腐乳生产用毛霉高产端肽酶菌株诱变条件及发酵特性的研究

Study on Mutagenesis Conditions of High Exopeptidase-producing Mucor spp.for Sufu Production and Its Fermentation Characteristics

毛霉在腐乳的酿造过程时对腐乳的独特的风味的形成起极其重要的作用,要提高腐乳产品风味,既提高鲜味又降低苦味,从根本上是要解决高蛋白酶系生成及端肽酶产率的问题。本实验通过复合诱变的方法确定一种高产酶系,并端肽酶系含量较高的菌株,通过复合诱变(Co60、紫外)克服单一诱变的缺点,同一诱变因子的重复作用效果不明显,多种诱变因子共同作用效果最好,使菌株产氨基酸的能力提高22%,确定了诱变的辐射剂量在8万伦琴,紫外诱变时间60s为最佳条件。优选出产端肽酶高的菌株,经过诱变,通过新菌种及生产条件的优化,在此基础上又提高30%。确定培养适宜温度为28℃,较佳培养时间48h,最佳起始pH7.2,接菌量10%的培养条件下产蛋白酶活最高,发酵产氨基酸含量也最高,即端肽酶活力最高。由于受腐乳产品自身特点限制,食盐及乙醇的浓度分别设定在6%和4%,为发酵最佳条件。发酵后腐乳产品风味有了明显的改善,鲜味提高、苦味降低。对于生产具有更重要的意义,尤其对提高腐乳这一传统食品的营养效价更具深远意义。

Mucor spp. plays very important role in formation of a unique flavor of sufu in the brewing process. Fundamentally, improving sufu flavor namely the enhancing fresh flavor and reducing of bitterness can be achieved by solving the issues of high production ofproteases and the formation of exopeptidase. This study aimed to obain the mutant strain ofMucor spp. with high production ofproteases and the formation of exopeptidase by compound mutation, which can overcome the disadvantage of single mutation having no obvious repeated effect. Results showed that compared with primitive strain, under the mutagenesis conditions of radiation dose of Co60 8 × 10^4 roentgen and UV mutation time 60 s, the production capacity of amino acid of the mutant strain is increased by 22%. Under the fermentation conditions of culture temperature 28 ℃, time 48 h, initial pH 7.2 and inoculation amount 10%, the production capacity of amino acid of the mutant strain is increased by 30%, and the activity of exopeptidase is the highest. Because of the limitations of sufu product characteristics, the optimal salt and alcohol concentrations for fermentation are set at 6 % and 4 %. After fermentation, the products flavor of sufu is improved significantly, with delicious fresh flavor and little bitterness