[Continuous production of nisin by calcium alginate-immobilized Lactococcus lactis subsp. lacits SM526]

The attempts were made to produce nisin by immobilized cells of Lactococcus lactis subsp. lactis SM526 entrapped in calcium alginate beads. The results showed that the immobilized cell beads were intact for 90 hr under 2% of calcium alginate in 10 mmol/L CaCl2 solution. The physical stability of beads was improved by removing phosphate, citrate and acetate salts supplied in SYS3 medium. Repeated-batch fermentation utilizing immobilized cells were performed in mSYS3 medium without agitation at 32 degrees C, the concentration of nisin produced during the third cycles increased to 850 IU/mL, and the beads were still intact with little cell leakage. The immobilized beads were loaded into a sterilized glass column to continuous fermentation, nisin concentration increased to 1150 IU/mL, as high as that obtained in free-cell fermentation, and the high productivity was stable for up to 70 h under a constant supplied of the fresh mSYS3 medium.