Salt-tolerant mechanism of marine Aspergillus niger cellulase cocktail and improvement of its activity

The cellulase cocktail produced by marine Aspergillus niger exhibits a property of salt-tolerance,which is of great potential in cellulose degradation in high salt environment.In order to explain the mechanism on the salttolerance of the cellulase cocktail produced by marine A.niger,six cellulase components(AnCel6,AnCel7A,AnCel7B,AnEGL,AnBGL1 and AnBGL2)were obtained by directed expression.Studies on their enzymatic properties revealed that oneβ-glucosidase(AnBGL2)and one endoglucanase(AnEGL)exhibited an outstanding salttolerant property,and one cellobiohydrolase(AnCel7B)exhibited a certain salt-tolerant property.Subsequent study revealed that the salt-tolerant An EGL and AnCel7B endowed the cellulase cocktail with stronger salttolerant property,while the salt-tolerant An BGL2 had no positive effect.Moreover,after overexpression of AnCel6,AnCel7A,AnCel7B and AnEGL,the activity of cellulase cocktail increased by 80%,70%,63%and 68%,respectively.However,the activity of cellulase cocktail was not improved after overexpression of AnBGL1 and AnBGL2.After mixed-strain fermentation with cellobiohydrolase recombinants(cel6 a,cel7a and cel7b recombinants)and endoglucanase recombinant(egl recombinant),the the activity of cellulase cocktail increased by 114%,102%and91%,respectively.

一株耐盐纤维素酶海洋曲霉的筛选及产酶条件研究

从东海海底泥中分离到了一株耐盐和高产内切葡聚糖酶(CMCase)及β-葡萄糖苷酶(β-Gluase)的海洋曲霉ZJUBE-1,根据形态特征及18SrDNA分析,初步鉴定该菌为黑曲霉(Asper-gillus niger)。通过液体发酵产酶优化,获得最佳培养基组成,质量分数分别为:麸皮2.5%,氯化铵(或蛋白胨、磷酸二氢铵)1%,含NaCl 3.0%～3.6%的人工海水作无机盐液。发酵条件为100mL三角瓶装培养液30mL,在起始pH 6.0、37℃,接种量为6%,180r/min条件下振荡培养7d,测得发酵液中CMCase、β-Gluase酶活及滤纸酶活(FPA)分别为5.3、5.4、0.75U/mL。该菌在NaCl质量分数24%下仍具产酶能力,所产3种纤维素酶的最适反应温度均为65℃,最适反应pH分别为4.0、5.0、5.0;在NaCl质量分数为2%～12%(β-Gluase在2%～16%)范围内,3种酶活力维持较高水平。该菌及其所产纤维素酶的高度耐盐性预示着其在废水处理、纺织业、海洋养殖、海产品加工或海藻的能源化利用等高盐环境下可能有较好的应用前景。

黑曲霉和芽孢杆菌混合菌产纤维素酶的研究

研究了黑曲霉与芽孢杆菌共4株菌的生长及产酶情况,从而确定了4种组合方式,通过比较4组混合菌的酶活大小,最终确定了组合D2-1+S3-7为产纤维素酶酶活最高的混合菌。优化混合菌的最佳发酵条件为:接种量8%(黑曲霉∶芽孢杆菌为1∶1),250mL三角瓶装液量125mL,秸秆和麸皮为碳源(2∶3),蛋白胨和硫酸铵(1∶1)为氮源,碳氮比7∶1,起始pH值为5.0,发酵温度28℃,发酵时间4d,FPA酶活达到535.08U/mL,分别是出发菌黑曲霉D2-1的4.45倍和芽孢杆菌S3-7的4.61倍。