Astragalus of traditional Chinese medicine (TCM) and Bacillus subtilis are extensively used in animal feed and for production of various fermented compounds. In order to observe the characteristics of HNMY-13 and HNMY-15 B. subtilis strains, this study focused on the optimization of parameters in liquid fermentation of the two strains in aflatoxin B1 degradation, and Astragalus polysaccharide yield. The optimal parameters: degradation of aflatoxin B1, the bacterial count, and the Astragalus polysaccharide yield analysis were examined in this study. It was shown that the percentage degradation of AFB1 by HNMY-13 and HNMY-15 strains were 80.48 and 79.55% at 37°C, and 80.66% and 81.34 with pH 7.0. The percentage degradation by HNMY-13 was 88.07% after 48 h fermentation and by HNMY-15 was 84.81% after 60 h fermentation, respectively. The viable count of fermented sample was 8.8×108 and 7.6×108 CFU·mL-1 using HNMY-13 and HNMY-15 strains, respectively. The polysaccharide yielded by HNMY-13 was 4.93% at 48 h which is 1.7-fold higher than that of the control group, while polysaccharide yielded by HNMY-15 reached peak of 3.54% at 60 h. In conclusion, HNMY-13 and HNMY-15 of B. subtilis promote production of Astragalus polysaccharide in the process of liquid fermentation and can also degrade aflatoxin B1 significantly; hence the combination could form a potential feed additive for animals.
Key words: Astragalus, Bacillus subtilis, liquid fermentation, aflatoxin B1, polysaccharide.
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