Improved ε-poly-l-lysine production of Streptomyces sp. FEEL-1 by atmospheric and room temperature plasma mutagenesis and streptomycin resistance screening

Abstract

To enhance the ε-poly-l-lysine (ε-PL) productivity of Streptomyces sp. FEEL-1, a novel breeding strategy of atmospheric and room temperature plasma (ARTP) mutagenesis with streptomycin resistance screening was developed. After three rounds of recursive breeding, one strain designated AS3-14 was selected with a ε-PL yield of 2.91 g/L in shake-flask fermentation, which was elevated by 66.3 % compared to that of the parent strain FEEL-1. Subsequent batch and fed-batch fermentation was performed in a 5 L fermenter, and 8.2 g/L and 41.2 g/L ε-PL productions were achieved, which were 49.1 % and 68.1 % higher, respectively, than those of the parent strain. Analysis of enzyme activities indicated that key enzymes, e.g., hexokinase, pyruvate kinase, citrate synthase and aspartate kinase, were more active in the mutant AS3-14 than in FEEL-1, which might explain the enhanced ε-PL productivity. The results of amplified fragment length polymorphism analysis indicated that the genomic DNA of AS3-14 became more variable after ARTP mutagenesis. Therefore, ARTP combined with streptomycin resistance is an efficient breeding approach for the rapid evolution of ε-PL-producing Streptomyces strains.