高温微好氧发酵策略强化重组大肠杆菌D-乳酸合成途径

Enhanced D-lactic acid production of recombinant E.coli by thermophilic micro-aerobic strategy

D-乳酸作为一种重要的手性中间体和聚乳酸合成的原料,其生产已越来越受到人们的重视。Escherichia coli CICIM B0013-070是一株能同型发酵合成D-乳酸的基因重组菌。比较该菌株不同温度、不同供氧强度下的生长情况及发酵产酸性能。结果显示,采用微好氧发酵,在37、40℃温度下菌体量仍在增长;当发酵温度高于42℃后,菌体生长受到一定抑制,菌体量保持稳定,而乳酸的比合成速率和乳酸得率均有所提高。另外,对比微好氧发酵和限氧发酵的乳酸比合成速率发现,前者为后者的1.5～2倍;且微好氧条件下,葡萄糖到乳酸的得率随温度的提高逐渐增加,较高温度下接近甚至超过了限氧条件相同发酵温度下的得率。上述结果表明,在非严格限氧的条件下,可以通过发酵温度的提高,实现发酵阶段菌体生长和D-乳酸合成的代谢流微调,维持D-乳酸高生产强度的同时提高D-乳酸得率。

D-lactic acid, as an important Chiral intermediate and the monomer of biodegradable synthetic materials D-polylactic acid, its production has attracted more attention. Escherichia coil strain CICIM B0013-070 is a genetic recombinant for homolactic fermentation. The growth and fermentation performance of B0013-070 was investigated at various temperatures. The results showed that the cell mass of the strain B0013-070 cultured at 37℃ and 40℃, was still increasingunder micro-aerobic condition. When the fermentation temperature was higher than 42 ℃, the growth of strain B0013-070 was inhibited, while the synthesis rate and the yield of lactic acid were both enhanced. Furthermore, the specific synthesis rate of lactic acid was increased to be 1.5-2 folds higher than cells were cultured at the same fermentation temperature under limited oxygen condition. In addition, the yield of lactic acid were increased with elevating the fermentation temperature, and higher yield was obtained under micro-aerobic condition at 50 ℃ than cells were cultured under limited oxygen condition. These results indicate that under non-strictly limited oxygen conditions, the coupling ralation of the cell growth and lactate synthesis can be particially released through the elevation of the fermentation temperature, and then the lactic acid productivity was improved.