玉米粉细菌发酵生产L-乳酸的研究

L-lactic acid zymotechnics using corn flour

以玉米粉为细菌L-乳酸发酵的主要原料,不仅可以提高玉米的利用价值,而且可以降低L-乳酸的生产成本。将玉米粉经过双酶法得到的玉米糖化液为L-乳酸发酵的主要碳源,寻求适合细菌TL-2发酵生产L-乳酸的氮源及其合适的添加量。比较了几种不同平板培养基TL-2的生长情况,得出小肽-3可作为乳酸发酵培养基的有机氮源;在最初发酵培养基的基础上,改变其有机氮源及其含量,由发酵试验得,同样产酸量时,以10 g/L小肽-3为唯一氮源的发酵液的颜色最浅;并在此基础上,利用响应面分析法,得出初糖浓度:小肽-3为15.5∶1,摇床培养(通风)时间为24.27 h时,乳酸的产量最高。在此培养方式及培养基的基础上进行摇瓶发酵,乳酸产量为143.8 g/L,转化率为95.8%,发酵周期缩短为60 h。

Corn flour as a main raw material for producing L-lactic acid, not only be able to improve corn＇s values in use, but also be able to reduce the production cost of L-lactic acid. The corn sacchrification liquid by doubleenzyme hydrolysis could be a main carbon source for L-lactic aid fermentation, then suitable organic nitrogen sources for lactic acid bacteria TL-2 was explored. Results show that peptide-3 can be organic nitrogen in the fermentation culture medium to produce L-lactic acid through comparing the TL-2 growth condition in several different flat media. When organic nitrogen sources and their concentrations are changed on the basis of initial medium, the same yield of L-lactic acid is obtained, but the color of fermentation liquid which containing 10 g/L peptide-3 is the lightest. Response surface methodology were applied to optimize three factors of medium. When the ratio of sugar concentration to peptide-3 is 15.5 ：1, shaking time is 24. 27 h, the yield of L-lactic acid is the largest. The fermentation form and optimized medium allow lactic acid yield to 143.8g/L in flask-shaking, sugar utilization to 95.8%, fermentation period shortens to 60 h.