优质米曲霉筛选及复合菌剂构建提升郫县豆瓣蚕豆曲品质

Generation of high-quality Aspergillus oryzae and thus mixed strains to improve the character of broad bean meju of Pixian Douban

郫县豆瓣是我国优势传统发酵食品,其高品质生产具有重要的工业与文化价值。蚕豆曲制备是郫县豆瓣生产的重要工序,目前使用米曲霉沪酿3.042纯菌株作为工业菌剂。米曲霉沪酿3.042水解酶活力较高却酶系不均,获得新的、具有更高且更均匀酶系的优质菌种或复合菌剂用于蚕豆曲生产,将对郫县豆瓣生产品质提升有极大促进作用。该研究自传统酿造食品微生物菌种库中筛选获得并鉴定2株米曲霉菌株,LBM 30007及LBM 30008,经基础发酵表型研究,2株菌在发酵性能方面优势互补:LBM 30007分泌的水解酶活力及分布均匀度高,LBM 30008孢子萌发速率极快。基于此,结合工业米曲霉沪酿3.042的发酵性能,该研究设计了3菌株复合菌剂制曲。经检测,经复合菌剂制作的蚕豆曲中,酸性和中性蛋白酶活力、亮氨酸氨肽酶活力、氨基酸态氮含量及鲜味氨基酸含量较沪酿3.042单菌制曲均有所提升,特别是对郫县豆瓣酿造至关重要的酸性蛋白酶活力提高了23.25%,鲜味氨基酸含量上升11.33%。该研究获得的优质米曲霉菌株/菌剂及复合菌剂构建思路,对包括郫县豆瓣在内的传统高盐高氮发酵食品生产有潜在应用价值。

Pixian Douban(Pixian broad bean paste)is one of the traditional fermented foods,whose high-quality production is of significance for Chinese industrial and cultural development.Broad bean meju production is one of the most important processes for Pixian Douban production.Aspergillus oryzae HN 3.042 is used for the production of broad bean meju.A.oryzae HN 3.042 has high hydrolase activities but unbalanced enzyme system.Obtaining newer and higher-powered koji mold(or mixed strains)for broad bean meju produc-tion will improve the quality of Pixian Douban.Two A.oryzae strains,LBM 30007 and LBM 30008,were selected and identified from tra-ditional fermented food culture collection.After basic fermentation performance analysis,these two strains showed functional complementa-tion:LBM 30007 could secret high activity and balanced hydrolytic enzyme,while LBM 30008 germinated spore with high rate.Thus,three-strain mixed inoculant was designed for broad bean meju production.Using these three-strain koji molds,after 3-days of fermenta-tion,higher activities of acidic protease(improved by 23.25%)and neutral protease were detected,as well as leucine aminopeptidase.And higher concentration of amino acid nitrogen and umami amino acids(improved by 11.33%)were also achieved,compared with that by using A.oryzae HN 3.042.The high quality A.oryzae strains and mixed strains obtained in this study as well as the construction strat-egy for mixed strains will have potential application value for the development of high-salt-nitrogen fermented food.