Enhancement of ε-polylysine production by Streptomyces albulus strain 410 using pH control

The enhancement of epsilon -poly-L-lysine (epsilon -PL) production by Streptomyces albulus strain no. 410 (S410) by means of a pH control strategy was investigated. S140 cells produce epsilon -PL at a high concentration if the culture pH remains at about 4.0; however, if it shifts to higher than 4.0, the accumulated epsilon -PL is depolymerized. We therefore suggest a pH control strategy for cell growth and epsilon -PL production aimed at increasing the amount of epsilon -PL produced. The cultivation was divided into two control phases. In phase I, cell growth was accelerated by maintaining the pH at higher than 5.0; in phase II, epsilon -PL production was increased by maintaining the pH at about 4.0. To avoid an increase in the pH during phase II as a result of glucose depletion, the glucose concentration was kept at around 10 g/l by glucose feeding. This control strategy enhanced the production of h-PL to 48.3 g/l from 5.7 g/l in the case of batch culture.