Abstract:

Our previous study has shown that the culture supernatant of Stenotrophomonas maltophilia can effectively degrade aflatoxin B1 (AFB1). In this study, the Stenotrophomonas maltophilia NMO-3 preserved in our lab was selected to degrade AFB1, and the fermentation medium and conditions of the strain were optimized to achieve the highest degradation rate of aflatoxin B1. Fructose, tryptone and Mg2+ (MgCl) were selected as the optimum carbon source, nitrogen source and metal ion for the fermentation of Stenotrophomonas maltophilia NMO-3 by one-factor-at-a-time method, and their optimal addition amounts were optimized by quadratic regression orthogonal design. In addition, five fermentation conditions such as initial pH of medium, inoculation amount, temperature and medium volume filled into 300-ml erlenmeyer flask were also optimized by one-factor-at-a-time method. The results showed that the optimal medium contained 1.0% fructose, 1.0% tryptone and 0.05 mmol/L magnesium chloride, and the optimum fermentation conditions were as follows: pH 7.5; temperature, 35 ℃; seed age, 12 h; inoculation amount, 5% (V/V); medium volume filled into 300-ml erlenmeyer flask, 25 ml; shaking speed, 140 r/min; and fermentation cycle, 24 h. After the mixture of 800 μl of the culture supernatant obtained under the optimized conditions and 200 μl of 500 μg/ml AFB1 solution was left to incubate for 72 h at 35 ℃, the degradation rate of AFB1 attained the maximum value, 94.29%.

Key words: AFB1, fermentation culture, fermentation condition, optimization