Identification and characterization of a new xylanase from Gram-positive bacteria isolated from termite gut (Reticulitermes santonensis)

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• 作者：Christel Matté ; otti^a ; ^{christel.matteotti@ulg.ac.be} ; ^{microbio.gembloux@ulg.ac.be} ; Julien Bauwens^b ; Catherine Brasseur^c ; Cé ; dric Tarayre^d ; Philippe Thonart^d ; Jacqueline Destain^d ; Fré ; dé ; ric Francis^b ; Eric Haubruge^b ; Edwin De Pauw^c ; Daniel Portetelle^a ; Micheline Vandenbol^a
• 关键词：Xylanase ; Enzyme ; Gram-positive bacteria ; Termite ; Acetyl xylan esterase
• 刊名：Protein Expression and Purification
• 出版年：2012
• 出版时间：June, 2012
• 年：2012
• 卷：83
• 期：2
• 页码：117-127
• 全文大小：1592 K

文摘

Termites are world champions at digesting lignocellulosic compounds, thanks to cooperation between their own enzymes and exogenous enzymes from microorganisms. Prokaryotic cells are responsible for a large part of this lignocellulolytic activity. Bacterial enzyme activities have been demonstrated in the higher and the lower termite gut. From five clones of Gram-positive bacteria isolated and identified in a previous work, we constructed a genomic DNA library and performed functional screening for alpha-amylase, beta-glucosidase, and xylanase activities. One candidate, Xyl8B8, showed xylanase activity. Sequence analysis of the genomic insert revealed five complete ORFs on the cloned DNA (5746 bp). Among the encoded proteins were a putative endo-1,4-beta-xylanase (XylB8) belonging to glycoside hydrolase family 11 (GH11). On the basis of sequence analyses, genomic DNA organization, and phylogenetic analysis, the insert was shown to come from an actinobacterium. The mature xylanase (mXylB8) was expressed in Escherichia coli and purified by affinity chromatography and detected by zymogram analysis after renaturing. It showed maximal xylanase activity in sodium acetate buffer, pH 5.0 at 55 ¡ãC. Its activity was increased by reducing agents and decreased by Cu²⁺, some detergents, and chelating agents. Its substrate specificity appeared limited to xylan.