A novel bifunctional GH51 exo-α-l-arabinofuranosidase/endo-xylanase from Alicyclobacillus sp. A4 with significant biomass-degrading capacity

Abstract

BackgroundImproving the hydrolytic performance of xylanolytic enzymes on arabinoxylan is of importance in the ethanol fermentation industry. Supplementation of debranching (arabinofuranosidase) and depolymerizing (xylanase) enzymes is a way to address the problem. In the present study, we identified a bifunctional α-l-arabinofuranosidase/endo-xylanase (Ac-Abf51A) of glycoside hydrolase family 51 in Alicyclobacillus sp. strain A4. Its biochemical stability and great hydrolysis efficiency against complex biomass make it a potential candidate for the production of biofuels.ResultsThe gene encoding Ac-Abf51A was cloned. The comparison of its sequence with reference proteins having resolved 3D-structures revealed nine key residues involved in catalysis and substrate-binding interaction. Recombinant Ac-Abf51A produced in Escherichia coli showed optimal activity at pH 6.0 and 60 °C with 4-nitrophenyl-α-l-arabinofuranoside as the substrate. The enzyme exhibited an exo-type mode of action on polyarabinosides by catalyzing the cleavage of α-1,2- and α-1,3-linked arabinofuranose side chains in sugar beet arabinan and water-soluble wheat arabinoxylan and α-1,5-linked arabinofuranosidic bonds in debranched sugar beet arabinan. Surprisingly, it had capacity to release xylobiose and xylotriose from wheat arabinoxylan and was active on xylooligosaccharides (xylohexaose 1.2/mM/min, xylopentaose 6.9/mM/min, and xylotetraose 19.7/mM/min), however a lower level of activity. Moreover, Ac-Abf51A showed greater synergistic effect in combination with xylanase (2.92-fold) on wheat arabinoxylan degradation than other reported enzymes, for the amounts of arabinose, xylose, and xylobiose were all increased in comparison to that by the enzymes acting individually.ConclusionsThis study for the first time reports a GH51 enzyme with both exo-α-l-arabinofuranosidase and endo-xylanase activities. It was stable over a broad pH range and at high temperature, and showed greater synergistic effect with xylanase on the degradation of wheat arabinoxylan than other counterparts. The distinguished synergy might be ascribed to its bifunctional α-l-arabinofuranosidase/xylanase activity, which may represent a possible way to degrade biomass at lower enzyme loadings.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0366-0) contains supplementary material, which is available to authorized users.

Synergistic degradation of arabinoxylan by free and immobilized xylanases and arabinofuranosidase

“…For example, Yang and coworkers recently reported a bifunctional AFase from glycoside hydrolase (GH) family 51 that has the activity of both arabinofuranosidase and β-xylosidase. It worked synergistically with endoxylanase XynBE18 in the degradation of wheat arabinoxylan, increasing the production of sugar about 3-fold [5].…”

Comparative genomic and secretomic characterisation of endophytic Bacillus velezensis LC1 producing bioethanol from bamboo lignocellulose

“…xylobiose and xylooligomers. Acetyl xylan esterase is an accessory enzyme that functions synergistically with other enzymes in removing side chain residues from the hemicellulose backbone [50,51]. In the present study, four hemicellulases were identified, consisting of one arabinogalactan endo-β-1,4-galactanase (GH53) (1384349889), one beta-xylanase (GH43) (1384351325), one glucuronoxylanase (GH30) (1384349284), and one acetylxylan esterase (CE1) (1384350660) ( Table 3).…”

A Glycoside Hydrolase Family 62 A-L-Arabinofuranosidase from Trichoderma Reesei and Its Applicable Potential during Mashing

“…A GH51 AFase from Alicyclobacillus sp. has also been reported to exhibit exoxylanase activity on soluble wheat arabinoxylan and sugar beet arabinan [45]. Wood and Macrae [46] reported that a GH62 AFase from Aspergillus awamori also showed the capacity to split off β-D-xylopyranosyl units from the main chain of arabinoxylan.…”