Improvement of [epsilon]-Poly-l-Lysine Production Through Seed Stage Development Based on In Situ pH Monitoring

• Published in: Applied biochemistry and biotechnology 2015-01, Vol.175 (2), p.802
• Main Authors: Sun, Qi-xing, Chen, Xu-sheng, Ren, Xi-dong, Mao, Zhong-gui
• Format: Article
• Language: English
• Subjects: Bacteria; Biotechnology; Fermentation; Food preservation; Glycerol; Industrial production; Preservatives
• ISSN: 0273-2289; 1559-0291
• DOI: 10.1007/s12010-014-1329-9

Nissin, natamycin, and [straight epsilon]-poly-l-lysine ([straight epsilon]-PL) are three safe, microbial-produced food preservatives used today in the food industry. However, current industrial production of [straight epsilon]-PL is only performed in several countries. In order to realize large-scale [straight epsilon]-PL production by fermentation, the effects of seed stage on cell growth and [straight epsilon]-PL production were investigated by monitoring of pH in situ in a 5-L laboratory-scale fermenter. A significant increase in [straight epsilon]-PL production in fed-batch fermentation by Streptomyces sp. M-Z18 was achieved, at 48.9 g/L, through the optimization of several factors associated with seed stage, including spore pretreatment, inoculum age, and inoculum level. Compared with conventional fermentation approaches using 24-h-old shake-flask seed broth as inoculum, the maximum [straight epsilon]-PL concentration and productivity were enhanced by 32.3 and 36.6 %, respectively. The effect of optimized inoculum conditions on [straight epsilon]-PL production on a large scale was evaluated using a 50-L pilot-scale fermenter, attaining a maximum [straight epsilon]-PL production of 36.22 g/L in fed-batch fermentation, constituting the first report of [straight epsilon]-PL production at pilot scale. These results will be helpful for efficient [straight epsilon]-PL production by Streptomyces at pilot and plant scales.