Chong Barrie Fong, Harrison Mark D, O'Hara Ian M
Syngenta Centre for Sugarcane Biofuels Development, Queensland University of Technology, GPO Box 2432, 2 George Street, Brisbane, Queensland 4001, Australia.
Syngenta Centre for Sugarcane Biofuels Development, Queensland University of Technology, GPO Box 2432, 2 George Street, Brisbane, Queensland 4001, Australia.
Enzyme Microb Technol. 2014 Jul-Aug;61-62:55-60. doi: 10.1016/j.enzmictec.2014.04.015. Epub 2014 May 2.
Recent developments in chemical pretreatments of lignocellulosic biomass using polyols as co-solvents (e.g., glycerol and ethylene glycol) at temperatures less than 100°C may allow the effective use of thermostable and non-thermostable cellulases in situ during the saccharification process. The potential of biomass saccharifying enzymes, endoglucanases (EG) from a thermophilic bacterium (Thermotoga maritima) and a mesophilic fungus (Trichoderma longibrachiatum), to retain their activity in aqueous buffer, acidified glycerol, and acidified ethylene glycol used as co-solvents at pretreatment temperatures at or below 100°C were examined. The results show that despite its origin, T. longibrachiatum EG (Tl-EG) retained 75% of its activity after exposure to 100°C for 5 min in aqueous buffer while T. maritima EG (Tm-EG) retained only 5% activity. However, at 90°C both enzymes retained over 87% of their activity. In acidified (0.1% (w/w) H2SO4) glycerol, Tl-EG retained similar activity (80%) to that obtained in glycerol alone, while Tm-EG retained only 35%. With acidified ethylene glycol under these conditions, both Tl-EG and Tm-EG retained 36% of their activity. The results therefore show that Tl-EG is more stable in both acidified glycerol and ethylene glycol than Tm-EG. A preliminary kinetic study showed that pure glycerol improved the thermal stability of Tl-EG but destabilized Tm-EG, relative to the buffer solution. The half-lives of both Tl-EG and Tm-EG are 4.5 min in acidified glycerol, indicating that the effectiveness of these enzymes under typical pretreatment times of greater than 15 min will be considerably diminished. Attempts have been made to explain the differences in the results obtained between the two enzymes.
近期，在低于100°C的温度下使用多元醇（如甘油和乙二醇）作为共溶剂对木质纤维素生物质进行化学预处理的进展，可能使糖化过程中能够原位有效利用耐热和不耐热的纤维素酶。研究了来自嗜热细菌（海栖热袍菌）和嗜温真菌（长枝木霉）的生物质糖化酶——内切葡聚糖酶（EG），在用作共溶剂的水性缓冲液、酸化甘油和酸化乙二醇中，于100°C及以下的预处理温度下保持其活性的潜力。结果表明，尽管来源不同，但长枝木霉EG（Tl-EG）在水性缓冲液中于100°C暴露5分钟后仍保留其75%的活性，而海栖热袍菌EG（Tm-EG）仅保留5%的活性。然而，在90°C时，两种酶均保留了超过87%的活性。在酸化（0.1%（w/w）H2SO4）甘油中，Tl-EG保留的活性（80%）与仅在甘油中获得的活性相似，而Tm-EG仅保留35%。在这些条件下的酸化乙二醇中，Tl-EG和Tm-EG均保留了36%的活性。因此，结果表明Tl-EG在酸化甘油和乙二醇中均比Tm-EG更稳定。一项初步动力学研究表明，相对于缓冲溶液，纯甘油提高了Tl-EG的热稳定性，但使Tm-EG不稳定。在酸化甘油中，Tl-EG和Tm-EG的半衰期均为4.5分钟，这表明在大于15分钟的典型预处理时间下，这些酶的有效性将大大降低。已尝试解释两种酶所得结果的差异。
