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Ecology of mixed cultures producing PHA PhD-student: Yang Jiang Tel: +31-15-2781482 E-mail: [email protected] Promotor: Prof. dr. ir. M.C.M van Loosdrecht Supervisor: Dr. G. Muyzer, Dr. ir. R. Kleerebezem Institute: Delft University of Technology, Department of Biotechnology, Environmental Biotechnology Group Project term: Oct 2006 – Oct 2010 Financed by: The Netherlands Ministry of Economic Affairs and the BBasic partner organizations (www.b-basic.nl) through BBasic, a public-private NWO-ACTS programme (ACTS = Advanced Chemical Technologies for Sustainability) Description Polyhydroxyalkanoates (PHAs) are a class of polyesters synthesised and accumulated as storage polymers for energy and substrate by many different groups of bacteria [1]. The potential industrial application of PHAs is the replacement of petrochemical plastics, because they are biodegradable and can be produced from renewable resources. The development of commercial production of PHAs focuses on pure cultures processes. High cost on substrates and operation limit pure culture PHAs production on a large scale. Compared to pure culture processes, the merit of mixed culture processes are lower costs but until now a shortcoming is the low productivity of PHA. In the past 20 years, more than 50 PHA synthase genes and other genes related to PHA biosynthesis have been identified. Figure 1 shows the key enzyme reactions of synthesis (e.g. phaA, phaB, phaC) and degradation (e.g. phaZ) of PHA in Azospirillum brasilense [2]. Apart from the enzymes shown in Figure 1, other proteins, such as the granule-associated proteins (e.g. phaP) and regulators (e.g.phaR) are involved in PHAs synthesis [3]. Different bacteria adopt various strategies to synthesize PHAs. Goal of this project is to obtain insight into the ecology of PHA-producing bacteria with the aim to improve the production of PHA. Different genomic tools will be used to study the diversity and expression of genes encoding key enzymes involved in PHA production. References [1] T.V.N. Ramachander, S.K. Rawal. PHB synthase from Streptomyces aureofaciens NRRL 2209. FEMS Microbiology Letters 242 (2005) 13–18 [2] Daniel Kadouri, Edouard Jurkevitch, and Yaacov Okon. Ecological and Agricultural Significance of Bacterial Polyhydroxyalkanoates. Critical Reviews in Microbiology, 31:55–67, 2005 [3] Anne Pohlmann, Wolfgang Florian Fricke et al. Genome sequence of the bioplasticproducing "Knallgas" bacterium Ralstonia eutropha H16. Nature biotechnology: 2006