Expression and characterization of a GH43 endo-arabinanase from Thermotoga thermarum

Arabinan is an important plant polysaccharide degraded mainly by two hydrolytic enzymes, endo-arabinanase and α-L-arabinofuranosidase. In this study, the characterization and application in arabinan degradation of an endo-arabinanase from Thermotoga thermarum were investigated. The recombinant endo-arabinanase was expressed in Escherichia coli BL21 (DE3) and purified by heat treatment followed by purification on a nickel affinity column chromatography. The purified endo-arabinanase exhibited optimal activity at pH 6.5 and 75°C and its residual activity retained more than 80% of its initial activity after being incubated at 80°C for 2 h. The results showed that the endo-arabinanase was very effective for arabinan degradation at higher temperature. When linear arabinan was used as the substrate, the apparent K(m) and V(max) values were determined to be 12.3 ± 0.15 mg ml⁻¹ and 1,052.1 ± 12.7 μmol ml⁻¹ min⁻¹, respectively (at pH 6.5, 75°C), and the calculated kcat value was 349.3 ± 4.2 s⁻¹. This work provides a useful endo-arabinanase with high thermostability andcatalytic efficiency, and these characteristics exhibit a great potential for enzymatic conversion of arabinan.