Department of Analytical and Food Chemistry, Food Science and Technology Faculty, Ourense campus, University of Vigo, Ourense Campus, As Lagoas s/n, 32004, Ourense, Spain.
Appl Microbiol Biotechnol. 2016 Sep;100(18):7899-908. doi: 10.1007/s00253-016-7558-9. Epub 2016 Apr 25.
Nisin production by Lactococcus lactis CECT 539 was followed in batch cultures in whey supplemented with different concentrations of glucose and in two realkalized fed-batch fermentations in unsupplemented whey, which were fed, respectively, with concentrated solutions of lactose and glucose. In the batch fermentations, supplementation of whey with glucose inhibited both the growth and bacteriocin production. However, fed-batch cultures were characterized with high productions of biomass (1.34 and 1.51 g l(-1)) and nisin (50.6 and 60.3 BU ml(-1)) in comparison to the batch fermentations in unsupplemented whey (0.48 g l(-1) and 22.5 BU ml(-1)) and MRS broth (1.59 g l(-1) and 50.0 BU ml(-1)). In the two realkalized fed-batch fermentations, the increase in bacteriocin production parallels both the biomass production and pH drop generated in each realkalization and feeding cycle, suggesting that nisin was synthesized as a pH-dependent primary metabolite. A shift from homolactic to heterolactic fermentation was observed at the 108 h of incubation, and other metabolites (acetic acid and butane-2,3-diol) in addition to lactic acid accumulated in the medium. On the other hand, the feeding with glucose improved the efficiencies in glucose, nitrogen, and phosphorus consumption as compared to the batch cultures. The realkalized fed-batch fermentations showed to be an effective strategy to enhance nisin production in whey by using an appropriate feeding strategy to avoid the substrate inhibition.
乳链菌肽由 Lactococcus lactis CECT 539 在添加不同浓度葡萄糖的乳清补料分批培养中进行生产，在未添加乳清的两种再碱化补料分批发酵中进行生产，分别用乳糖和葡萄糖的浓缩溶液进行补料。在分批发酵中，乳清中葡萄糖的添加抑制了生长和细菌素的产生。然而，与未添加乳清的分批发酵（0.48 g l(-1)和 22.5 BU ml(-1))和 MRS 肉汤（1.59 g l(-1)和 50.0 BU ml(-1))相比，补料分批培养的生物量（1.34 和 1.51 g l(-1))和乳链菌肽（50.6 和 60.3 BU ml(-1))产量较高。在两种再碱化补料分批发酵中，细菌素产量的增加与每个再碱化和补料循环中产生的生物量和 pH 值下降平行，表明乳链菌肽是作为一种依赖 pH 值的初级代谢物合成的。在孵育 108 小时时，观察到从同型乳酸发酵到异型乳酸发酵的转变，除了乳酸外，培养基中还积累了其他代谢物（乙酸和丁烷-2,3-二醇）。另一方面，与分批培养相比，葡萄糖的补料提高了葡萄糖、氮和磷的消耗效率。再碱化补料分批发酵是一种有效的策略，通过使用适当的补料策略来避免基质抑制，从而提高乳清中乳链菌肽的生产。
