State Key Laboratory of Materials-Oriented Chemical Engineering, College of Food Science and Light Industry, Nanjing Tech University, Nanjing, 211816, China.
Jiangsu National Synergetic Innovation Center for Advanced Materials, Nanjing Tech University, Nanjing, 211816, China.
Bioprocess Biosyst Eng. 2018 Sep;41(9):1337-1345. doi: 10.1007/s00449-018-1961-9. Epub 2018 Jul 5.
The antibacterial polymer ɛ-poly-L-lysine (ε-PL) has been widely used as a safe food preservative. As the synthesis of ε-PL requires a rich supply of nitrogen, the efficiency of nitrogen translocation and utilization is extremely important. The objective of this study was to improve the production of ε-PL by overexpressing the ammonium transporter gene amtB in Streptomyces albulus PD-1. Using the recombinant bacteria, the optimum carbon-to-nitrogen ratio in the synthesis stage of fermentation increased from 3 to 4.71, compared with that obtained using the wild-type strain, and the utilization efficiency of ammonium was improved too. Ultimately, the production of ε-PL increased from 22.7 to 35.7 g/L upon fed-batch cultivation in a 5 L bioreactor. Determination of the expression of the genes and enzymes associated with ammonium metabolism and ε-PL synthesis revealed that the overexpression of amtB in S. albulus PD-1 enhanced ε-PL biosynthesis by increasing the activity of the corresponding metabolic pathways. To the best of our knowledge, this is the first report on enhancing ε-PL production by overexpression of the amtB gene in an ε-PL-producing strain.
抗菌聚合物 ε-聚赖氨酸（ε-PL）已被广泛用作安全的食品防腐剂。由于 ε-PL 的合成需要丰富的氮源供应，因此氮的转运和利用效率极其重要。本研究的目的是通过在白色链霉菌 PD-1 中过表达铵转运体基因 amtB 来提高 ε-PL 的产量。使用重组菌，发酵合成阶段的最佳碳氮比从野生型菌株的 3 提高到 4.71，铵的利用效率也得到了提高。最终，在 5 L 生物反应器中进行分批补料培养后，ε-PL 的产量从 22.7 g/L 增加到 35.7 g/L。与铵代谢和 ε-PL 合成相关的基因和酶的表达测定表明，在白色链霉菌 PD-1 中过表达 amtB 增强了 ε-PL 的生物合成，从而增加了相应代谢途径的活性。据我们所知，这是首次在 ε-PL 生产菌株中通过过表达 amtB 基因来提高 ε-PL 产量的报道。
