Reformulating the Hydrolytic Enzyme Cocktail of by Combining XYR1 Overexpression and Elimination of Four Major Cellulases to Improve Saccharification of Corn Fiber.

The industrial fungus has an outstanding capability of secreting an enzyme cocktail comprising multiple plant biomass-degrading enzymes. Herein, the overexpression of XYR1, the master transactivator controlling (hemi)cellulase gene expression, was performed in lacking four main cellulase-encoding genes. The resultant strain Δ4OE1 was able to produce a dramatically different profile of secretory proteins on soluble glucose or lactose compared with that of the wild-type . The Δ4OE1 secretome included cellulases EGIII and BGLI as well as several hemicellulases and nonhydrolytic cellulose degradation-associated proteins that are not preferentially induced in the wild-type strain. Δ4OE1 produced a significant amount of α-arabinofuranosidase I on lactose, and the crude enzyme cocktail of Δ4OE1 not only released a considerable quantity of glucose but also exhibited remarkable performance in the hydrolytic release of xylose, arabinose, and mannose from un-pretreated corn fiber. These results showed that the engineered strain holds great potential for improving the saccharification efficiency of the hemicellulosic constituents within corn fiber.