Production Of Microbial Exopolysaccharides By Strain Of Q9415

Optimization of cultural conditions, using agricultural byproducts as culture substrate, and addition of emulsifiers to fermentation substrate were carried out in this dissertation. Recovery of PS-9415 by ultrafiltration and extraction of exopolysaccharides by organic solvent were also studied. The results reached are mainly as following:1. The cultural conditions for bacterial exopolysaccharides produced by Agrobacterium radiobacter Q9415 were optimized by response surface methodology (rsm) to maximize the viscosity of the broth, the yield of the exopolysaccharides and the conversion efficiency of carbon source. The optimized conditions range are sucrose concentration(4%~5%), pH(6.5~8.0) and inoculum concentration 10% or higher. Shake flask fermentation experiment under optimized conditions reached the yield of 22.6g/L exopolysaccharide, conversion efficiency of 45.2% and broth viscosity of 2.01 Pa.s. Fermentation in 30 L bioreactor obtained higher yield (30g/L) and broth viscosity ( 4.6 Pa.s).2. Shake flask fermentation on glucose syrup (30g/L) and peptone produced 15.5g/L exopolysaccharides. Fermentation on sucrose and soybean byproducts obtained the yield of 13.2g/L, biomass of 2.15g/L and broth viscosity 1.28 Pa.s. Sugarcane molasses fermentation reached the yield of 13.9 g/L.3. The effects of the addition of emulsifier Tween 80, Tween 60, TritonX-100, sucrose ester, SSL and on Q9415 fermentation were examined both in shake flask and in 30L bioreactor. The results of shake flask fermentation exhibited that TritonX 100 and Tween 80 can effectively improve the yield and viscosity of the product. The optimum concentration and addition time of Triton X 100 to shake flask were 2.5g/L and 46~72h respectively. The addition of Triton X 100 to 30L bioreactor produced 28.5g/L exopolysaccharides at 86h, with higher viscosity.4. Logistic equation and L-P equation was applied to the kinetics studies of EPS production. Mathematical kinetic model describing the course of EPS fermentation were established. The experimental data and the models were...