关键词: 木质纤维素, 嗜热厌氧菌, 糖苷水解酶, 生物燃料

Abstract: As a gram-positive anaerobic bacterium isolated from hot spring，Caldicellulosiruptor bescii has strong ability in degrading lignocellulose. It can rapidly grow on a variety of model plant cell wall polysaccharide compounds such as the crystalline cellulose avicel，xylan or even on unpretreated lignocellulose such as switchgrass as sole carbon source. Moreover，this bacterium has an unusual ability of anaerobic degradation of lignin. The genomic annotation showed that most of the proteins encoded by this bacterium were multivariate bi-functional enzymes，i.e.，the N-terminal and C-terminus of the polypeptide chain were glycoside hydrolases of different families，with 2-3 carbohydrate binding domains. The genes encoding enzymes of degrading cellulose were concentrated in a plant cell wall polysaccharide degradation gene cluster，such as cellulase/xylanase，cellulase/mannanase，cellulase/xyloglucanase，etc. The xylanase of C. bescii belonged to the GH10 family，whose specificity of the enzyme was broad，and the homology of the amino acid sequence was between 18.7% and 59.5%. The genus Caldicellulosiruptor evolved a series of mechanisms that allowed glycoside hydrolyses to absorb better to substrates，bacteria and lignocellulose，thereby facilitating the enzymatic hydrolysis of lignocellulose. There were 12 proteins containing SLH domain，and the newly discovered adhesion protein Tāpirin in C. bescii may be involved in the absorption and utilization of lignocellulose. In this paper we review the current progresses in exploring the genome of C. bescii for novel glycoside hydrolases targeting plant cell wall and the associated molecular mechanisms，which are of great significance for the design and optimization of efficient and multi-function lignocellulose degradation enzymes.

Key words: lignocellulose, Caldicellulosiruptor bescii, glycoside hydrolase, biofuels