Influence of growth conditions on the nisin production of bioengineered Lactococcus lactis strains

Abstract

Nisin production of three bioengineered strains, (LAC338, LAC339 and LAC340) with immunity (nisFEG) and/or regulation (nisRK) genes of nisin biosynthesis on plasmids in the Lactococcus lactis LL27 nisin producer, was evaluated under pH-controlled and pH-uncontrolled batch fermentations. Optimization studies showed that fructose and yeast extract yielded the highest nisin activity. The strains LAC338, LAC339, and LAC340 produced 24, 45, and 44% more nisin, respectively, than wild-type L. lactis LL27 after 12-h incubation. However, sharp decreases in the yield of nisin were observed at the late phase of fermentation with LAC339 and LL27 in contrast to LAC340 and LAC338 strains for which the high level of nisin could be maintained longer. Obviously, increasing the copy number of the regulation genes together with immunity genes in the nisin producers retarded the loss of nisin in the late phase of the fermentation.

Enhance nisin yield via improving acid-tolerant capability of Lactococcus lactis F44

“…lactis A164, additional copies of nisin self-protection (immunity) genes nisFEG and the regulatory genes nisRK with high copy number plasmid in the producer strain enhanced the 1.5–1.7-fold higher than the nisin yield of the original strain9. Also in another study, provision of additional copies by cloning nisRK and/or nisFEG genes on plasmids in the L. lactis LL27 resulted in producing 45%, 24% and 44% more nisin compared to the original yield 520 IU/mL, respectively10. Furthermore, the bioactive recombinant nisin of the nisin deficient strain L. lactis MG1363 were overproduced with a yield of 1098 IU/mL when additional copies of an entire nisin biosynthesis pathway were present11.…”

Continuous nisin production with bioengineered Lactococcus lactis strains

“…In the current study, at a 0.2 h -1 dilution rate, it was determined that strains produced their maximum nisin amount by consuming on average 4.48 g fructose per biomass unit per hour, which is in the range of data obtained using other carbon sources [16,18,22]. However, higher specific nisin productivities with the recombinant strains than wild-type LL27 for all tested fructose concentrations proved that, in continuous culture, fructose concentration had no effect on the nisin production of recombinant strains (Fig.…”

Optimisation of bacteriocin production of Lactococcus lactis subsp. lactis MA23, a strain isolated from Boza

“…The samples were collected from the fermentor after 3, 5, 8, 10 and 12 h. Cell density (OD 600 ) was measured and bacteriocin production amount was determined in AU per millilitre (Ryan et al. 1996; Şimşek et al. 2009).…”