Enhanced ε-Poly-L-Lysine Production by the Synergistic Effect of ε-Poly-L-Lysine Synthetase Overexpression and Citrate in Streptomyces albulus
Enhanced ε-Poly-L-Lysine Production by the Synergistic Effect of ε-Poly-L-Lysine Synthetase Overexpression and Citrate in Streptomyces albulus
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DOI：
10.3389/fbioe.2020.00288
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发表时间：
2020-04-22
影响因子：
5.7
通讯作者：
Yu, Bo
中科院分区：
文献类型：
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作者：
Wang, Aixia;Tian, Wenzhe;Yu, Bo
ε-聚-L-赖氨酸（ε-PL）是一种通过微生物发酵生产的天然氨基酸聚合物。它主要用作食品和化妆品工业中的防腐剂、药物中的药物载体以及基因治疗中的基因载体。 ε-PL合酶是负责L-赖氨酸聚合形成ε-PL的关键酶。在本研究中，利用 kasOp* 启动子和噬菌体 phi C31 衣壳蛋白的核糖体结合位点，在白色链霉菌 CICC 11022 中过度表达 epsilon-PL 合酶基因，从而产生了基因工程菌株 Q-PL2。在摇瓶发酵中，Q-PL2产生的epsilon-PL滴度比野生菌株产生的滴度高88.2%+/-8.3%。在2 g/L柠檬酸钠的协同作用下，Q-PL2产生的epsilon-PL滴度比野生菌株高出211.2%+/-17.4%。在补料分批发酵中，S. albulus Q-PL2 在 72 小时内产生了 20.1 +/- 1.3 g/L 的 epsilon-PL，生产率为 6.7 +/- 0.4 g/L/天，是野生菌株产生的 3.2 +/- 0.3 倍。这些结果表明epsilon-PL合酶是epsilon-PL合成途径中的限速酶之一，为通过代谢工程进一步提高S. albulus的epsilon-PL生产能力奠定了基础。
epsilon-Poly-L-lysine (epsilon-PL) is a natural amino acid polymer produced by microbial fermentation. It has been mainly used as a preservative in the food and cosmetics industries, as a drug carrier in medicines, and as a gene carrier in gene therapy. epsilon-PL synthase is the key enzyme responsible for the polymerization of L-lysine to form epsilon-PL. In this study, the epsilon-PL synthase gene was overexpressed in Streptomyces albulus CICC 11022 by using the kasOp* promoter and the ribosome binding site from the capsid protein of phage phi C31, which resulted in a genetically engineered strain Q-PL2. The titers of epsilon-PL produced by Q-PL2 were 88.2% +/- 8.3% higher than that produced by the wild strain in shake flask fermentation. With the synergistic effect of 2 g/L sodium citrate, the titers of epsilon-PL produced by Q-PL2 were 211.2% +/- 17.4% higher than that produced by the wild strain. In fed-batch fermentations, 20.1 +/- 1.3 g/L of epsilon-PL was produced by S. albulus Q-PL2 in 72 h with a productivity of 6.7 +/- 0.4 g/L/day, which was 3.2 +/- 0.3-fold of that produced by the wild strain. These results indicate that epsilon-PL synthase is one of the rate-limiting enzymes in epsilon-PL synthesis pathway and lays a foundation for further improving the epsilon-PL production ability of S. albulus by metabolic engineering.