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

ε-poly-L-lysine (ε-PL) is a homo-poly-amino acid of L-lysine which is used as a safe food preservative. The productivity of ε-PL in currently reported wild type strains is low. This study was aimed at finding novel ε-PL producing strains with higher productivity and new fermentative characters. An improved detection method was employed using methylene blue as an ε-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 ε-PL production was enhanced to 2.3 g/L in 5-L bioreactor by a pH control strategy. The yield of ε-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 ε-PL, and might be a promising Streptomyces for ε-PL production.