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Lactose (1,4-O-β-d-galacto-pyranosyl-d-glucose) induces cellulolytic enzymes in Trichoderma reesei and is in fact one of the most important soluble carbon sources used to produce cellulases on an industrial level. The mechanism underlying the induction is, however, not fully understood. In this study, we investigated the cellular functions of the intracellular β-glucosidases CEL1a and CEL1b in the induction of cellulase genes by lactose in T. reesei. We demonstrated that while CEL1a and CEL1b were functionally equivalent in mediating the induction, the simultaneous absence of these intracellular β-glucosidases abolished cbh1 gene expression on lactose. d-Galactose restored the efficient cellulase gene induction in the Δcel1a strain independently of its reductive metabolism, but not in the Δcel1a Δcel1b strain. A further comparison of the transcriptional responses of the Δcel1a Δcel1b strain complemented with wild-type CEL1a or a catalytically inactive CEL1a version and the Δcel1a strain constitutively expressing CEL1a or the Kluyveromyces lactis β-galactosidase LAC4 showed that both the CEL1a protein and its glycoside hydrolytic activity were indispensable for cellulase induction by lactose. We also present evidence that intracellular β-glucosidase-mediated lactose induction is further conveyed to XYR1 to ensure the efficiently induced expression of cellulase genes., (Copyright © 2014, American Society for Microbiology. All Rights Reserved.)

The production of beta-1,3-glucanases and chitinases by three strains of Trichoderma in submerged cultures was determined. The synthesis of enzymes was induced by cell wall biopolymers of phytopathogenic fungi (Botrytis cinerea, Fusarium culmorum and F. oxysporum). T. hamatum produced the highest beta-1,3-glucanase activity; the most effective inducer of enzyme synthesis was the biomass of F. oxysporum. All examined strains of Trichoderma inhibited phytopathogen growth in biotic tests. The diffusion tests showed that the lytic enzymes take part in growth inhibition of phytopathogenic fungi.

Of 24 Trichoderma isolates, T harzianum Rifai (T24) showed a potential for control of the phytopathogenic basidiomycete Sclerotium rolfsii. When T24 was grown on different carbon sources, growth inhibition of S. rolfsii by the T24 culture filtrate correlated with the activity of extracellular chitinase and beta-1,3-glucanase. The 43-kilodalton (kDa) chitinase and the 74-kDa beta-1,3-glucanase were purified from the T24 culture filtrate in two and three steps, respectively, using ammonium sulphate precipitation followed by hydrophobic interaction chromatography (phenyl-Sepharose) and gel filtration (beta-1,3-glucanase). Km and Kcat were 3.8 g l(-1) and 0.71 s(-1) for the chitinase (chitin) and 1.1 g(-1) and 52 s(-1) for the beta-1,3-glucanase (laminarin). The chitinase showed higher activity on chitin than on less-acetylated substrate analogues (chitosan), while the beta-1,3-glucanase was specific for beta-1,3-linkages in polysaccharides. Both enzymes were stable at 30 degrees C, while at 60 degrees C the chitinase and the beta-1,3-glucanase were rapidly inactivated, showing half-lives of 15 and 20 min, respectively. The enzymes inhibited growth of S. rolfsii in an additive manner showing a promising ED50 (50% effective dose) value of 2.7 microg/ml.

We have used a targeted gene deletion event to remove the coding region for the bgl1 gene encoding an extracellular beta-glucosidase from the genome of the cellulolytic fungus Trichoderma reesei. The bgl1 null mutants were used to investigate the role of beta-glucosidase in the hydrolysis of cellulose and induction of the other cellulolytic enzyme components. In the absence of extracellular beta-glucosidase, growth of bgl1 null strains on several carbon sources was the same as that of the parent (as measured by mycelial dry weight). However, levels of extracellular protein and total endoglucanase production were seen to lag relative to those levels observed in the control strain. The mRNA levels of the CBHI, CBHII, EGI, and EGII cellulase genes (cbh1, cbh2, egl1 and egl3) showed a corresponding lag in induction, suggesting that the absence of extracellular beta-glucosidase has an effect on the co-ordinate regulation of the other cellulase genes at the level of transcription. The addition of a potent inducer of the cellulase complex (sophorose) resulted in normal rates of cellulase gene mRNA production and extracellular protein release. This indicates that the absence of beta-glucosidase is not affecting some intrinsic cellular ability to produce mRNA or secrete protein. These data suggest that a functional beta-glucosidase is at least partially responsible for the efficient induction of the depolymerase enzymes of the cellulase complex. The observation that the cellulase complex is induced, albeit after a lag, suggests that other enzymes are present that can substitute for the function of beta-glucosidase during induction.