ABSTRACT
The potential of a Sinorhizobium fredii strain producing a copolymer polyhydroxyalkanoate(PHA)from glucose and sodium decanoate substrates was studied in this paper.Using orthogonal design in a flask-shaker culture system,the culture medium,some culture conditions and vital regulation conditions for polymer synthesis were optimized.These optimized results were applied into further studies in two-stage fed-batch with a 10L fermentor.The whole culture process consisted of two stages,that is,the cell growth and the copolymer production.The first stage was for the cell growing to a desired biomass and the second was for the copolymer synthesis.For producing PHA polymers,the selected 8 mM sodium decanoate was added into the broth by adopting a two-step adding method for avoiding of foaming when the biomass had approached 28.5g/L dry cell.The maximum P(HB-HH)production could be 17.55 g/L with a monomer ratio of 79.4%(W/W)3-HB and 20.6%(W/W)3-HH.The molecule constitute of the copolymer is poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)[P(HB-HH)] and its molecular weight(MW)is 1.4?105D.The results demonstrated that the employed S.fredii strain could be a potential candidate for industrial production of the copolymer.The fermentation parameters acquired in the experimental system offered some valuable references for studying large-scale production of the copolymer.