Effects of Yeast Extract on Poly-ε-Lysine Production in Batch Culture of Streptomyces Albulus

Abstract

Yeast extract (YE) is a sole organic nitrogen source in a commonly medium 3G for Streptomyces albulus to produce poly-ε-lysine (ε-PL). In this study, five YEs from five commercial suppliers were used to evaluate their effects on the growth of Streptomyces albulus 213 and ε-PL production. YE from bakers’ yeast with the highest total nitrogen content (TN), α-amino nitrogen content (AN) or the ratio of AN/TN produced the highest yield of ε-PL, while YE from brewers’ yeast with the highest RNA content got the most dry cell weight (DCW). However, there was little correlation between TN, AN or AN/TN in YE and the yield of ε-PL. There was also weak correlation between RNA in YE and DCW. When 60% baker YE was mixed with 40% brewer YE, the yield of ε-PL reached 1.89 g/l and increased by 16% and 37% than those of baker YE and brewer YE, respectively. Furthermore, five kinds of vitamins and nine kinds of amino acids were screened to supplement baker YE. When 6 mg/l biotin, 5mg/l pantothenic acid, 0.7 g/l L-glutamine and 0.5 g/l L-arginine were mixed with baker YE in M3G, ε-PL reached maximum production respondent to 3.05 g/l that was 61.4% higher than control.