Online recovery of nisin during fermentation coupling with foam fractionation

•To reduce product inhibition, online recovery of nisin during fermentation was tested.•Two technologies of fermentation coupling with foam fractionation were tested.•Sterile air and nitrogen were individually bubbled into the broth.•Nisin activity was improved by 36.2% compared with traditional process.

Online foam fractionation was proposed for recovering nisin during the fermentation of Lactococcus lactis subsp. Lactis ATCC 11454. Two strategies of fermentation coupling with foam fractionation were designed. In each strategy, sterile air and nitrogen were individually bubbled into the broth. The results showed that the activity of nisin in both continued to increase after the completion of the foam fractionation process. The maximum total nisin activity (4657 IU/mL) was achieved when online foam fractionation was carried out using sterile air of 30 mL/min between 6 h and 12 h, which was improved by 36.2% compared with that of the traditional batch fermentation (3420 IU/mL) without online separation. This improvement is mainly attributed to the relief of product inhibition through online recovery of nisin, which demonstrates a promising process of industrial nisin production.