Optimization of very high ethanol fermentation conditions of the recombinant Zymomonas mobilis by response surface method

The recombinant bacteria Z.mobilis HYMX which can utilize glucose,xylose,arabinose and mannose to produce ethanol in the culture medium without amino acids and vitamins,was constructed by genetic engineering technology.The fermentation conditions of the HYMX strain under very high gravity ethanol fermentation conditions were optimized by the response surface methodology. The results showed that the optimum conditions were:glucose concentration 305 g / L,temperature 34 ℃,p H6.5,urea concentration 3 g / L,inoculation amount 10%,fermentation time 60 h.Under the optimized conditions,the ethanol yield of the recombinant strain was 153.1 g / L,8.5% higher than the non- optimized one,105.14% higher than the prototype strain. Compared with the industrial yeast strain PE-2,the glucose saving was more than 12%,and the fermentation time saving was more than 37.5%.