Metabolomics Studies On The Impact Of Dissolved Oxygen On The Spinosad Production By Saccharopolyspora Spinosa

Spinosad is a new class of macrolide compounds produced by aerobicfermentation of the Gram-positive bacteria Saccharopolyspora spinosa. Spinosadhas shown broad-spectrum insecticidal activity and has an excellentenvironmental and mammalian toxicological，so it was applied widely. The aim ofthis work is to increase the productivity of spinosad fermentation. After culturecondition optimization, the spinosad productivity is increased greatly. This workprovides reference for the industrialization of spinosad fermentation.In this paper, the carbon source of genetically engineered bacteria S. spinosa LU104was optimized and the production of spinosad increased by13.89%. Theproduction of spinosad reached417.96mg/L by adding0.5%Tween80at72h. Thecoupling of fermentation and separation with50g/L of macroporous resin adsorptionenhanced the biosynthesis of spinosad, and the production improved14.45%.According to the characteristics of the fermenter, the reflux device was improved todecrease the evaporation rate from10mL/h to4mL/h and the spinosad productionincreased by20%. Then, the gauze was wrapped on the paddle and baffle to reduceshear force and immobilize the cells and the spinosad yield improved by11.17%compared with the control group.In order to alleviate the oxygen limitation in the fermentation,0.5%n-dodecanewas added at120h and spinosad yield was57.8%higher than that of control group.The global GC-MS metabolomics analysis was performed to further illustrate themechanism of bacterial metabolism with and without n-dodecane.The results showedoxygen level was increased by adding n-dodecane and the enhanced level of primarymetabolism promoted cell growth and synthesis of precursors and cofactors. Thebiosynthesis of spinosad is a process of aerobic metabolism, so the increaseddissolved oxygen was also more conducive to improving the metabolic flux ofsecondary metabolites.Fed-batch culture was performed to improve the yield of spinosad, and theglucose of100g/L was fed at120h with a flow rate of14mL/h. The total volume was1L and the fed time was71.4h. Spinosad productivity was360.84mg/L, which was2.29-fold higher than that of batch fermentation. The kinetic models for biomass, substrate consumption and spinosad production were studied for the S. spinosa LU104by fed-batch fermentation. The experimental values and the predicted values fittedwell, and the correlation coefficients of three models were0.9984,0.9855and0.9793.Under the most optimal conditions, the production of spinosad in5L fermentorreached583.86mg/L, which was3.72-fold higher than that of original conditions.