title: Enhancement of ε-poly-lysine production in ε-poly-lysine-tolerant Streptomyces sp. by genome shuffling.
abstract: ε-Poly-L-lysine (ε-PL) has been widely used as food additive. However, the self-inhibition of ε-PL on cell growth limits the accumulation of ε-PL in the wild-type strain. Here, we screened ε-PL-tolerant strain of Streptomyces sp. with higher ε-PL productivity by genome shuffling and studied the mechanism for the improvement. The initial mutant library was constructed by diethyl sulfate mutagenesis. After four rounds of protoplast fusion, a shuffled strain F4-22 with 3.11 g/L ε-PL productivity in shake flask, 1.81-fold in comparison with that of parent strain, was obtained. The higher aspartokinase activity was induced in F4-22 whereas no obvious changes have been found in ε-PL synthetic and degrading enzymes which indicated that the upstream reregulation of the precursor lysine synthesis rather than lysine polymerization or ε-PL degradation in shuffled strain accounted for the higher productivity. The activities of key enzymes in the central metabolic pathway were also enhanced in F4-22 which resulted in increased vigor of the strain and in delayed strain lysis during fermentation. These improved properties of shuffled strain led to the success of combining general two-stage fermentation into one-stage one in 5-L bioreactor with 32.7 % more ε-PL production than that of parent strain. The strategy used in this study provided a novel strain breeding approach of producers which suffered from ε-PL-like self-inhibition of the metabolites.
authors.affiliation: Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, Jiangsu, China.
authors.forename: Yong-Peng
authors.initials: YP
authors.lastname: Zhou
authors.forename: Xi-Dong
authors.initials: XD
authors.lastname: Ren
authors.forename: Liang
authors.initials: L
authors.lastname: Wang
authors.forename: Xu-Sheng
authors.initials: XS
authors.lastname: Chen
authors.forename: Zhong-Gui
authors.initials: ZG
authors.lastname: Mao
authors.forename: Lei
authors.initials: L
authors.lastname: Tang
mesh_terms: D032621:DNA Shuffling / Q000379:methods*; D004361:Drug Tolerance / Q000235:genetics; D024861:Genetic Enhancement / Q000379:methods*; D016680:Genome, Bacterial / Q000235:genetics*; D011107:Polylysine / Q000096:biosynthesis* / Q000235:genetics; D011995:Recombination, Genetic / Q000235:genetics; D013045:Species Specificity; D013302:Streptomyces / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D011107:Polylysine