates linked with glycolysis of intracellular carbohydrates under anaerobic conditions in the biological excess phosphate removal processes. Wat. Sci. Technol, 26 933-942. 

Polyhydroxyalkanoates biosynthesis is regulated, on one hand, by the activity of 3-ketothiolase (EC 2.3.1.16), and on the other hand of acetoacetyl-CoA reductase (EC 1.1.1.36) intracellular PHA breakdown is dependent on the activity of 3-hydroxybutyrate dehydrogenase (EC 1.1.1.30). Besides these three enzymes, the following compounds can be pointed out as major factors responsible of the activities of the key enzymes acetyl-CoA, free CoA, NAD(P) + (or NAD(P)H2, respectively) and, to a lower extent, ATP, pyruvate and oxalacetate. In any case, acetyl-CoA can be considered as the central metabolite both for biomass formation and PHB biosynthesis. This compound stems from the catabolic break down of carbon substrates like sugars (mainly catabolized by the 2-Keto-3-desoxy-6-phosphogluconate pathway) or fatty acids (converted by 6-oxidation). 

Polyhydroxyalkanoate synthases can use many different substrates and the number of viable pathways for the biosynthesis of PHAs is huge. When new substrates are used, novel PHAs can be produced. In aiming to reduce production costs, it will be useful to search for bacteria that can synthesize precursor substrates from simple and cheap carbon sources [36,92]. It has also been revealed that, when a PHA synthase enzyme is expressed in a different host microbe, it may result in different substrate speciflcity and therefore new PHAs with new chemical and physical properties are accessible [11]. 

Koller, M., Horvat, P., Hesse, P.l. et al. (2006) Assessment of formal and low structured kinetic modeling of polyhydroxyalkanoate synthesis from complex substrates. Bioprocess and Biosystems Engineering, 29(5-6), 367-377. 

Chen JY, Liu T, Zheng Z, Chen JC, Chen GQ (2004) Polyhydroxyalkanoate synthases PhaCl and PhaC2 from Pseudomonas stutzeri 1317 had different substrate specificities. FEMS Microbiol Lett 234 231-237... 

Aldor AS, Keasling JD (2003) Process design for microbial plastic factories metabolic engineering of polyhydroxyalkanoates. Curr Opin Biotechnol 14 475-483 Ashby RD, Solaiman DKY, Fogha TA, Liu CK (2001) Glucose/hpid mixed substrates as a means of controUing the properties of medium chain length poly(hydroxyalkanoates). Biomacromolecules 2 211-216... 

Polyhydroxyalkanoates (PHAs) represent an important group of biodegradable plastics. They are produced by various bacteria in many grades, differing in composition, molecular weight and other parameters [1, 2]. The formation of a particular material, either homo or copolymra depends on the type of bacteria, but even more important are the conditions of polymer formation, mainly the substrate used for feeding the bacteria and the conditions of their growth. 

Many workers have used PyMS to study the structures of polymers, both natural and artificial. Understanding the performance of polymers in terms of cohesion and substrate adhesion is of immense commercial significance in the paint and adhesive industries. Similarly, the behavior of polymers under stress and when exposed to external factors such as ultraviolet light has been extensively studied by PyMS and is useful in the development of novel materials that have desirable properties, e.g., fire-retardant coatings and biodegradable fibers. There is much interest in polyhydroxyalkanoates as potentially biodegradable plastics, and PyMS has been a principal method used to study thermal degradation profiles of this material. Similarly, in forensic science, PyMS has been used to analyze fibers and to help match samples of automotive finishes to paint chips found at crime scenes. 

Polyhydroxyalkanoates (PHAs) are naturally produced by microorganisms from various carbon substrates as a carbon or energy reserve. A wide variety of prokaryotic organisms (De Koning 1993 Madison and Huisman 1999) accumulate PH A from 30% to 80% of their cellular dry weight Biotechnological studies revealed that... 

Table 8.1 Classification of polyhydroxyalkanoate synthases based on their subunit composition and substrate specificity (Rehm, 2003)...

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