Cloning and characterization of two cellulase genes from Lentinula edodes

Lentinula edodes has traditionally been grown on fallen logs. It produces a wide array of enzymes to digest the lignocellulolytic substrate for nutrients. Thus, this organism represents a rich source of potentially potent lignocellulolytic enzymes that can be harnessed for conversion of biomass to simple sugars. These sugars can then be used as feedstock for ethanol production or other chemical syntheses. We have cloned two cellulase genes from L. edodes grown on a wood substrate without the use of genomic or cDNA libraries by using a PCR-based strategy employing degenerate primers directed at the cellulose-binding domain. cel7A encoded a 516-amino acid protein that belonged to glycosyl hydrolase family 7 and had sequence similarities to cbhI genes from other fungi. cel6B encoded a 444-amino acid protein that belonged to glycosyl hydrolase family 6 and had sequence similarities to cbhII genes from other fungi. We demonstrated that cel7A and cel6B transcript levels were positively correlated to L. edodes growth in the presence of crystalline cellulose.