Multi-stage glucose/pachymaran co-feeding enhanced endo-β-1,3-glucanase production by Trichoderma harzianum via simultaneous increases in cell concentration and inductive effect

Endo-β-1,3-glucanase is used to hydrolyze curdlan in a wide range of oligosaccharides production processes. Using pachymaran as the sole carbon source resulted in an endo-β-1,3-glucanase activity of 86.1 U/mL and an E endo / E total ratio of 0.43, which were 3.2 and 1.65 folds of the values from control (glucose as the sole carbon source), due to the inductive effect of pachymaran as a polysaccharide. However, the cell concentration decreased from 25 to 12 g/L during the late fermentation phase. Therefore, a novel multi-stage feeding strategy was developed wherein glucose was fed twice during the cell logarithmic growth phase (24 and 48 h) and pachymaran once during the early stage of the enzyme accumulation phase (72 h). Consequently, the cell concentration remained around 30 g/L during the late fermentation phase. Endo-β-1,3-glucanase activity and E endo / E total reached 160.0 U/mL and 0.76, respectively, which were 6.0 and 2.92 folds of the values from control. In addition, three typical polysaccharides with β-1,3-linked glucose residues were successfully hydrolyzed by endo-β-1,3-glucanase to produce multifunctional β-1,3-oligoglucosides.