Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Circuito Escolar s/n, Ciudad Universitaria, 04510 Mexico DF, Mexico.
J Ind Microbiol Biotechnol. 2013 Jan;40(1):123-32. doi: 10.1007/s10295-012-1211-0. Epub 2012 Nov 17.
Agave tequilana fructans are the source of fermentable sugars for the production of tequila. Fructans are processed by acid hydrolysis or by cooking in ovens at high temperature. Enzymatic hydrolysis is considered an alternative for the bioconversion of fructans. We previously described the isolation of Aspergillus niger CH-A-2010, an indigenous strain that produces extracellular inulinases. Here we evaluated the potential application of A. niger CH-A-2010 inulinases for the bioconversion of A. tequilana fructans, and its impact on the production of ethanol. Inulinases were analyzed by Western blotting and thin layer chromatography. Optimal pH and temperature conditions for inulinase activity were determined. The efficiency of A. niger CH-A-2010 inulinases was compared with commercial enzymes and with acid hydrolysis. The hydrolysates obtained were subsequently fermented by Saccharomyces cerevisiae to determine the efficiency of ethanol production. Results indicate that A. niger CH-A-2010 predominantly produces an exo-inulinase activity. Optimal inulinase activity occurred at pH 5.0 and 50 °C. Hydrolysis of raw agave juice by CH-A-2010 inulinases yielded 33.5 g/l reducing sugars, compared with 27.3 g/l by Fructozyme(®) (Novozymes Corp, Bagsværd, Denmark) and 29.4 g/l by acid hydrolysis. After fermentation of hydrolysates, we observed that the conversion efficiency of sugars into ethanol was 97.5 % of the theoretical ethanol yield for enzymatically degraded agave juice, compared to 83.8 % for acid-hydrolyzed juice. These observations indicate that fructans from raw Agave tequilana juice can be efficiently hydrolyzed by using A. niger CH-A-2010 inulinases, and that this procedure impacts positively on the production of ethanol.
龙舌兰糖浆中的果聚糖是生产龙舌兰酒的可发酵糖源。果聚糖可通过酸水解或在高温烤箱中烹饪来加工。酶水解被认为是果聚糖生物转化的一种替代方法。我们之前描述了从当地菌株黑曲霉 CH-A-2010 中分离出的胞外菊粉酶。在这里，我们评估了黑曲霉 CH-A-2010 菊粉酶在龙舌兰糖浆果聚糖生物转化中的潜在应用，及其对乙醇生产的影响。通过 Western blot 和薄层色谱分析了菊粉酶。确定了菊粉酶活性的最佳 pH 值和温度条件。比较了黑曲霉 CH-A-2010 菊粉酶与商业酶和酸水解的效率。随后用酿酒酵母发酵所得水解物，以确定乙醇生产的效率。结果表明，黑曲霉 CH-A-2010 主要产生一种外切菊粉酶活性。菊粉酶的最佳活性出现在 pH 值 5.0 和 50°C。用 CH-A-2010 菊粉酶水解生龙舌兰汁可得到 33.5 g/L 的还原糖，而用 Fructozyme（诺维信公司，丹麦 Bagsværd）得到 27.3 g/L，用酸水解得到 29.4 g/L。对水解物进行发酵后，我们观察到用酶降解的龙舌兰汁的糖转化为乙醇的效率为理论乙醇产量的 97.5%，而用酸水解的果汁则为 83.8%。这些观察结果表明，用黑曲霉 CH-A-2010 菊粉酶可以有效地水解生龙舌兰糖浆中的果聚糖，并且该方法对乙醇的生产有积极的影响。
