| Nisin is the primary metabolites of Streptococcus lactis and a kind of natural food preservative which could inhibit the growth of G+ bacteria and is widely used in food industry.In this paper, Streptococcus lactis 6032 was adopted to produce Nisin by resin adsorption fermentation couping with separation to relieve the feedback inhibition of Nisin and improve the yield of nisin. The experimental results are as follows.Compared with the growth curve of Streptococcus lactis 6032 and Nisin production, the results showed that the growth of Streptococcus lactis and Nisin production is synchronous. Single factor experiments indicated that the highest Nisin titer was up to 4955.45 IU/m L, when temperature was 29 ℃, inoculation quantity was 5% and the amount of corn steep liquor was 25%. The Box-Behnken response surface experiment indicated that the best fermentation conditions were temperature 29.18 ℃, inoculation quantity 5.02%, the amount of corn syrup 27.09%, the highest Nisin titer was 4991.64 IU/m L.Macroporous adsorption resin D101, NKA-II and ion exchange resin D113,D151 adsorbed Nisin of fermentation broth and their adsorption rates were respectively 34.83%, 69.80%, 63.19% and 56.35%. The results showed that the adsorption rate of NKA- II and D113 was higher and their best adsorption conditions were fermentation broth volume 70 m L and 60 m L, adsorption time 5h, fermentation broth p H4 and p H5, rotate speed 110 r/min and 100 r/min, their adsorption rates were respectively 67% and 72%. The results of the desorption of ethanol(p H2) and Na Cl solution for the NKA-II resin and D113 resin showed that, their desorption rates were 44% and 47%, when the concentration was 80%and 5%, the volume of desorption solution was 70 m L and 80 m L, the desorption time was 7 h and 8 h.The results of NKA-II and D113 adsorption fermentation coupling with separation to produce Nisin in static state showed that NKA-II and D113 didn’t have adverse effect on cell growth. The best conditions of NKA-II and D113 resin adsorption fermentation coupling with separation to product Nisin were p H5.5 and p H6, the amount of resin of 1.5 g and 1.0 g, resin added time 6th h and 5.5th h, the rotate speed of 80 r/min, their Nisin titer were 5641.57 IU/m L and 5663.92 IU/m L. The results of the desorption of ethanol(p H2) and Na Cl solution for the NKA-II resin and D113 resin showed that,their desorption rates were 47% and 45%, when the concentration was 80% and 5%, the desorption time was 7 h and 8 h and desorption solution volume was 100 m L and 90 m L.The results of D113 resin adsorption fermentation coupling with separation to produce Nisin showed that fermentation broth can be recycled at the circulating system and the process of D113 resin adsorption fermentation coupling with separation to produce Nisin is feasible. Single factor experiments indicated that Nisin titer was 5889.50 IU/m L, when the height of resin was 7 cm,flow rate was 200 m L/h, the beginning adsorption time of resin was 5th h. The Box-Behnken response surface experiment indicated that the highest nisin titer was up to 6333.57 IU/m L, when the height resin was 7.11 cm, flow rate was200.89 m L/h and the beginning adsorption time of resin was 5.01 th h. Through this circulating system, the fermentation of coupling with separation can be conducted which relieve feedback inhibition of Nisin and was a good way to improve the yield of Nisin. Nisin of the fermentation broth is detected by SEM and HPLC. The result of SEM showed that the shape structure of Nisin of the fermentation broth and Nisin standard was same, the result of HPLC showed that there was same characteristic peak at the time for Nisin of the fermentation broth and Nisin standard, it is indicated that the fermentation broth contains Nisin. |
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