Enhance nisin yield via improving acid-tolerant capability of Lactococcus lactis F44.
Enhance nisin yield via improving acid-tolerant capability of Lactococcus lactis F44.
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通过提高乳酸乳球菌 F44 的耐酸能力来提高乳链菌肽产量
DOI：
10.1038/srep27973
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发表时间：
2016-06-16
影响因子：
4.6
通讯作者：
Qiao J
中科院分区：
文献类型：
--
作者：
Zhang J;Caiyin Q;Feng W;Zhao X;Qiao B;Zhao G;Qiao J
传统上，乳链菌肽的工业化生产是通过使用乳酸乳球菌在中性发酵过程中。乳酸链球菌素在酸性环境中具有较高的活性。如何平衡细菌正常生长和乳酸链球菌素活性的pH值可能是关键问题。本研究将17个耐酸基因和6个乳酸合成基因导入L. lactis F44。与出发菌株F44的2810 IU/mL相比，过表达hdeAB、ldh和murG的工程菌的乳链菌肽效价分别提高到3850、3979和4377 IU/mL。这些工程菌在发酵过程中表现出更稳定的胞内pH值。乳酸产量的提高可以为耐酸性基因的表达提供部分额外的能量。hdeAB、murG和ldh（Z）在菌株F44中的共过表达导致乳链菌肽滴度为4913 IU/mL。工程菌（ABGL）能在pH4.2的平板上生长，而F44菌株在pH4.6的平板上存活。补料分批发酵结果表明，共表达L.乳酸菌菌株在较低的pH条件和较长的培养时间下可达到5563 IU/mL。本研究为构建工业生产中的稳定菌株提供了一种新的策略。
Traditionally, nisin was produced industrially by using Lactococcus lactis in the neutral fermentation process. However, nisin showed higher activity in the acidic environment. How to balance the pH value for bacterial normal growth and nisin activity might be the key problem. In this study, 17 acid-tolerant genes and 6 lactic acid synthetic genes were introduced in L. lactis F44, respectively. Comparing to the 2810 IU/mL nisin yield of the original strain F44, the nisin titer of the engineered strains over-expressing hdeAB, ldh and murG, increased to 3850, 3979 and 4377 IU/mL, respectively. These engineered strains showed more stable intracellular pH value during the fermentation process. Improvement of lactate production could partly provide the extra energy for the expression of acid tolerance genes during growth. Co-overexpression of hdeAB, murG and ldh(Z) in strain F44 resulted in the nisin titer of 4913 IU/mL. The engineered strain (ABGL) could grow on plates with pH 4.2, comparing to the surviving pH 4.6 of strain F44. The fed-batch fermentation showed nisin titer of the co-expression L. lactis strain could reach 5563 IU/mL with lower pH condition and longer cultivation time. This work provides a novel strategy of constructing robust strains for use in industry process.