摘要:
采用淀粉平板和羧甲基纤维素钠(CMC-Na)平板从选取的140株芽胞杆菌中初筛出8株具有产纤维素酶和淀粉酶复合酶芽胞杆菌,经酶活力测定解淀粉芽胞杆菌FJAT-8754(Bacillus amyloliquefaciens)具有较高的淀粉酶、纤维素酶活力。通过研究解淀粉芽胞杆菌FJAT-8754的生长、产酶曲线以及酶学特性,确定在发酵28h后菌体生长进入稳定期,培养44h时发酵液中活菌数达到最大为4.41×109 cfu·mL-1,在36h时纤维素酶、淀粉酶均达到酶活最高峰,酶活分别为135.8、1 543.3U·mL-1;纤维素酶反应最适pH值为5.5、最适温度为50℃,Vmax为5.14×10-3 mg·mL-1·min-1、Km值为7.71×10-1 mg·mL-1;淀粉酶反应最适pH值为5.5、最适温度为55℃,Vmax为3.35×10-2 mg·mL-1·min-1、Km值为6.03×10-3 mg·mL-1。采用3因素7水平,即U7(73)均匀设计法优化解淀粉芽胞杆菌产酶条件,确定产纤维素酶、淀粉酶的最优条件均为:初始pH值6.2、培养温度37.5℃、转速180r·min-1,优化后解淀粉芽胞杆菌FJAT-8754纤维素酶活力为202.9U·mL-1、淀粉酶活力为2 392.9U·mL-1。
Abstract:
Eight Bacillus strains which produce cellulase and amylase were screened from 140standard Bacillus strains by using starch medium and carboxymethylcellulose sodium(CMC-Na)plate screening method.FJAT-8754had the highest cellulase and amylase producing activities and the biological characterizes(e.g.growth curves,dynamic changes of enzyme activity and enzymatic properties)were tested.Our results suggested that the stationary phase of FJAT-8754was at 28h,the colony count was 4.41×109 cfu·mL-1 at 44hand the activity of cellulase and amylase peaked at 36hsimultaneously.Meanwhile,the optimum reaction conditions for cellulase were at pH5.5,55℃,Vmaxwas 5.14×10-3 mg·mL-1·min-1 and Km was 7.71×10-1 mg·mL-1;the optimal reaction conditions of amylase were at pH 5.5,60℃,Vmaxwas 3.35×10-2 mg·mL-1·min-1 and Km was 6.03×10-3 mg·mL-1.Furthermore,uniform design assays showed that the optimal submerged culture conditions for cellulase and amylase was at pH 6.2,fermentation temperature was at 37.5℃,shaking speed was 180r·min-1,and the activity of cellulase and amylase could reach 202.9,2 392.9U·mL-1,respectively.
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