title: A Novel Multi-domain High Molecular, Salt-Stable Alkaline Xylanase fromAlkalibacteriumsp. SL3.
abstract: A novel multi-domain high molecular xylanase coding gene (xynSL3) was cloned fromAlkalibacteriumsp. SL3, an alkaliphilic bacterial strain isolated from the sediment of soda lake Dabusu. The deduced XynSL3 is composed of a putative signal peptide, three tandem domains of carbohydrate binding module (CBM) family 22, a catalytic domain of glycosyl hydrolase (GH) family 10 and a domain of CBM9. XynSL3 shares the highest identity of 66% to a hypothetical protein fromAlkalibacteriumsp. AK22 and has low identities (33-45%) with other functionally characterized xylanases. The genexynSL3was expressed heterologously inEscherichia coliand the recombinant enzyme demonstrated some particular characteristics. Purified recombinant XynSL3 (rXynSL3) was highly active and stable over the neutral and alkaline pH ranges from 7.0 to 12.0, with maximum activity at pH 9.0 and around 45% activity at pH 12.0. It had an apparent temperature optimum of 55°C and was stable at 50°C. The rXynSL3 was highly halotolerant, retaining more than 60% activity with 3 M NaCl and was stable at up to a 4 M concentration of NaCl. The hydrolysis products of rXynSL3 from corncob xylan were mainly xylobiose and xylotetraose. The activity of rXynSL3 was enhanced by Ca2+and it has strong resistance to sodium dodecyl sulfate (SDS). This multi-domain, alkaline and salt-tolerant enzyme has great potential for basic research and industrial applications such as the biobleaching of paper pulp and production of xylo-oligosaccharides (XOS).
authors.affiliation: Fujian Key Laboratory of Marine Enzyme Engineering, Fuzhou UniversityFuzhou, China; College of Biological Science and Technology, Fuzhou UniversityFuzhou, China.
authors.forename: Guozeng
authors.initials: G
authors.lastname: Wang
authors.affiliation: Fujian Key Laboratory of Marine Enzyme Engineering, Fuzhou UniversityFuzhou, China; College of Biological Science and Technology, Fuzhou UniversityFuzhou, China.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Wu
authors.affiliation: College of Biological Science and Technology, Fuzhou University Fuzhou, China.
authors.forename: Renxiang
authors.initials: R
authors.lastname: Yan
authors.affiliation: Fujian Key Laboratory of Marine Enzyme Engineering, Fuzhou UniversityFuzhou, China; College of Biological Science and Technology, Fuzhou UniversityFuzhou, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Lin
authors.affiliation: Fujian Key Laboratory of Marine Enzyme Engineering, Fuzhou UniversityFuzhou, China; College of Biological Science and Technology, Fuzhou UniversityFuzhou, China.
authors.forename: Xiuyun
authors.initials: X
authors.lastname: Ye
keywords: Alkalibacterium; alkaliphilic; gene cloning; salt-tolerant; soda lake; xylanase