OPTIMIZATION OF MEDIUM COMPONENTS AND FEEDING STRATEGIES FOR EPSILON POLY-L-LYSINE PRODUCTION BY STREPTOMYCES NOURSEI NRRL 5126

Epsilon poly-L-lysine (ε-PL) is a nontoxic biopolymer widely used in food and pharmaceutical industry. The present work reports the nutritional requirements for submerged fermentation of Streptomyces noursei NRRL 5126 using a combination of one factor at a time and statistical orthogonal array method. Two-fold increase in ε-PL productivity (74 mg/L) was observed using optimized medium containing glycerol as carbon source along with proteose peptone and ammonium sulphate as nitrogen source. Various metabolic precursors such as amino acids, tricarboxylic acid cycle intermediates were investigated for improved production of ε-PL.  Four fold increase (74 mg/L to 310 mg/L) in ε-PL production was achieved by incorporation of L-aspartate (2mM) and citric acid (5mM). Fed batch fermentation for ε-PL production with intermittent feeding with glycerol and in combination with metabolic precursors was studied. Fed batch fermentation with intermittent feeding of glycerol gave a maximum yield of 233 mg/L. Productivity was further enhanced and reached a maximum of 408 mg/L by addition of glycerol along with 5 mM citric acid after 24 h and 2 mM L-aspartate after 36 hours respectively