Study on the process of fermentation coupling with foam fractionation and membrane module for nisin production

Nisin, an antimicrobial peptide, is commercially used as a food preservative and a promising alternative in medical applications for inhibiting bacterial infection in both humans and livestock. It is produced by fermentation using certain strains of Lactococcus lactis ssp. lactis. In traditional fermentation, the yield of nisin has always been limited by adsorption of nisin onto its producer, enzymatic degradation and product inhibition. This limitation can be solved by fast removal of the product from the broth during fermentation. In the current work, a technology of fermentation coupling with foam fractionation and membrane module was developed to achieve in situ removal of nisin produced by L. lactis ssp. lactis ATCC 11454 from the broth. The effects of air flow rate, the initial aeration time and interval time on the performance of the technology were studied to increase the yield of nisin. The results showed that under the optimal conditions of air flow rate 60 mL/min, the initial aeration time of the fourth hour and regular 30-min interval, the total nisin titer reached 3946 IU/mL, increased by 24.2%, compared with the control group (3177 IU/mL). Therefore the coupling technology can effectively weaken the feedback inhibition and thus increase the yield of nisin by in situ fast removal of the product from broth during fermentation. (C) 2014 Curtin University of Technology and John Wiley & Sons, Ltd.