Cutting-edge advances in strain and process engineering for boosting cellulase production in Trichoderma reesei

Low-cost production of cellulases is a key factor in advancing the commercialization of lignocellulosic biorefinery. Thus far, Trichoderma reesei is the leading cellulase producer for biorefinery applications. Over 70 years of research, considerable advancements have been made in comprehending the mechanisms underlying cellulases biosynthesis and secretion in T. reesei, as well as enzymatic cellulose hydrolysis. However, many unknowns still hinder the rational design of strains for robust cellulase production, with an optimized ratio of cellulolytic enzymes to reduce the required dosage for cellulose hydrolysis. Moreover, large-scale cellulase production relies on submerged fermentation, which suffers from several mass transfer limitations. As the mycelia grow, the fermentation broth rapidly develops non-Newtonian properties, necessitating energy-intensive mixing and aeration to facilitate oxygen transfer essential for strain growth. Herein, this paper critically reviews updated progress in these regards, highlights challenges, and outlines potential solutions.