稀土盐与泡沫分离强化乳酸乳球菌生产乳链菌肽

Promotion of Nisin production by Lactococcus lactis through adding rare earth salt and performing foam fractionation

乳链菌肽(Nisin)是一种重要的食品防腐剂,但其工业应用却受限于较低的生产效率。该研究拟采用稀土盐和泡沫分离强化乳酸乳球菌生产Nisin。利用摇瓶试验研究了8种稀土盐对菌体生长和Nisin生物合成的影响。以Nisin的回收率和发酵液的总Nisin效价为指标,利用单因素试验和响应面优化试验获得了发酵与泡沫分离耦合操作的最佳工艺条件。结果表明,所选的8种稀土盐中,添加氯化铥(TmCl_(3))至发酵培养基能够大幅增加菌体生物量和Nisin产量。在发酵9 h添加1×10^(-4)mol/L的TmCl_(3),发酵液的Nisin效价达到(5643.23±156.57)IU/mL。在发酵与泡沫分离初始耦合时间18.50 h,气体分布器孔径300μm和气体体积流率135 mL/min条件下,Nisin的回收率和发酵液的总Nisin效价分别为(89.43±2.35)%和(6159.00±89.35)IU/mL。综上,适量添加稀土盐和执行泡沫分离,能够在促进菌体生长的同时缓解产物抑制,实现Nisin的高效生产。该研究提出的外源辅因子刺激和产物原位分离方法对于强化Nisin的工业生产具有重要意义。

Nisin is an important food preservative but its industrial utilization is limited by the low production efficiency.This work attempted to promote Nisin production by Lactococcus lactis through adding rare earth salt and performing foam fractionation.Flask-shaking tests had been conducted to investigate the effects of eight rare earth salts on strain growth and Nisin biosynthesis.With the recovery percentage of Nisin and the total Nisin titer of fermentation broth as the indexes,the optimal conditions of fermentation-foam fractionation coupling operation were obtained by using single factor test and response surface optimization test.Results indicated that among the selected eight rare earth elements,cell biomass and Nisin production could be dramatically enhanced by adding TmCl_(3)into fermentation medium.When adding time of TmCl_(3)was 9 h,the Nisin titer of fermentation broth was as high as(5643.23±156.57)IU/mL.Under the conditions of initial coupling time of fermentation and foam fractionation 18.50 h,pore diameter of gas distributor 300μm and volumetric air flow rate 135 mL/min,the recovery percentage of Nisin and total Nisin titer of fermentation broth were(89.43±2.35)%and(6159.00±89.35)IU/mL,respectively.To sum up,it was conducive to achieving the efficient production of Nisin by moderately adding rare earth salt and performing foam fractionation,which could promote strain growth and mitigate product inhibition,simultaneously.In this work,the strategies of exogenous cofactor stimulation and in-situ product separation were of great significance to promoting the industrial production of Nisin.