Optimization of poly-epsilon-lysine production by Streptomyces noursei NRRL 5126.

Poly-epsilon-lysine (epsilon-PL) is a non-toxic biopolymer with antimicrobial properties. The production of epsilon-PL by Streptomyces noursei NRRL 5126 shake-flask culture was optimized by identifying the most significant medium components which affect epsilon-PL production (glycerol, proteose peptone and ammonium sulphate) by Placket-Burman design and by application of an evolutionary operation (EVOP) to determine the optimal concentrations of these components. The epsilon-PL yield increased from 41.81 g/l in basal medium to 98.07 g/l in the EVOP-optimized medium containing 3% glycerol, 1% proteose peptone and 0.8% ammonium sulphate. Further improvements in media composition and culture conditions will be required to obtain yields comparable to those obtained with current commercial strains such as Streptomyces albulus. Copyright 2010 Elsevier Ltd. All rights reserved.