Regulation of cellulase biosynthesis and secretion in fungi.

The cellulase complex of the mesophilic fungus Trichoderma reesei is capable of efficiently hydrolysing crystalline cellulose to glucose and provides a potential route to the conversion and recycling of renewable cellulosic biomass. To date, however, the high cost of these enzymes has hampered their large-scale industrial application. This high cost is principally due to the low yield and low specific activity of enzymes produced by the available microbial strains. In recent years a number of improved mutant strains have been isolated, many of which produce as much as 20mg of extracellular protein/ml with substantial increases in yields of cellulase (for a review see Montenecourt, 1983). However, only one strain, RL-P37, exhibits an increase in specific activity (Sheir-Neiss & Montenecourt, 1984). In spite of the improvements that have been made in strain development of T. reesei, major new advances cannot be anticipated until the mechanisms controlling the synthesis and secretion of cellulases are fully understood.