The production of cellulase in a spouted bed fermentor using cells immobilized in biomass support particles

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Abstract
Continuous cellulase production by Trichoderma viride QM 9123, immobilized in 6 mm diameter, spherical, stainless steel biomass support particles, has been achieved using a medium containing glucose as the main carbon source. Experiments were carried out in a 10‐L spouted bed fermentor. In this type of reactor‐recycled broth is used to create a jet at the base of a bed of particles, causing the particles to spout and circulate. During the circulation, particles pass through a region of high shear near the jet inlet. This effectively prevents a buildup of excess biomass and thus enables steady‐state conditions to be achieved during continuous operation. Continuous production of cellulase was achieved at significantly higher yield and productivity than in conventional systems. At a dilution rate of 0.15 h−1 (nominal washout rate for freely suspended cells is 0.012 h−1), the yield of cellulase on glucose was 31% higher than that measured during batch operation, while the volumetric productivity (31.5 FPA U/L· h) was 53% greater than in the batch system. The specific cellulase productivity of the immobilized cells was more than 3 times that of freely suspended cells, showing that diffusional limitations can be beneficial. This offers significant opportunity for the further development of biomass support particles and associated bioreactors.