Strengthening Nisin Production by Using the Coupling Technology of Foam Fractionation and Microcapsule Cells Immobilizing Two Strains Fermentation

This work was aimed at strengthening Nisin production by coupling foam fractionation with microcapsule cells fermentation, in which Lactococcus lactis subsp.lactis (L.lactis) and Saccharomyces cerevisiae (S.cerevisiae) were co-cultivated to relieve the product inhibition from lactic acid. The concentrations of sodium alginate and chitosan were optimized to prepare liquid-core microcapsules for immobilizing L.lactis and S.cerevisiae. Results indicated that the Nisin titer in co-cultivation fermentation broth was as high as 3436.3 IU/mL by using lactose as carbon source and setting initial inoculation ratio of L.lactis and S.cerevisiae at 10²:1. The optimal preparation conditions of sodium alginate/chitosan/sodium alginate (ACA) liquid-core microcapsules were sodium alginate concentration of 15 g/L and chitosan concentration of 5.5 g/L. Under the suitable conditions of foam fractionation coupled with microcapsule cells fermentation after cultivation for 21 h, pore diameter of gas distributor 180 μm and volumetric air flow rate 40 mL/min, the enrichment ration and recovery percentage of Nisin reached 5.8 and 63.1%, respectively. The total yield of Nisin in fermentation broth was 3973.2 IU/mL. The coupling technology of microcapsule cells immobilizing two strains fermentation and foam fractionation could effectively overcome the obstacles of product inhibition and strain cell loss, thus facilitating the high-density and continuous fermentation for Nisin production.