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.
ABSTRACT
The potential of Rhizobium sp. N613 to produce the exopolysaccharide (REPS) was studied in this paper. Using an orthogonal design in a flask-shaker culture system, the fermentation medium and conditions of synthesizing REPS were optimized. Based on these results, the fermentation kinetic parameters were obtained in the batch fermentation with a 10L fermentor. The REPS yield of 11.31g/L was achieved by metabolic regulation during 40 h fed-batch fermentation. Transplanted tumor models of sarcoma 180 in mice were used to evaluate the anti-tumor effect. The result of anti-tumor activities showed that inhibition rate was 53.40%, when dose of REPS was 5mg/kg. These results indicate that REPS has the following properties: the short duration of fermentation, the high yield, the low cost, the effective immunocompetence and thickening. Thus, REPS has the value of development and application.