Biotechnological versatility of riboflavin producer Ashbya gossypii Expression of Trichoderma reesei cellulases CBHI and EGI

Abstract

The filamentous fungus Ashbya gossypii shows the potential for the production of, yet unexploited, valuable compounds other than riboflavin. To explore the ability of A. gossypii as a host for the expression of recombinant proteins, endoglucanase I (EGI) and cellobiohydrolase I (CBHI) from the fungus Trichoderma reesei were expressed in A. gossypii under Saccharomyces cerevisiae PGK1 promoter. The proteins were secreted into the culture medium, but there were differences in the amount or activity of the protein being produced. In one hand, CBHI activity was not detected using 4-methylumbelliferyl--Dlactoside as substrate, being only detected by Western blot. On the other hand, EGI activity was detectable, the level of activity being comparable to that produced by a S. cerevisiae strain containing the same plasmid. Thus more EGI was secreted than CBHI, or more active protein was produced. Partial characterization of CBHI and EGI expressed in A. gossypii revealed overglycosylation when compared to the native T. reesei proteins, but the glycosylation was less extensive than on cellulases expressed in S. cerevisiae.