Enhanced production of nukacin D13E in Lactococcus lactis NZ9000 by the additional expression of immunity genes
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Nukacin D13E (D13E) is a variant of type-A(II) lantibiotic nukacin ISK-1 produced by Staphylococcus warneri ISK-1. D13E exhibited a twofold higher specific antimicrobial activity than nukacin ISK-1 against a number of Gram-positive bacteria. We previously reported the heterologous production of D13E in Lactococcus lactis NZ9000 under the control of nisin-controlled gene expression system. In this study, we demonstrated enhanced production of D13E by the additional expression of immunity genes, nukFEG. The nukacin ISK-1 immunity, conferred by the ABC transporter complex, NukFEG, and the lantibiotic-binding protein, NukH, was not overwhelmed by D13E. The additional NukFEG resulted in a fourfold increase in the immunity level of the strain and a 5.2-fold increase in D13E production. The additional NukFEGH-expressing strain with the highest D13E immunity showed reduced level of production. Further improvement in D13E production was achieved by using pH-controlled batch fermentation.
KeywordsLantibiotic Nukacin ISK-1 Nisin-controlled gene expression Immunity genes Fermentation
The authors would like to thank Dr. Shun Iwatani for his helpful suggestions. This work was partially supported by grants from the following organizations: the Japan Society for the Promotion of Science (JSPS), the Japan Science Society, the Novartis Foundation (Japan) for the Promotion of Science, the Novozymes Japan Research Fund, and the Nagase Science and Technology Foundation.
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