Microparticle-enhanced production of ε-poly-L-lysine in fed-batch fermentation

In this study, the effects of talc microparticles on mycelia morphology and epsilon-poly-L-lysine (epsilon-PL) production by Streptomyces sp. M-Z18 were investigated for the first time. Changing mycelia morphology with talc microparticles has resulted in epsilon-PL production being enhanced. Talc microparticles caused a decrease of pellet diameter from 297.63 +/- 156.33 to 205.65 +/- 71.56 mm in shake-flask fermentation. Moreover, the maximum epsilon-PL production reached 2.51 +/- 0.08 g L-1 in the presence of 10 g L-1 talc microparticles, which was increased by 50.30%, compared to the control (1.67 +/- 0.11 g L-1). The scale-up processes were performed in batch and fed-batch fermentations in a 5 L fermenter with 10 g L-1 talc addition, and the final epsilon-PL production of 30.57 g L-1 was obtained at 168 h, with 44.06% increase over the control. Talc microparticles of 10 g L-1 were then supplied to the fed-batch fermentation with acidic pH shock and agro-industrial by-products, and epsilon-PL production was further increased to 62.36 g L-1 at 192 h, compared to 54.70 g L-1 of the control without supplementary talc. This is also the highest epsilon-PL production reported so far in the literature. These results suggested that talc addition could be an efficient and universal approach for enhancing 3-PL production in industry.