α-淀粉酶在郫县豆瓣发酵过程中具有重要的作用,不仅能为郫县豆瓣中的微生物提供碳源,还能在微生物作用及化学反应下生成各类风味物质。豆瓣酱中黄曲霉毒素的污染是行业关注的问题,排除菌株产黄曲霉毒素的可能性,是筛选高效菌株的必要条件。从传统的豆瓣曲中筛选得到4株产α-淀粉酶活力较高的菌株,其中米曲霉30M-1发酵曲精的α-淀粉酶活力高达3 497 U/g,菌株16、FN、DM2发酵曲精的酶活力也可达到2 000 U/g。采用ITS(internal transcribed spacer identification)测序构建系统发育树,结合形态观察,研究菌株产黄曲霉毒素B1(aflatoxin B1, AFB1)基因的表达及产AFB1的可能性。测定的结果显示,4株菌株与米曲霉同源性更近,没有造成AFB1污染的风险,说明所筛选的高产淀粉酶的霉菌具有提高豆瓣酱产品发酵效率的可能性。
α-Amylase plays an important role in the fermentation of Pixian broad bean chili paste and the pollution of aflatoxin B1 (AFB1) in Pixian broad bean chili paste is the main public concern. To eliminate aflatoxin formation it is necessary to screen and select the high-efficiency α-amylase-producing strains with no aflatoxin synthesis. Four isolates with high-yield of α-amylase were screened from the traditional broad bean koji samples. The α-amylase activity of broad bean fermentation products by strain 30M-1 was up to 3497 U/g, the enzyme activities of strain 16, FN and DM2 were also higher than 2000 U/g. Using the ITS sequencing, phylogenetic analysis, morphologic observation, PCR amplification of AFB1 genes and detection of AFB1 in the strain fermentation broth, all four isolates were more closely to Aspergillus oryzae with no risk of AFB1 contamination. In conclusion, the four Aspergillus oryzae isolates with high-yield of α-amylase in this research have the potential to be used in Pixian broad bean chili paste fermentation for improving fermentation efficiency.
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