Metabolic precursors enhance the production of poly-ε-lysine by Streptomyces noursei NRRL 5126

Poly-epsilon-lysine produced by streptomyces species is a promising biopolymer owing to its antimicrobial activity and safety for humans. A number of nutritional factors influencing poly-epsilon-lysine production by Streptomyces noursei NRRL 5126 were studied. Various metabolic precursors such as amino acids, tricarboxylic acid cycle intermediates and cofactors were investigated for improved production of poly-epsilon-lysine. Results indicated L-aspartate (2 mM) and citric acid (5 mM) to substantially increase the poly-epsilon-lysine production from 97.08 to 409.94 mg/L. Addition of citric acid after 24 h and L-aspartate after 36 h of fermentation medium further enhanced poly-epsilon-lysine production to 497.67 mg/L after a total fermentation time of 108 h. However, the use of cofactors of enzymes involved in the biosynthesis of poly-epsilon-lysine inhibited its production which is believed to be due to diversion of the flux to other metabolites.