β-xylanase from Thermomyces lanuginosus and its biobleaching application

Abstract

Thermomyces lanuginosus is thermophilic fungus in which was isolated from widespread material. A high number of this fungus was found in composts especially mushroom composts. This fungus has been reported to produce a high level xylanase when cultivated in the medium containing xylan and corn cob as a carbon source. Various strains of T. lanuginosus produced a single xylanase with molecular masses in range of 22.0 to 29.0 kDa. Pure β-xylanase obtained from various strains of this fungus exhibited highly stability at high temperature and wide pH range. The optimal temperature and optimal pH of pure β-xylanase from various strains of T. lanuginosus have been reported in range of 60-75°C and pH 6.0-7.0, respectively. The great thermal stability was resulting from the present of hydrophilic amino acid on beta sheet of the surface of xylanase structure. Moreover, the relatedness between high and low xylanase producing strains can be distinguish by random amplification of polymorphic DNA (RAPD). Based on nucleotide sequences and T. lanuginosus xylanase gene has been classified to be a member of family 11 (formerly known as cellulase family G) glycosyl hydrolases. This enzyme was endo-type xylanase having main product are xylose and xylobiose. The expression of xylanase gene from T. lanuginosus was achieved in Escherichia coli and methylotrophic yeast Pichia pastoris. The ability of T. lanuginosus in which produced large amount of high thermos stable xylanase has made this fungus to be a source of xylanase production for biobleaching in pulp and paper process. © 2010 Asian Network for Scientific Information.