不同菌种制备酱油大曲生产酶系特性及其耐盐性的比较

采用4株米曲霉菌种(j2、y2、x42、x72)与对照米曲霉菌株(沪酿3.042)制备大曲,探究其所产中性蛋白酶、酸性蛋白酶、α-淀粉酶以及糖化酶在盐浓度为0%、5%、10%、15%、20%下酶活力变化。实验结果表明,5株菌株所产酶系中,中性蛋白酶活随盐水浓度的增加显著(P<0.05)下降,酸性蛋白酶和糖化酶在5%盐浓度下活力显著下降(P<0.05),随后酶活力下降速率减慢,α-淀粉酶在5%的盐浓度下无显著下降(P>0.05),随后下降速率加快。此外,相同盐浓度下淀粉酶比蛋白酶更稳定,5株米曲霉菌株的α-淀粉酶和糖化酶在20%的盐浓度下残留率均达到50%。菌株y2、j2所产中性蛋白酶和菌株x72所产酸性蛋白酶的耐盐性优于对照菌株。

Effects of Sodium Chloride Concentration on the Activities of Proteases and Amylases in Koji molds

The activity of protease and amylase from four strains(j2,y2,42,x72) were compared with Aspergillus oryzae 3.042,and the changes with various salinity of 0%,5%,10%,15%,20% were measured.The activity of neutral protease decreased significantly(P<0.05) with the increase of salt concentration.The activity of acidic protease and glucoamylase were decreased drastically(P<0.05) under 5% salt concentration and followed by a gently decline.The activity of α-amylase at 5% salt concentration had no significant decrease(P>0.05) but followed by a steep drop.Besides,the amylase was much more stable than the protease in the same sodium chloride solution,and the residual activities of α-amylase and glucoamylase were up to 50% in five strains under 20% salt concentration.The decline rate of neutral protease from strain y2,j2 and acidic protease from strain x72 were all lower than those from control group.