The present invention relates to a system for improving a strain of filamentous fungus that is useful in producing an enzyme of interest such as a cellulase. The invention involves generating genetic diversity in a strain of fungal cells, subjecting the population of cells to selection, and isolating the cells that overproduce the enzyme. The selection techniques involve culturing the population of cells in purified cellulose and/or at an elevated temperature that is adverse to production of the enzyme.
1. GOVERNMENT SUPPORT
 Portions of this work were funded by Subcontract No. ZCO-30017-01 with the National Renewable Energy Laboratory under Prime Contract No. DE-AC36-99GO10337 with the U.S. Department of Energy. Accordingly, the United States Government may have certain rights in this invention.