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

地球上的主要生物量包括树木和农作物。农业残渣是农作物收获后残留的一种主要生物质物质，可用于生产乙醇等可再生能源。残渣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，以及难以由微生物高效地生产乙醇。人们非常希望对原材料进行最小限度的预处理，并实现最大限度地将生物转化为可再生能源。嗜热菌是一类可以在121℃以下生长的微生物，它们具有高度耐热的酶，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，在农业和树木残渣的生物转化方面具有巨大的潜力。预计在较高的温度下，纤维素和半纤维素材料的转化率会更高。我们这项研究的长期目标是开发一种使用耐热和熟练的酶来转化纤维素和半纤维素材料的高效酶系统。我们这项建议的具体目标是：鉴定和鉴定新的水解酶和戊糖代谢途径中的关键酶；提高酶活性，用于农业残渣的转化。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的发现，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原料转化的耐热酶提供核心信息。

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.