Study On Industrialized Process In Microbial Fermentation Of Nisin

Nisin,which is a type of natural food antiseptic,produced by microbial fermentation.Nisin has been researched for a long time in our country,but until recently most of the researches are under static culture In this paper,according to the properties of nisin,methord of measurement of nisin concentration in broth was ameliorated,medium of fermentation was ameliorated,Condition of fermention was optimized,industrial medium substituted for reagent medium,process of separation and purification of fermented liquor was studied.1. Methord of measurement of nisin concentration.The conditions of agar diffusion technique measurement nisin potency were studied.It is very important step to measure nisin potency for the fermentation industrialization of nisin.There are many impressing factors in the determining course,for two dosage technique,only the differents of product and sample have efficient effects on nisin potency.In this way, the determination of nisin potency was simplified.A computer program was designed to calculate the data obtained.This program directly makes use of formula of two dosage technique to calculate potency.2. Amelioration of fermentation medium. Optimum medium of fermentation of Streptococcus lactis is(g/ 100ml):saccharose 4,yeast extract 1,peptone 0.5,CSL 5,dihydric phosphate 2,magnesium sulfate 0.02,sodium chloride 0.2.Applied this medium,potency of fermented liquor can level off 6000~7000IU/ml.This fermentation medium reduced dosage of hydronitrogen by increase dosage of saccharose.Cost of production was corresponded to reduce.3. Optimization of fermentation conditions. Semi-batching the liquid of 5mol/L soda-lye during the fermentation and controling the pH value in the range of 6.20-6.25 while Lactococcus lactis come into being nisin,so that we can prolong the time of fermentation and increase the production of nisin. Synthetized the factors of potency and inoculant, initialization pH of fermented liquor is 7.8, temperature of fermentation is 30℃, inoculant is 5%~6%,in these condition, output of nisin was maximized. A mathematical kinetic models of determining the terminal point was founded,so that inactuvation of nisin can be avioded when it reaches the terminal point.4. Substitution of industrial medium. Contrasted the reagent with the industrial medium, optimum industrial medium was confirmed,which is (g/100ml)saccharose 4, yeast extract 1,peptone 1, CSL 5,dihydric phosphate 2,magnesium sulfate 0.02,sodium chloride 0.2.Applied this industrial medium,potency of fermented liquor can level off 6000IU/ml. Contrasted reagent medium,potency reduced about 10%,but cost of production reduced to 61%.5. Process of isolation and purification of nisin. Optimum conditions of predisposal are: pH 2.5,temperature 90°C,heating time 20min. Pressure of membrane separation is 0.10MPa. Yield of membrane separation is 67%. Optimum conditions of salting-out are:pH 3.5, dosage of ammonium sulfate 25g/100ml,time of salting-out lh.Under rev 28000rad/min and flux 15L/h, Yield of centrifugal separation reached to 90%.By this separate process,yield of nisin overrun 60%.