High-level expression of a thermostable endo-β-1,3-glucanase from Trichoderma harzianum in Pichia pastoris KM71 and its use in the enzymatic hydrolysis of multifunctional oligoglucosides

Abstract β-1,3-oligoglucoside is widely used as a functional food additive and a physiologically active compound. To efficiently produce β-1,3-oligoglucosides through curdlan hydrolysis, the endo-β-1,3-glucanase gene from Trichoderma harzianum was expressed in Pichia pastoris KM71 for the first time in order to construct a high-yield endo-β-1,3-glucanase strain. Optimal conditions for cell culture and endo-β-1,3-glucanase induction were subsequently determined in shake flask experiments. Recombinant endo-β-1,3-glucanase activity was then evaluated in a 7 L bioreactor, reaching a maximum of 198.57 U/mL after of 118 h fermentation. The recombinant endo-β-1,3-glucanase optimally functioned at pH 5.5 and 50 °C in addition to being stable over a pH range of 4.0–6.0 and a temperature range of 30 °C – 50 °C. In addition, the expressed glucanase could efficiently hydrolyze scleroglucan and schizophyllan to produce branched oligoglucosides exhibiting different degrees of polymerization (DP 3–10) and structures. The high enzyme activity and specificity towards polysaccharides with β-1,3-linked glucose residues as primary chains renders recombinant endo-β-1,3-glucanase an ideal candidate enzyme for the industrial production of oligoglucosides.