Production of ε-poly-L-lysine by newly isolated Kitasatospora sp. PL6-3

A novel ε-poly-L-lysine (ε-PL)-producing strain PL6-3 was isolated from soil, and was identified as a strain of Kitasatospora sp. This is the first detailed report of production of ε-PL by a strain in the genera of Kitasatospora. By controlling the culture pH at 4.0, the yield of ε-PL from PL6-3 reached 13.9 g/L after 120 h of cultivation in fed-batch fermentation. The morphological characteristics of Kitasatospora sp. PL6-3 in culture broth were different from those reported from strains of Streptomycetaceae, as no mycelium pellets were observed during the course of fermentation of PL6-3, which was beneficial to the assimilation of nutrition and secretion of the products. Furthermore, the molecular mass of the purified ε-PL from PL6-3 was determined to be 5.01 kDa by SDS-PAGE and 5.05 kDa by gel permeation chromatography, indicating that the ε-PL produced by this strain might be composed of 40 lysine residues. Usually, ε-PL with more lysine residues showed higher antimicrobial activity; however, it was difficult to obtain ε-PL with more than 36 lysine residues in this study. As a result, ε-PL from Kitasatospora sp. PL6-3, which contains more lysine residues than that from other strains, is more promising in the field of food preservatives.