A role of xylanase, α-L-arabinofuranosidase, and xylosidase in xylan degradation
Renewable natural resources such as xylans are abundant in many agricultural wastes. Penicillium sp. AHT-1 is a strong producer of xylanolytic enzymes. The sequential activities of its xylanase, α-L-arabinofuranosidase, and β-xylosidase on model hemicellulose oatspelt xylan was investigated. Optimum production of the enzymes was found in culture containing oatspelt xylan at 30°C and initial pH 7.0 after 6 days. The enzymes were partially purified by ammonium sulphate fractionation and anion-exchange chromatography on DEAE-Toyopearl 650 S. The apparent molecular mass was 21 kDa, and the protein displayed an "endo" mode of action. The xylanase exhibited glycotransferase activity. It synthesized higher oligosaccharides from the initial substrates, and xylotriose was the shortest unit of substrate transglycosylated. Xylanolytic enzymes (enzyme mixture) produced by this Penicillium sp. interacted cooperatively and sequentially in the hydrolysis of oatspelt xylan in the following order: α-L-arabinofuranosidase [Formula: see text] xylanase [Formula: see text] β-xylosidase. All three enzymes exhibited optimal activity under the same conditions (temperature, pH, cultivation), indicating that they alone are sufficient to completely depolymerize the test xylan. Results indicate that the xylanolytic enzyme mixture of Penicillium sp. AHT-1 could be useful for bioconversion of xylan-rich plant wastes to value-added products.Key words: xylanase, enzyme purification, enzymatic hydrolysis, Penicillium sp. AHT-1.