Characterization of an acetyl xylan esterase Axe7 from Caldicellulosiruptor sp. F32

Abstract:

[Objective] A thermostable acetyl xylan esterase (Axe) was identified from a thermophilic bacterium Caldicellulosiruptor sp. F32. [Methods] Based on genome annotation, protein blast, and protein structural prediction, a family-7 carbohydrate esterase (Axe7) was found. After gene cloning, plasmid construction, protein expression and purification in Escherichia coli, the recombinant protein Axe7 was produced. [Results] On the substrate of 4-Methylumbelliferyl-acetate (4-MUA), the optimal pH of Axe7 was between 6.5 and 7.0, the optimal temperature was 85 °C, and the half-life of Axe7 under the optimal condition was more than 4 hours. By incubation with 1.5 mmol/L different metal ions, the retained activities of Axe7 were between (66.3±4.6)% and (95.7±2.3)%, suggesting the effect of metal ions on enzyme activity. The results of enzyme kinetics showed that the Km of Axe7 was 0.39 mmol/L and kcat was 66.95 s?1. [Conclusion] Our findings provide a potential enzyme for the biorefinery industry.