Production of ε-poly-lysine by Streptomyces albulus PD-1 via solid-state fermentation

The aim of this study was to produce ε-poly-lysine (ε-PL) by Streptomyces albulus PD-1 through solid-state fermentation (SSF) using agro-industrial residues. Maximum ε-PL production (86.62 mg/g substrate) was obtained a mixed substrate of rapeseed cake and wheat bran (2:1, w/w) supplemented with glucose (4%, w/w), (NH₄)₂SO₄ (3%, w/w), with an initial moisture content of 65%, initial pH of 7.0 and inoculum size of 13% v/w, incubated at 30 °C for 8 days. The results of scanning electron microscopy indicated that the filamentous thallus could penetrate the substrate surface. Moreover, repeated-batch SSF was successfully conducted 8 times using 10% substrate as seeds for the next fermentation cycle, and the results suggest that repeated-batch SSF is more efficient because of the shortened lag phase. To the best of our knowledge, this is the first report on ε-PL production using the SSF process.