铜绿假单胞菌M4菌株降解黄曲霉毒素B_(1)的条件优化研究

Optimization of conditions for degradation of aflatoxin B_(1) by Pseudomonas aeruginosa M4 strain

为了提高筛选菌株对黄曲霉毒素B_(1)(aflatoxin B_(1),AFB_(1))的降解效率,以铜绿假单胞菌M4(Pseudomonas aeruginosa)为研究对象,对其发酵和降解条件进行优化。结果表明:初始p H值、发酵温度和发酵时间对菌株生长及AFB_(1)降解率具有显著影响。进一步通过Box-Behnken设计进行响应面优化试验,以AFB_(1)降解率为响应值确定最佳发酵条件:初始pH 6.80、发酵温度36.0℃、发酵时间56.0 h。降解温度显著影响发酵上清液对AFB_(1)的降解,95℃处理6 h后,AFB_(1)降解率达到96.17%;Fe^(3+)、Mg^(2+)和Zn^(2+)等金属离子显著抑制发酵上清液对AFB_(1)的降解,Cu^(2+)和Mn^(2+)离子对AFB_(1)降解过程具有促进作用。经优化后的发酵上清液对AFB_(1)降解率由34.10%升高至96.17%,显著提高了降解效率,为该降解菌在食品和饲料行业中的应用提供了理论依据。

Aflatoxin B_(1)(AFB_(1))is one of the most carcinogenic chemicals,posing a serious threat to the food and feed industries.In this study,the fermentation and degradation conditions by Pseudomonas aeruginosa M4 were optimized to improve the degradation efficiency on AFB_(1).Single factor test was applied based on the evaluation index of strain grow th and AFB_(1) degradation rate.The results showed that the conditions of inoculum volume of 5%,liquid volume of 25 mL/250 mL,initial p H value of 7.0,fermentation temperature of 37℃and fermentation time of 48 h are conducive to the degradation of AFB_(1),and the degradation rate of AFB_(1) increased to 47.65%.The response surface optimization experiment was carried out by Box-Behnken design.The initial pH value,fermentation temperature and fermentation time were used as the response variables,and the AFB_(1) degradation rate was set as the response value.The optimal fermentation conditions are as follow s:the initial p H value was 6.80,the fermentation temperature was36.0℃,and fermentation time was 56.0 h.The highest degradation rate of AFB_(1) was 52.84%,which was not significantly different from the predicted value(P>0.05).The effect of degradation conditions on the degradation of AFB_(1) by fermentation supernatant was studied,and the results showed that the degradation temperature significantly affected the degradation rate of AFB_(1).In the temperature range of 30-60℃,the degradation rate of AFB_(1) increased with the increase of the fermentation temperature.At the same degradation temperature,with the extension of degradation time,the degradation rate of AFB_(1) gradually increased and then tended to be stable.After 6 hours of degradation at 95℃,the degradation rate reached96.17%,which was much higher than the degradation rate before optimization.In addition,0.01 mol/L Fe^(3+),Mg^(2+)and Zn^(2+)metal ions can significantly inhibit the degradation process of AFB_(1),and Fe^(3+)had the most significant inhibitory effect,reducing the degradation rate of AFB_(1) from 93.85%to 20.85%.However,Cu^(2+)and Mn^(2+)ions promoted the degradation of AFB_(1).In this study,the optimized fermentation condition significantly increased the degradation rate of AFB_(1) from 34.10%to 96.17%,and this study provided a theoretical basis for the application of the degrading bacteria in the food and feed industries.