Studies On The Fermentation Medium Optimization And Process Of Spinosad

Spinosad,a secondary metabolite of soilactinomycete, Saccharopolyspora spinosa, is a new biological pesticide, which can effectively control most varieties of pests, including lepidopterans, Lepidoptera, Orthoptera,Diptera and Coleopterans and has the features of broad spectrum, highly insecticidal activity and safty to non-target organisms.Appropriate fermentation conditions are the basis of strains which have the high yield of fennentation performance characteristics expressing its characteristics and producing more products.Using statistical method to increase the production of spinosad by Saccharopolyspora spinosa is the aim of our study.First of all,corn steep liquor,glucose and methyl oleate(MEO)were found to be the most important factors affecting spinosad production using Plackett-Burman design from 8 factors of glucose,soluble starch,corn steep liquor,cotton seed flour,soybean flour,yeast extract, CaCO3,and methyl oleate(MEO).And then, steepest ascent method which gradually moving in the direction of the largest increment could help us reach the optimum region.At last, central composite design(CCD) and response surface methodology(RSM) were applied to determine the optimal concentration of the selected significant variables.We get a second-order polynomial experimential model which express the good relationship of variables and response as the R2 is 94.75%. The optimum fermentation medium for spinosad production were as follows:glucose 48.6 g/L,soluble starch 10 g/L, corn steep liquor 7 g/L, cotton seed flour 22.5 g/L,soybean flour 5 g/L,yeast extract 2 g/L, CaCO35 g/L,methyl oleate (MEO) 36 g/L.The yield of spinosad and productity were increased 29.6% and 85.1%,repectively, in a 20 L bioreactor using the optimized medium.Temperature is an important factor which influence fermentation process. Studied the kinetics property of the batch fermentation of spinosad under different temperatures (26℃～32℃) and the effects of temperature on cell growth, products formation and substrate consumption. A higher temperature was prefered to hasten cell growth while in the favor of increasing the production of spinosad,a lower temperature was needed. A three-stage temperature control strategy was used to enhance productivity of spinosad:0-48 h the temperature was kept at 30℃,48～192 h the temperature was kept at 28℃,and at the last 48 h,switched the temperature to 30℃again. At last,spinosad production was 383.6 mg/L with a fermentation cycle of 7 days,which increased by 12.06% than that of 30℃,and the spinosad productivity increasd 11.35%.Dissolved oxygen concentration (DO) have great impact on the fermentation titer in aerobic fermentation process.Studied the conditions of cell growth, substrate consumption and synthesis of spinosad under different dissolved oxygen concentration and found that the higher the dissolved oxygen the better of the production of spinosad and the yield of spinosad with the DO keeping at 50% increased 60.54% and 88.5% than that of 30% and 40% respectively.