OPTIMIZATION OF FERMENTATION PROCESS OF KLEBSIELLA SP.XY1 FOR DEGRADING AFLATOXIN B₁

In this study,fermentation process of aflatoxin B₁(AFB₁) degradation strain Klebsiella sp.XY1 preserved in our lab was optimized.The optimization of fermentation process consisted the fermentation medium and conditionsincluding carbon source (glucose,soluble starch,corncob,α-Lactose,D-Fructose,sucrose,mannitol),nitrogen source (yeastextract,beefextract,peptone,tryptone,urea,ammonium nitrate,sodium nitrate) and metal ion (CaCl₂,MgCl₂,FeCl₂,ZnSO₄,CuSO₄,MnCl₂).Additionally,the fermentation conditions including initial pH,temperature,inoculation and medium volume were also optimized.Based on single-factor experiment,the best carbon source,nitrogen source and metal ion were confirmed.According to the single factor test results,response surface test using the principle of Box-Behnken was designed to optimize the degradation conditions.The results of variance analysis showed that the response surface model (P=0.001 4) was significant at the 1% level and lack of fit was not significant (P=0.065 2>0.05).R ²=0.943 1,R ²_Adj=0.870 1,indicating that the model fitting degree was suitable to simulate the change of AFB₁degradation rate of 94.31%,wherein the effect of corncob on the degradation rate of AFB₁was most significant.The results indicated that the optimal medium contained 1.06% corncob,1.32% tryptone and 0.036 mol/L calcium chloride.The optimum fermentation conditions were as follows:initial pH 7.0,temperature 34℃,inoculation amount 6%(V/V),medium volume 25 mL in a 250 mL erlenmeyer flask.After optimization of the fermentation process,the degradation rate of AFB₁increased from 71.91% to 95.13%.