中和剂对大肠杆菌工程菌HBUT-L16发酵产L-乳酸的影响

该文对前期构建的产高光学纯度L-乳酸的大肠杆菌工程菌HBUT-L进行了耐乳酸钠的驯化，并对驯化前后菌株发酵产L-乳酸的中和剂进行了选择和对比。结果表明，经过28代驯化后的菌株HBUT-L16以Ca（OH）2作中和剂时发酵效果较NaOH为中和剂时效果好，L-乳酸产量、糖酸转化率及生产强度分别提高了6.6%、5.6%、44.4%。与驯化前菌株HBUT-L的发酵结果相比，HBUT-L16以Ca（OH）2为中和剂进行发酵时，乳酸产量提高了4.4%，糖酸转化率提高了2.8%，生产强度增加了26.71%；而以NaOH为中和剂时，对驯化前后菌株的发酵效果影响不大，由此推测耐乳酸钠的驯化主要通过提高工程菌对乳酸根的耐受性而非钠离子的耐受性，来提高L-乳酸的产量。

Effects of neutralizers on L-lactic acid yield by Escherichia coli HBUT-L16 fermentation

A previously engineered Escherichia coli with high yield of optical purity L-lactic acid was domesticated to resist sodium lactate, and neutralizer that evolved in strain fermentation for L-lactic acid production before and after domestication was selected and compared. Results showed that the strain HBUT-L16 which was adaptively evolved for 28 generation had a better fermentation effect with Ca(OH)2 as neutralizer comparing with that of NaOH as neutralizer, the L-lactic acid yield, sugar-acid conversion rate and productivity increased 6.6%, 5.6% and 44.4%, respectively. Comparing with the results of undomesticated strain HBUT-L, the strain HBUT-L16 produced 4.4% more L-lactic acid, 2.8% more conversion rate and 26.71% more productivity in the fermentation with Ca(OH)2 as neutralizer. While there was no obvious influence on the results using NaOH as neutralizer. So it suggested that the L-lactic acid yield was improved mainly by improving the tolerance of engineered strain for lactate but not for Na+.