Isolation and characterization of a novel ε-poly-L-lysine producing strain: Streptomyces griseofuscus

epsilon-poly-l-lysine (epsilon-PL) is a homo-poly-amino acid of l-lysine which is used as a safe food preservative. The productivity of epsilon-PL in currently reported wild type strains is low. This study was aimed at finding novel epsilon-PL producing strains with higher productivity and new fermentative characters. An improved detection method was employed using methylene blue as an epsilon-PL secretion indicator. 137 strains forming transparent circles were isolated. The best one was identified as Streptomyces griseofuscus according to the morphological characteristics and the comparison of internal transcribed spacer (ITS) ribosomal DNA (rDNA) gene sequences. The fermentative behavior of S. griseofuscus was investigated, and the epsilon-PL production was enhanced to 2.3 g/L in 5-L bioreactor by a pH control strategy. The yield of epsilon-PL reached 7.5 g/L in the fed-batch process. Compared with the reported wild type strains, S. griseofuscus produced relatively higher amounts of epsilon-PL, and might be a promising Streptomyces for epsilon-PL production.