Enhancement of ε-poly-l-lysine production by overexpressing the ammonium transporter gene in Streptomyces albulus PD-1

• DOI: 10.1007/s00449-018-1961-9
• Publication Date: 2018-07-05T15:21:27Z
• Authors: Delei Xu; Haiqing Yao; Changhong Cao; Zhaoxian Xu; Sha Li; Zheng Xu; Jiahai Zhou; Xiaohai Feng; Hong Xu
• Keywords: 2. Zero hunger; 0303 health sciences; 03 medical and health sciences; Bacterial Proteins; Gene Expression; Polylysine; Cation Transport Proteins; Streptomyces

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.