In our previous study, three purified cellulases of Melanocarpus albomyces proved to be effective in biostoning application at neutral pH [Enzyme Microb. Technol., accepted for publication]. We cloned and sequenced three genes of M. albomyces, which encode a 20 kDa and two 50-kDa polypeptides. The 20-kDa protein (Cel45A) and one of the 50-kDa proteins (Cel7A) are endoglucanases of the glycosyl hydrolase families 45 and 7, respectively. The other 50-kDa protein (Cel7B) is a family 7 cellobiohydrolase. None of the cellulases harbors a cellulose binding domain (CBD). These genes were expressed in Trichoderma reesei under the control of the T. reesei cbh1 promoter and the proteins detected in the culture medium. The endoglucanase production levels of the cel45A- and cel7A-transformants were several times higher than those of the parental M. albomyces strain. The sizes of Cel45A, Cel7A and Cel7B proteins produced by the transformants were the same as the sizes of the corresponding proteins purified from M. albomyces. Cellulase preparations produced by the cel45A transformants performed well at neutral pH in stone-washing of denim fabric and caused considerably less backstaining as compared to the acid cellulase product of T. reesei.
- Heterologous expression