title: [Enhanced nisin production by overexpression of nisin immunity gene nisI in the nisin-producing strain].
abstract: OBJECTIVE
  Our aim was to enhance nisin production by overexpression of nisin immunity gene nisI in nisin-producing strains.
  
  
  METHODS
  Nisin immunity gene nisI with a strong promoter P59 was cloned into vector pHJ201 and introduced into Lacotococcus lactis NZ9800, resulting in a recombinant strain L. lactis NZ9800/pHMI. Then the differences between the recombinant strain and the control strain L. lactis NZ9800/pHJ201 were analyzed in several aspects, including their growth curves, nisin resistance level and antibacterial activity against indicator strain Microccus flavus NCIB 8166.
  
  
  RESULTS
  The overexpression of nisI had no significant difference in growth rate between recombinant strain and contrast strain. However, it promoted recombinant strain tolerance 25% higer nisin resistance level and stronger antibacterial activity against M. flavus NCIB 8166, which was increased by 32% and 25% when fermented for 6 and 8 hours, respectively.
  
  
  CONCLUSIONS
  These results indicated that overexpression of nisI gene in the nisin producing strain can effectively enhance nisin resistence level and thus improve nisin production.
authors.affiliation: College of Life Science, Anhui Agricultural University, Hefei 230036, China. huhongmei169@yahoo.com.cn
authors.forename: Hongmei
authors.initials: H
authors.lastname: Hu
authors.forename: Like
authors.initials: L
authors.lastname: Jiang
authors.forename: Yuheng
authors.initials: Y
authors.lastname: Lin
authors.forename: Liandong
authors.initials: L
authors.lastname: Huan
authors.forename: Jin
authors.initials: J
authors.lastname: Zhong
mesh_terms: D000900:Anti-Bacterial Agents / Q000096:biosynthesis / Q000494:pharmacology*; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects* / Q000276:immunology; D007109:Immunity / Q000187:drug effects*; D013294:Lactococcus lactis / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D009561:Nisin / Q000096:biosynthesis* / Q000494:pharmacology; D009876:Operon; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D000900:Anti-Bacterial Agents; D009561:Nisin