MUTANT XYLANASE MANUFACTURING METHOD AND USE THEREFOR AND METHOD FOR MANUFACTURING SACCHARIFIED LIGNOCELLULOSE

The present invention relates to an inexpensive and efficient saccharification method for lignocellulose using a thermostable xylanase and provision of a mutant xylanase that has a substitute amino acid residue， and that exhibits stable activity even under severe conditions in which enzymes easily inactivate， and that provides an initial rate of reaction not significantly reduced as compared to a wild-type xylanase corresponding to the mutant xylanase. Provided is a method of producing a saccharified product of lignocellulose， including contacting a lignocellulosic raw material with a thermostable xylanase， and a mutant xylanase that provides an initial rate of reaction that is at least 70% of that provided by a wild-type xylanase corresponding thereto， that has a xylanase activity after heat treatment at 50°C for 24 hours that is at least 50% of its xylanase activity before the heat treatment， and that has a substitute amino acid residue. The present invention addresses the following problems: providing an inexpensive， efficient lignocellulose saccharification method using a thermostable xylanase; and providing a mutant xylanase that has a substituted amino-acid residue， exhibits stable activity even under harsh conditions in which enzymes are easily deactivated， and has an initial reaction rate not much less than that of the corresponding wild-type xylanase. A lignocellulose saccharification method that includes bringing a lignocellulose feedstock into contact with a thermostable xylanase; and a mutant xylanase that has a substituted amino-acid residue， has an initial reaction rate at least 70% of that of the corresponding wild-type xylanase， and， after a 24-hour heat treatment at 50°C， exhibits xylanase activity at least 50% of that exhibited before said heat treatment.