Improvement of ε-poly-L-lysine production by Streptomyces albulus TUST2 employing a feeding strategy

摘要

Streptomyces albulus TUST2, separated from a soil sample of Hainan Island, was cultivated in a stirred, submerged aerated 5-1 bioreactor. Carbon source and nitrogen source effects were clarified in fed-batch fermentation, particularly glucose and ammonium sulfate feedings for enhancing the ε-poly-L-lysine (ε-PL) production were elucidated. The culture was divided into two control phases. In phase I, the pH was maintained at its initial 6.8 for 36h for acquiring high biomass; In phase II, the pH was maintained at 4.0 aiming at increasing the ε-PL accumulation. Moreover, pulsed feeding of glucose (800 g/l) was carried out accompanied by ammonium sulfate (80 g/l) discontinuously when their concentration reached a lower level (nearly 10 g/l) in the medium, so that the final concentration of glucose can be kept at 13g/l. By using this feeding policy, the elevation of antibacterial activity of ε-PL by S. albulus TUST2 is 16.67%, and its accumulation in 4-days cultivation is 20.20g/l. We have illuminated that substrate feeding strategy is a doable method for improving ε-PL production by S. albulus TUST2.