【摘要】 【目的】通过基因工程手段增加乳链菌肽(nisin)自身免疫基因nisI在nisin产生菌Lactococcus lactisNZ9800/pHJ201中的表达水平,增强该菌对nisin的抗性,从而达到提高nisin产量的目的。【方法】将带有强组成型启动子P59的免疫基因nisI克隆到nisin表达质粒pHJ201上,将重组质粒引入L.lactis NZ9800中,使nisI基因过量表达,得到重组菌株L.lactis NZ9800/pHMI,并比较该重组菌株与对照菌株L.lactis NZ9800/pHJ201的生长曲线、对nisin的抗性水平、抑菌活性及nisin产量的差异。【结果】nisI的表达对重组菌的生长速度没有明显的影响,却能促使重组菌株对nisin的抗性水平提高25%、在发酵6h和8h时,nisin的产量分别提高32%和25%。【结论】增加乳链菌肽自身免疫基因nisI的表达可以提高产生菌对nisin的抗性,从而提高乳链菌肽产量。更多还原

【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.[Conclusion] These results indicated that overexpression of nisI gene in the nisin producing strain can effectively enhance nisin resistence level and thus improve nisin production.更多还原