Produção de celulases e xilanases por Penicillium echinulatum em processo submerso utilizando biorreatores com agitação mecânica e airlift de circulação interna

Abstract

Cellulolytic enzymes have many uses, particularly in the food, textile, and paper industries. However, their major potential use is in the hydrolysis of cellulose a component of lignocellulosic residues for ethanol fuel production. Among the cellulase-producing microorganisms, mutants of the Trichoderma genus are the most studied and most widely used in the industry. Penicillium echinulatum mutants are also among those microorganisms currently being studied for cellulase production. The present study provides data on cellulase production by P. echinulatum in submerged culture in flasks under agitation and in stirred tank and internal circulation airlift bioreactors, in the presence of cellulose and sorbitol. Medium composition and supplementation timing of inducers and carbon sources, initially for flasks under agitation, were also studied. Assay conditions showing the best results in flasks were tested in bioreactors with mechanical agitation and airlift. Hydrodynamic conditions, such as flow speed and aeration in airlift bioreactor for cellulase production optimization, as well as medium formulations in bioreactor with mechanical agitation, with oxygen maintained at a minimum 20% saturation level, were studied. Enzymatic analyses of FPA (filter paper activity), β-glucosidase, endogluconase, and xylanase; biomass concentration; carbon source consumption; and pH variation were used as evaluation indicators. Results obtained in flasks under agitation showed that sorbitol might be used as a partial substitute of cellulose, in favor of enzymatic production and cultivation rheology. It was further observed that cellulose supplementation influences the enzymatic production in submerged cultures, and that lactose in association with sorbitol produces higher enzymatic titers. With regard to bioreactors, the best results were obtained with the airlift bioreactor for a medium containing 0.25% (w/v) sorbitol and 0.75% (w/v) cellulose, when compared to the bioreactor with mechanical agitation. Assays with 3-phase supplementation did not show any relevant results with regard to enzymatic production and volumetric productivity. Assays initiated with sorbitol and supplemented with cellulose showed better results when compared to those conducted in the batch-production model. Assays initiated with 0.25% (w/v) sorbitol showed higher volumetric productivity compared to those initiated with 1% (w/v) sorbitol. It was found that cellulose might be replaced by sugar cane bagasse, a low-cost and readily available source of insoluble carbon.