Estratégias de reuso de micélio de Penicillium echinulatum e de Trichoderma reesei em cultivo sólido para a produção de celulases e xilanases

Abstract

The usage of lignocellulosic biomass for second-generation ethanol production is the target of many studies in Biotechnology. One of the bottlenecks to the wide application of this technology lays on the difficulty of developing economically viable and efficient enzymatic cocktails. Two genres of filamentous fungi are related on literature as great producers of the cellulolytic and hemicellulolytic complex: Penicillium and Trichoderma. With the goal of reducing debris generated during the microorganism cultivation and time of enzyme production on solid state cultivation, as well as increasing enzymatic activities, a strategy of reusing substrate and fungal mycelium was proposed. The system of mycelium and substrate reuse in solid state cultivation consists of the utilization of one microorganism inoculum for each fungus, and subsequent utilization of substrate and its mycelium for the enzyme production. Therefore, only one inoculum of the microorganisms and raw material usage was made to proportionate a longer cultivation and enzymatic production. The cultivations were conducted in cycles of enzymatic extraction with nutrient reposition in a syringe-type bioreactor. The tested cultivation medium included eucalyptus pretreated by steam explosion, rice bran, soy bran and mineral solution. Initially, a growth and enzymatic production analysis of P. echinulatum and T. reesei was carried out through eight cultivation days in order to define the initial enzymatic extraction day. After that, different formulations of nutrient reposition were tested: addition of mineral solution, addition of a mixture of cultivation medium, and addition of the mixture and mineral solution. Having defined the best condition of supplementation, different materials were used aiming the reduction of the culture medium compaction and promoting a better system aeration: polyurethane sponge, sugar cane bagasse and rice husk. Considering the enzymatic production kinetics, it was defined that the enzymatic extractions and nutrient reposition must be done in days 4, 7, 10 and 13 for P. echinulatum and 3, 5, 6 and 7 for T. reesei. The most promising supplementation and support were, respectively, the reposition of mineral solution and rice husk. In these conditions, enzymatic activities of FPA were five and two times bigger than the conventional production of these enzymes, respectively for P. echinulatum and T. reesei. Furthermore, xylanase titers of 1303 U.g-1 were registered by P. echinulatum at the end of the four extraction and reposition cycles. It has proved to be a promising strategy to reduce the cost, process time and debris, increasing significatively the enzymatic production of P. echinulatum and T. reesei. [resumo fornecido pelo autor]