Enzymatic conversion of hemi/cellulosic residues using novel thermostable enzymes from hyperthermophiles

地球上的主要生物物质包括树木和农作物。农业残留物是农作物收获后残留的一种主要生物质材料，可用于生产乙醇等可再生能源。残基生物转化的主要障碍是难以利用其几乎不溶的成分，纤维素和半纤维素，以及微生物高效生产乙醇。使用最少的预处理原料并实现最大限度的生物转化为可再生能源是非常理想的。超嗜热微生物是一组可以在121°C的温度下生长的微生物，它们具有高度热稳定性的酶，如纤维素酶和木聚糖酶，以及其他催化进一步代谢过程以产生乙醇的酶，这在农业和树木残留物的生物转化应用中具有很大的潜力。预计在高温下，纤维素和半纤维素材料的转化率将会更高。我们这项研究的长期目标是开发一种高效的酶系统，用于使用耐热和高效的酶转化纤维素和半纤维素材料。我们的具体目标是：鉴定和表征戊糖代谢途径中涉及的新型水解酶和关键酶；提高酶的活性，用于农业残留物的转化。新型纤维素酶和半纤维素酶的发现，以及与戊糖利用有关的新型酶，将有助于改进目前使用的工业发酵工艺，并为生产催化木质纤维素材料转化的热稳定酶提供核心信息。

Major biomass on earth comprises trees and crops. Agricultural residues are a major type of biomass material remaining after harvesting agricultural crops and can be used for producing renewable energy sources such as ethanol. The main obstacle for bioconversion of the residues is difficulty in utilization of their virtually insoluble components, cellulose and hemicellulose, and in high efficient production of ethanol by microorganisms. It is highly desirable to use minimal pretreatment of the raw materials and achieve maximal bioconversion to renewable energy sources. Hyperthermophiles are a group of microorganisms that can grow at temperatures up to 121°C, and they possess highly thermostable enzymes, such as cellulase and xylanase, and other enzymes catalyzing further metabolic processes towards the production of ethanol, which have great potential in the application of bioconversion of agricultural as well as tree residues. It is also expected thatconversion rate of the cellulosic and hemicellulosic materials will be higher at elevated temperatures. Our long-term goal of this research is to develop a highly efficient enzymatic system for the conversion of cellulosic and hemicellulosic materials using thermostable and proficient enzymes. Our specific objectives of this proposal are: to identify and characterize novel hydrolases and key enzymes involved in pentose metabolic pathway; to enhance enzymatic activities for being used for the conversion of agricultural residues. The discovery of new types of cellulase and hemicellulase, and novel enzymes involved in pentose utilization, will help improve currently used industrial fermentation processes and provide central information for production of thermostable enzymes catalyzing the conversion of lignocellulosic materials.