Download Ecology of mixed cultures producing PHA

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