PMAS, Arid Agriculture University, Islamabad, Punjab, Pakistan.
Appl Biochem Biotechnol. 2013 Jun;170(4):895-908. doi: 10.1007/s12010-013-0227-x. Epub 2013 Apr 25.
Fungi are considered good producers of industrially valuable enzymes with higher enzymatic activities. Among these cellulases are group of extracellular enzymes commonly employed in many industries for the hydrolysis of cellulolytic material. Aspergillus fumigatus produced exoglucanase having high enzymatic activity (83 U/gds) during the solid-state fermentation of wheat straw under optimum physical and nutritional conditions. Maximum production was obtained after 72 h of fermentation, at 55 °C temperature, pH 5.5, 80 % moisture level, and 2 mL fungal inoculum. Production was further increased by the addition of fructose (0.3 %) as additional carbon source, peptone (0.4 %) as nitrogen source, Tween-80 (0.3 %) as surfactant, and ammonium sulfate (0.2 %) in media. Exoglucanase was 2.30-folds purified by adding 40 % ammonium sulfate with volumetric activity 95.4 U/gds and specific activity 14.74 U/mg. Further, it was 5.18-folds purified by gel filtration chromatography with volumetric activity 115.2 U/gds and specific activity 33.10 U/mg. Purified exoglucanase has maximum activity at 55 °C and pH 4.8 using 1 % Avicel aqueous solution as substrate. The K(m) and V(max) were 4.34 mM and 7.29 μM/min, respectively. Calcium, magnesium, and zinc ions have positive effect on exoglucanase activity.
真菌被认为是具有较高酶活的工业价值酶的良好生产者。在这些纤维素酶中，外切葡聚糖酶是一组常用于许多工业领域的纤维素水解酶。在优化的物理和营养条件下，烟曲霉在麦秸固态发酵过程中产生具有高酶活（83 U/gds）的外切葡聚糖酶。在发酵 72 小时后，在 55°C 温度、pH5.5、80%水分水平和 2 毫升真菌接种量下，获得最大产量。通过在培养基中添加果糖（0.3%）作为额外的碳源、蛋白胨（0.4%）作为氮源、吐温-80（0.3%）作为表面活性剂和硫酸铵（0.2%），可以进一步提高产量。通过添加 40%的硫酸铵，外切葡聚糖酶的比活提高了 2.30 倍，达到 95.4 U/gds，比活为 14.74 U/mg。进一步通过凝胶过滤色谱法纯化，比活提高了 5.18 倍，达到 115.2 U/gds，比活为 33.10 U/mg。纯化的外切葡聚糖酶在 55°C 和 pH4.8 下，使用 1%的 Avicel 水溶液作为底物时具有最大活性。K(m)和 V(max)分别为 4.34 mM 和 7.29 μM/min。钙离子、镁离子和锌离子对外切葡聚糖酶的活性有积极影响。
