Fermentation Technology Suitable To Industrial Production By Using A High-yield Nisin Strain

Nisin is one of the natural food preservatives which are internationally allowed into its commercial production.In order to decrease the nisin production cost,in this paper the fermentation conditions of a nisin high-yield strains,which was with a high culture medium cost and a long fermentation time,was studied for its apply to the industrialized production.Firstly,the culture mediums of laboratory test fermentation and industrialized production fermentation were integrated,then a culture medium was got and it maked the fermentation time,culture medium cost and nisin production of the nisin high-yield strains was satisfactory;Subsequently,the fermentation technology by using partial substitution of glucose for sucrose was put forward to further decrease the production cost of nisin;Finally,the two-stage pH controlled technology was put forward to further increase the nisin production.In this work,the culture medium from experiments was made of 30 g of sucrose,3 g of yeast extract,6 g of peptone,1.5 g of yeast powder,2 g of Na2HPO4,1.5 g of MgSO4·7H2O and 25 g of corn steep liquor per liter of distilled water.On the premise of the fermentation time within 20 hour,compared with the the culture mediums of laboratory test fermentation,the nisin titer increased 7.6 percent and the culture medium cost decreased 46.6 percent;compared with the culture mediums of industrialized production fermentation,the nisin titer increased 47.4 percent and the culture medium cost decreased 3.5 percent.By studying the effects of glucose,sucrose and their synergy on cell growth,nisin titer and NaOH aqueous solution dosage,the novel fermentation technology,in which sucrose was used as substrate carbon source and glucose was used as adding carbon source,were put forward.The suitable technology of the novel fermentation technology was that in the fermentation broth of 500 mL sucrose concentration of 15 g/L was used as substrate carbon source and the concentration of glucose,which was added into the fermentation broth with the NaOH aqueous solution dosage from the 4th hour,was 15 g/L.The nisin titer of the novel fermentation technology was 5256 IU/mL,which was similar to the nisin titer of the fermentation of using sucrose as carbon source and the cost of carbon source decreased 25.9 percent.By studying the effect of the controlled pH(5.6?5.8?6.0?6.2?6.4)on the cell growth and the nisin titer,the two-stage pH controlled technology,which the pH value was controlled to be a high value in the initial stage of fermentation then a low value in the later stage,was put forward.Then the RSM was used to get the optimum operating conditions of the two-stage pH controlled method that the stage-1 pH of 6.42?the pH different between the two stages of 0.66 and the pH change time of the 9.95 th hour,under these operation conditions,the nisin titer reached to 5898 IU/mL,which was 925 IU/mL bigger than that of the pH controlled experiment,the nisin titer showed a 18.60 percent increase.The above results indicated that the culture medium and the fermentation technologies,which were put forward by this work,could decrease the fermentation time,decrease the culture medium cost and increase the nisin titer.Thus it can be seen that these studies could significantly decrease the production cost of nisin and promote the application of nisin in food industry.