Production and properties of hemicellulases by a Thermomyces lanuginosus strain
Thermophilic fungi producing extremely high β-xylanase and their associated hemicellulases have attracted considerable attention because of potential industrial applications. Thermomyces lanuginosus strain SSBP isolated from soil, produced β-xylanase activity of 59 600 nkat ml-1 when cultivated on a medium containing corn cobs as substrate and yeast extract as nitrogen source. Lower β-xylanase activities were produced after growth on other xylan substrates, sugars and soluble starch. Other hemicellulases were produced extracellularly at significantly lower levels than the β-xylanase activity produced on corn cobs. No cellulase activity was observed. The optimal conditions for β-xylanase production were 50 °C and pH 6.5, whereas 70 °C and between pH 5.5 and 9.5 were optimal for β-xylanase activity. The temperature optima for other hemicellulases were less than the xylanase with the exception of β-mannosidase. The pH optima of the other hemicellulases were between 5.0 and 6.5. Xylanase was stable up to 70 °C and between pH 5.5 and 9.0 for 30 min whereas the other hemicellulase were less stable. These results suggest that the most suitable conditions for hydrolysis of hemicellulose by these enzymes would be at 50 °C and pH 6.0.