Deciphering the molecular mechanisms behind cellulase production in Trichoderma reesei, the hyper-cellulolytic filamentous fungus

Abstract

The filamentous fungus Trichoderma reesei is a potent cellulase producer and the best-studied cellulolytic fungus. A lot of investigations not only on glycoside hydrolases produced by T. reesei, but also on the machinery controlling gene expression of these enzyme have made this fungus a model organism for cellulolytic fungi. We have investigated the T. reesei strain including mutants developed in Japan in detail to understand the molecular mechanisms that control the cellulase gene expression, the biochemical and morphological aspects that could favor this phenotype, and have attempted to generate novel strains that may be appropriate for industrial use. Subsequently, we developed recombinant strains by combination of these insights and the heterologous-efficient saccharifing enzymes. Resulting enzyme preparations were highly effective for saccharification of various biomass. In this review, we present some of the salient findings from the recent biochemical, morphological, and molecular analyses of this remarkable cellulase hyper-producing fungus.

Studies of Cellulose and Starch Utilization and the Regulatory Mechanisms of Related Enzymes in Fungi

“…It was originally isolated from the South Pacific [55] and is well known for the ability to secrete large amounts of cellulase, especially when cellulose is used as the carbon source. To date, a large number of studies have deeply explored not only the function of glycoside hydrolase but also the molecular mechanism of regulation of related enzyme-gene expression in T. reesei [56][57][58][59][60]. Due to its industrial importance and the multiple uses of cellulase in T. reesei, many mutants that increase cellulase yield have been acquired through conventional mutagenesis techniques.…”

“…In addition, using a specific screening strategy for candidate regulators of cellulase production, the activator Ace3 was identified [59]. The overexpression of ace3 led to the increase in cellulase gene expression, while its deletion not only resulted in markedly reduced activity of cellulase and hemicellulase but also influenced the expression of the regulator Xyr1 gene [60,124]. The growth of the strain and secretion of a large number of proteins in filamentous fungi is often affected by the ambient pH.…”

New Genomic Approaches to Enhance Biomass Degradation by the Industrial FungusTrichoderma reesei

“…However, considering that the plant biomass is highly recalcitrant, large amounts of enzymes are needed during the hydrolysis process, which make the biofuel production economically unfeasible [ 29 – 31 ]. In this context, Trichoderma reesei may play an important role in decreasing costs for bioethanol production, whereas it is the filamentous fungus with the greatest capacity of degrading the lignocellulosic biomass [ 2 , 15 , 32 ].…”

Molecular Characterization of an Endo-β-1,4-Glucanase, CelAJ93, from the Recently Isolated Marine Bacterium, Cellulophaga sp. J9-3

“…Cellulose is the most abundant biomass on earth and is a renewable energy source that can be continuously biosynthesized using solar energy. Therefore, developing an optimal process for effectively treating and utilizing inexpensive carbon sources, such as cellulose and cellulose-containing waste material, has become of great interest to humankind, as it will help enable a fossil fuel-independent future [2].…”

“…The application of these enzymes to these industrial fields requires the development of stable enzymes that are active at wide pH ranges and at high temperatures [8,9]. Most research on cellulase production has been performed in fungi, such as Trichoderma reesei [2,10]. However, there is currently much research on cellulase production in bacteria because of their faster growth rate compared with fungi [6].…”