P11: Characterization of a novel multi-functional cellulase CHU_2103 from Cytophaga hutchinsonii

Cytophaga hutchinsonii is a Gram-negative gliding bacterium which can degrade crystalline cellulose efficiently with an unknown strategy. The bioinformatic analysis indicated it had no processive cellulase which is esssential for crystalline cellulose digestion. Here, one of the predicted endo-glucanases, CHU_2103, was expressed successfully in E. coli JM109 and proved to be a multi-functional cellulase including processive endo-glucanase, cellobihydrolase and transglycosylation activities within one catalytic domain. Besides this, CHU_2103 could bind to crystalline cellulase without any known cellulose binding domain. It could hydrolyze carboxymethyl cellulose (CMC) into oligo-saccharides and decreased the viscosity of CMC in a short time. When regenerated amorphous cellulose (RAC) was degraded by CHU_2103, the main soluble products were cellobiose and cellotriose. The ratio of the generated soluble reducing ends to insoluble reducing ends reached as high as 4, which indicated it was a processive endo-glucanase. Also it could degrade p-Nitrophenyl β-D-cellobioside like a cellobihydrolase. When hydrolyzing p-Nitrophenyl β-D-cellotrioside, besides glucose, cellobiose and cellotriose, larger oligo-saccharides including cellotetrose and cellopentose could also be detected indicating it had transglycosylation activity. The hydrolysis pattern of CHU_2103 was studied with different oligo-caccharides as the substrate. Ca²⁺ and Zn²⁺ could increase its CMCase activity while Mg²⁺ decreased the activity. The multi-functional cellulase maybe an important part of the efficient cellulolytic system of Cytophaga hutchinsonii.