Isolation of a cellulase hyperproducing mutant strain of Trichoderma reesei

Trichoderma reesei has been employed as a commercial cellulase producer; however, the cellulase obtained has low β-glucosidase activity. Lactose is a promising cellulase inducer because it is easy to be dissolved, but its induction efficiency is lower than that of solid inducers, such as biomass. We aimed to obtain a cellulase-producing strain that is compatible to on-site production, and developed a cellulase hyperproducing mutant, T. reesei T1281, through repeated random mutagenesis. Protein quantification using Bradford method showed that T1281 produced 35.4 g/L (119 g/L using Lowry method) protein in 212 h. Moreover, T1281 exhibited the highest filter paper unit (15.6 U/mL) and β-glucosidase (53.8 U/mL) activity on lactose among the strains developed using random mutagenesis. Enzymes produced by T1281 hydrolyzed biomass into glucose and xylose without cellobiose and xylobiose accumulation, indicating that T1281 can be a potential ideal strain for industrial cellulase production. [Display omitted] •Trichoderma reesei T1281 was developed thorough random mutagenesis.•T. reesei T1281 produced 119 g/L of protein on lactose in 212 h.•High FPU (15.6 U/mL) and β-glucosidase (53.8 U/mL) levels were achieved.•Neither cellobiose nor xylobiose accumulated during biomass hydrolysis.