초록
Two recombinant arabinosyl hydrolases, α-<sub>L</sub>-arabinofuranosidase from Geobacillus sp. KCTC 3012 (GAFase) and endo-(1,5)-α-<sub>L</sub>-arabinanase from Bacillus licheniformis DSM13 (BlABNase), were overexpressed in Escherichia coli, and their synergistic modes of action against sugar beet (branched) arabinan were investigated. Whereas GAFase hydrolyzed 35.9% of <sub>L</sub>-arabinose residues from sugar beet (branched) arabinan, endo-action of BlABNase released only 0.5% of <sub>L</sub>-arabinose owing to its extremely low accessibility towards branched arabinan. Interestingly, the simultaneous treatment of GAFase and BlABNase could liberate approximately 91.2% of <sub>L</sub>-arabinose from arabinan, which was significantly higher than any single exo-enzyme treatment (35.9%) or even stepwise exo- after endo-enzyme treatment (75.5%). Based on their unique modes of action, both exo- and endo-arabinosyl hydrolases can work in concert to catalyze the hydrolysis of arabinan to <sub>L</sub>-arabinose. At the early stage in arabinan degradation, exo-acting GAFase could remove the terminal arabinose branches to generate debranched arabinan, which could be successively hydrolyzed into arabinooligosaccharides via the endo-action of BlABNase. At the final stage, the simultaneous actions of exo- and endo-hydrolases could synergistically accelerate the <sub>L</sub>-arabinose production with high conversion yield.