Produção de enzimas celulolíticas e xilanolítica a partir do bagaço do sorgo sacarino por fermentação semissólida e submersa.

Abstract

Lignocellulosic materials are a rich source of cellulose, hemicellulose and lignin, and represent a promising and low-cost raw material for the production of enzymes. The demand for such catalysts has grown, encouraged mainly by the biofuel industry, especially for the production of 2nd generation ethanol. In this context, the objective of this work was to study the production of cellulolytic enzymes (CMCase and FPase) and xylanolitic (Xylanase) from semisolid (FSS) and submerged (FSm) fermentation using the sweet sorghum bagasse variety IPA P15 as a substrate and inducing source the wheat bran and metabolizing microorganism Trichoderma reesei LCB 48. Characterizations of the substrates, bagasse of sweet sorghum (BSS) and wheat bran (FT) were carried out, and desorption isotherms were constructed for these substrates. For the study of the production of CMCase, FPase and Xylanase enzymes by fermentative processes, an experimental planning 22 with 3 central points was carried out, analyzing the influence of the variables initial moisture and the wheat bran content in the FSS and FSm the influence of the content of wheat bran and mass/volume ratio (m/v) of the substrate concentration and for each experimental condition, kinetic monitoring of the fermentation was carried out for 240 hours. For the optimal condition of the experimental planning in the FSS, an increase in scale was carried out to analyze the influence of this increase in the studied enzymatic activities. The characterization of BSS demonstrated that this is a substrate with the potential to be used in fermentation for the production of cellulases and xylanase, as it presents 40,5 % and 30,5 % cellulose and hemicellulose, respectively. The substrate desorption isotherms showed a correlation between water activity and equilibrium humidity for the substrates. The GAB model provided a good fit for the experimental data from substrate, and the monolayer moisture values for each substrate. The statistical treatment of the planning at a 95 % significance level, showed that the variables initial moisture and wheat bran content influenced the enzymatic activities of CMCase, FPase and Xylanase in FSS, and the variables wheat bran content and the mass/volume (m/v) ratio of the substrate concentration influenced enzyme activities in FSm. The results obtained in the study of the production of these enzymes by FSS pointed to the assay carried out with 60 % humidity and 50 % FT in the composition of the substrate, which showed the highest enzymatic activities for all the studied enzymes. Xylanase activity peaked at 548,7 U.g-1 in 48 hours, CMCase peaked at 19,6 U.g-1 in 72 hours, and FPase peaked at 2,1 U.g-1 in 96 hours of the process. The results obtained in FSm, on the other hand, showed the assay carried out with 5 % of the substrate concentration and 50 % of FT, which showed the highest enzymatic activities for all the studied enzymes. Xylanase activity peaked at 76,7 U.mL-1 in 192 hours and CMCase peaked at 1,5 U.mL-1 in 216 hours. The activity peaks occurred at different times, which makes it easier to obtain the different enzymes in a single process. The greatest enzymatic activities found were for the scale increase performed with 30 g of substrate and 500 mL capacity of the bioreactor in the FSS, where peaks of 24,7 U.g-1 (3,3 U.mL-1) were obtained of CMCase, 2,8 U.g-1 (0,4 U.mL-1) of FPase and 708,9 Ug-1 (94,5 U.mL-1) of Xylanase.