PRODUCTION OF TRICHODERMA CELLULASE IN LABORATORY AND PILOT SCALE

Trichoderma reesei mutants QM 9414, MCG 77, MCG 80, RUT C 30, CL-847, VTT-D, and SVG are the preferred microorganism for the production of a complete cellulase which can hydrolyze crystalline cellulose. All these strains secrete celluloytic proteins (exocellulases, endocellulases, and cellobiase) when they are grown on a mineral medium supplemented with pure cellulose (Solka Floc, cotton, Avicel) or pretreated lignocellulose (wood, straw). Some of the mutants produce cellulase with lactose as the sole carbon source. Submersed shake culture fermentations were mainly used for strain selection and preliminary optimization of culture conditions. Laboratory fermentations were performed in stirred tank reactors with volumes up to 3000 liters. On average, 250 mg of cellulase protein is formed per gram of metabolized carbon source, the enzyme has a specific activity of about 0.5 to 1.0 filter paper units per mg protein. The volumetric productivity rate is in the range of 50-150 FPU liter h-1. The enzyme concentration strongly depends on the substrate concentration and increases from 2-3 FPU ml-1 at 2% to 7-18 FPU ml-1 at 8%. High enzyme concentrations and volumetric rates are obtained by fed batch fermentations. If compared under identical conditions, all T. reesei mutants developed after 1978 show approximately the same capacity to produce cellulase. The very great differences reported in the literature result from modifications of the fermentation parameters and difficulties in objectively measuring the enzyme concentration FPU ml-1. On an industrial scale, Trichoderma cellulases are produced by solid state as well as by submersed fermentation. A list of commercially available cellulases and their potential application is given. If compared on a protein base (mg cellulase protein g-1 cellulose), the different cellulases show very different capacities for hydrolyzing cellulose.