Construction of engineered Streptomyces albulus by increasing ATP and NADH supply and efficient production of ε-poly-L-lysine from sweet potato powder.

ε-Poly-L-lysine (ε-PL), a broad-spectrum and efficient preservative, is widely used in food and pharmaceutical industries. In this study, the construction of engineered Streptomyces albulus by increasing ATP and NADH supply was carried out. Initially, the engineered strain BP3 was constructed by overexpressing pncB, pck, and pdh genes in S. albulus FL21. At 72h, both ATP and NADH levels in BP3 significantly increased compared to the control strain, while NADH/NAD ratio decreased. Consequently, ε-PL production by BP3 reached 1.61 g/L, representing a 30.89% increase over that of the control. Subsequently, when sweet potato powder (SPP) was used as carbon source, ε-PL production by BP3 achieved 1.44 g/L at 100 g/L SPP. Furthermore, transcriptomic analysis indicated that 712 upregulated genes and 743 downregulated genes were identified. Among them, the upregulated genes of asd, nadE and cs related to energy and redox reaction contributed to ε-PL production enhancement. Conversely, downregulation of aspA and gabD genes in competitive pathway redirected metabolic flux toward ε-PL biosynthesis. Finally, the ε-PL production of fed-batch fermentation reached 37.21 g/L and 33.85 g/L using glucose and SPP in a 5-L bioreactor, respectively. In summary, this study provides a valuable reference for the efficient ε-PL production.