Fermentative Production Of Acetoin With High Ee Value By Wild-type Strains

Acetoin is widely used in food,medicine,agriculture,cosmetics and many other fields,and has a broad application prospect and economic value.In recent years,there are plenty of researches on producing natural acetoin by microbial fermentation while fewer studies have been performed on chiral acetoin.This paper studies fermentative production of acetoin with high ee(enantiomeric excess)value,from the following three aspects.First,employing weight assignment method to analyze acetoin and its ee value.In this experiment,Bacillus sp.H15-1 has been used to produce acetoin.After detection of the product by gas chromatography equiped with chiral column,in order to combine the yield and ee value into a target value,the experimental analysis is optimized.First,the acetoin yield and ee value separately normalized processing,and gives different weights to its comparison.The yield of acetoin and its ee value are normalized separately and then assigned with different proportion.finally we think acetoin ee value account for 70% of the weight,30% weighting acetoin production is more appropriate.Secondly,selecting bacterial strains and optimizing temperature and pH conditions.The bacterial strain Bacillus sp.H-18 W which has relatively high acetoin ee value and yield is obtained by screening all the acetoin-producing strains in the laboratory.The optimum pH was 6.7 and the optimum temperature was 45? after optimizing the culture conditions.The initial concentration of glucose in this experiment was 20 g/L.After cultured in constant temperature shaker at 120 rpm for 10 hours,the yield of acetoin was 6.66 g/L while the acetoin ee value was 90.32% and the transformtion rate was 87.55%.Finally,fermenting with soybean meal hydrolysate.The experiment of producing acetoin through Bacillus sp.H-18 W showed that the optimum dilution ratio of the hydrolysate and water was 1:4 and the best medium formulation was the soybean meal hydrolyzate obtained from acidic and neutral proteases when soybean meal hydrolysate was used as the culture medium.We also found that the yield of acetoin and the weight assignment results reached the peak at 2 hours after the glucose was exhausted.The final experiment was performed using the optimized conditions.The outcome showed that glucose will be exhausted within 60 h,and the yield of acetoin reached its highest of 22.02 g/L at 62 h while the ee value was 95.93% and the transformtion rate was 85.43%.