Promotion of extracellular lignocellulolytic enzymes production by restraining the intracellular β-glucosidase in Penicillium decumbens

• Three β-glucosidase-lacking mutants of P. decumbens 114-2 were constructed.
• Deletion of bgl2 enabled significantly increased production of lignocellulolytic enzymes.
• The increased production of lignocellulolytic enzymes was due to accumulation of intracellular cellobiose.
• Cellobiose was the direct inducer of cellulase in P. decumbens.

In this study, the functions of β-glucosidases in regulation of the lignocellulolytic enzymes production in Penicillium decumbens 114-2 were investigated. The major extracellular β-glucosidase gene bgl1 and the major intracellular β-glucosidase gene bgl2 were deleted in P. decumbens 114-2 respectively. In Δbgl2, the production of extracellular lignocellulolytic enzymes (including endoglucanases, cellobiohydrolases and xylanases) on insoluble cellulose was significantly promoted, while in Δbgl1 there was no any difference compared with that of 114-2. The enhancement of the production of lignocellulolytic enzymes in Δbgl2 was likely attributed to the accumulation of intracellular cellobiose. Induction experiment in Δbgl1Δbgl2 showed that cellobiose was an inducer of lignocellulolytic enzymes expression in P. decumbens 114-2, and the induction was unrelated to the formation, if any, of gentiobiose or sophorose from cellobiose.