AFB1降解菌的分离鉴定、降解条件优化及降解产物毒性评估

【目的】从土壤样品中筛选能降解黄曲霉毒素B（ 1 Aflatoxin B₁，AFB₁）的菌株，并研究其对AFB₁的降解性质及抑制黄曲霉菌能力，评估其作为微生物降解AFB₁制剂的潜力，为进一步开发AFB₁脱毒剂提供参考依据。【方法】以香豆素为唯一碳源，筛选出1株高效的AFB₁降解菌，通过16S rRNA基因测序得知菌株所属种属，并利用高效液相色谱确定菌株降解AFB₁的特性，通过单因素试验优化该菌株降解AFB₁的效率，共培养分析其对黄曲霉菌的抑制作用，最后利用SOS显色反应评估菌株对AFB₁的脱毒效果。【结果】通过液相色谱检测，获得1株菌株GDAAS003对AFB₁的降解率相对较高，其16s rRNA基因序列与链霉菌Streptomyces cerasinus SR3-134（LC128347.1）的相似性高达100%，菌株降解AFB₁的活性物质主要存在于上清液中，可能为胞外酶。GDAAS003上清液降解AFB₁的最佳pH为8.0的磷酸盐缓冲液，最适反应温度为30℃。经优化，菌株GDAAS003上清液对50 ng/mL AFB₁ 96 h的降解率可达90.50%，对100 ng/mL AFB₁ 96 h的降解率为75.68%。对降解产物的遗传毒性进行检测，结果表明菌株GDAAS003降解AFB₁的产物未表现出毒性，同时GDAAS003能抑制玉米中黄曲霉菌合成AFB₁。【结论】链霉菌GDAAS003既能以较高的降解效率降解AFB₁，又能抑制黄曲霉菌的生长，其在食品和饲料行业中有较大的商业应用前景。

AFB1 degrading bacteria:Isolation,identification,optimization of its degradation conditions and toxicity evaluation of its degradation products

【Objective】 In order to solve the problem of aflatoxin B₁(AFB₁)contamination in feed and food, an AFB₁- degrading strain was screened from soil samples and its capacities for degradation of AFB₁ and inhibition of Aspergillus flavus growth were studied.【Method】 Using coumarin as the sole carbon source, an efficient AFB₁ degrading strain was selected. The species of the strain were identified by 16S rRNA gene sequencing and its degradation characteristics of AFB₁ were studied by High performance liquid chromatography(HPLC). The degradation efficiency of GDAAS003 on AFB₁ was optimized by single factor experiment, and the inhibition effect of GDAAS003 on A. flavus growth was analyzed by co-culture. Finally, the SOS-Chromotest was used to evaluate the detoxification of AFB₁ by the strain.【Result】Through HPLC detection, a highly efficient AFB₁-degrading strain was selected. 16S rRNA analysis showed that the sequence of GDAAS003 was 100% homologous to that of Streptomyces cerasinus SR3-134(LC128347.1), and that the AFB₁ degradation activity was extracellular and enzymatic. The results showed that the optimum pH of supernatants to degrade AFB₁ was 8.0 in Na₂HPO₄/NaH₂PO₄ buffer and that the optimum temperature was 30℃. Under the optimized condition, the degradation rate of 50 and 100 ng/mL AFB₁ in 96 h of strain supernatant was 90.50% and 75.68%, respectively. Moreover, the genotoxicity test results of the degradation products showed that the degradation products did not show genotoxicity. In addition, GDAAS003 could inhibit AFB₁ synthesis by A. flavus in maize.【Conclusion】Streptomyces GDAAS003 not only degraded AFB₁ with high efficiency, but also inhibited the growth of A. flavus. It has a great application prospect in the food and feed industries.