Synthesis Of 2,3-Butanediol By Recycling Using Microbial Biomass

After the microbial fermentation, terminal biomass is usually not the products required. There are few effective energy-saving ways to dispose waste biomass. So waste biomass is decomposed in sewage treatment plant or burnt down, which not only pollutes the environment but also wastes a lot of natural resources and energy. In the process of synthesis of 2,3-butanediol by Serratia marcescens, there are a lot of waste biomass. The recycling using waste biomass was studied in this thesis.Firstly, repeated fermentation by recycling the terminal biomass of Serratia marcescens was studied. The time and amount to add biomass were examined. The repeated fermentation culture medium was optimized by single factor experiment and response surface experiment. The obtained result is:sodium acetate 25g/L with the addtion method of a small number of repeated; vegetable oil 0.3%; 30mL fermentation broth in 500mL shake flask.Then, after recycling the terminal biomass, the method of preparing lysate was developed successfully and the content of nitrogen in lysate was measured.Thirdly, the liability of lysate used as nitrogen instead of yeast extract partly was validated. In the fermentation process, the best ratio of lysate to yeast extract was tested. The effect of 5g/L yeast extract and the lysate equivalent of 20g/L yeast extract is best after 36 hours. At the end of fermentation, the yield of 2,3-butanediol is 83g/L, the yield of sucrose is 0.625g/g and the effect on the growth of microbe and synthesis of products by adding different metal Salts were tested.Finally, fermentation experiments by repeated recycling biomass more than once and fermentation experiments by lysate using as nitrogen which was prepared by biomass more than once were studied, and recycling using biomass time and again was realized during the fermentation.