Improvement of fungal arabinofuranosidase thermal stability by reversible immobilization

► An α-l-arabinofuranosidase GH51 was successfully secreted by Aspergillus nidulans. ► AbfA hydrolyzed arabinoxylan, xylan, debranched arabinan and pnp-arabinofuranoside. ► AbfA was highly stabilized by reversible immobilization onto Sepharose-Q. ► Immobilized AbfA showed a synergistic effect on arabinoxylan hydrolysis. A gene encoding α-l-arabinofuranosidase (abfA) from Aspergillus niveus was identified, cloned, and successfully expressed in Aspergillus nidulans. Based on amino acid sequence comparison, the 88.6kDa enzyme could be assigned to the GH family 51. The characterization of the purified recombinant AbfA revealed that the enzyme was active at a limited pH range (pH 4.0–5.0) and an optimum temperature of 70°C. The AbfA was able to hydrolyze arabinoxylan, xylan from birchwood, debranched arabinan, and 4-nitrophenyl arabinofuranoside. Synergistic reactions using both AbfA and endoxylanase were also assessed. The highest degree of synergy was obtained after the sequential treatment of the substrate with endoxylanase, followed by AbfA, which was observed to release noticeably more reducing sugars than that of either enzyme acting individually. The immobilization of AbfA was performed via ionic adsorption onto various supports: agarose activated by polyethyleneimine polymers, cyanogen bromide activated Sepharose, DEAE-Sepharose, and Sepharose-Q. The Sepharose-Q derivative remained fully active at pH 5 after 360min at 60°C, whereas the free AbfA was inactivated after 60min. A synergistic effect of arabinoxylan hydrolysis by AbfA immobilized in Sepharose-Q and endoxylanase immobilized in glyoxyl agarose was also observed. The stabilization of arabinofuranosidases using immobilization tools is a novel and interesting topic.