Effect of Yeast Extract on Production of ε-poly-L-lysine by Streptomyces diastatochromogenes

In order to discuss the effect of yeast extract on e-poly-L-lysine (e-PL) fermentation, the effect of yeast extract which are from different factories on fermentation of Streptomyces diastatochromogenes 6#-7 was performed. The result shows that there is a significant difference when adding yeast extract which are from different factories (p 0.05).In addition, the effect of different concentration of yeast extract in medium on fermentation of strain 6#-7 was investigated. When the concentration of yeast extract is 15 g/L, the e-PL yield of strain 6#-7 can be up to 1.34 g/L and has a 6-fold enhancement compared to the group without yeast extract. The study of the key enzyme activities indicated that the improvement of e-PL may be due to the concentration of yeast extract and the growing status of cell can be evaluated by the value of aspartokinase (Ask), e-PL synthetase (Pls) and homoserine dehydrogenase (HSD).