Produção de celulases por Penicillium sp. FSDE15 e hidrólise enzimática do sabugo de milho

Abstract

Given the world scenario, where more and more waste is generated by the various sectors of industry and agriculture, special attention has been given to the reuse of these materials, such as corncob and straw and wheat bran. One of the alternatives is the production of products with high added value, such as enzymes, using these residues as substrates. Among the various enzymes, cellulases stand out (CMCases, FPases and -glucosidases), capable of converting part of the lignocellulosic biomass into fermentable sugars, which can be converted into cellulosic or second-generation ethanol. Therefore, this study aimed to produce cellulase enzymes through the filamentous fungus Penicillium sp. FSDE15, to carry out the enzymatic hydrolysis of the pretreated corncob aiming at the release of fermentable sugars for the production of second-generation ethanol. Initially, the pretreatment of the corncob was carried out. Three types of pre-treatment were applied, one acid, one alkaline and one hydrothermal. The conditions applied to each type of pretreatment were established from an experimental factorial design. In the case of chemical pretreatments, a 23 planning was used with three repetitions at the central point, varying the time (10, 40 and 70 min), temperature (40, 70 and 100 ⁰C) and reagent concentration (1, 2 and 3%). The hydrothermal pretreatment was carried out following an experimental factorial design of 22 with three replications in the central point, varying the time and temperature, using the same interval as that applied to the chemical pretreatments. Through fermentation tests (60% moisture, ambient temperature and spore concentration of 106 spores/mL), it was possible to obtain a maximum production of CMCase and FPase of 21.11 U/g and 1.29 U/g, respectively, in 216 h of fermentation, for cultivation carried out with wheat bran and corncob in the proportion of 50%. The -glucosidase activity reached its peak of 8.72 U/g in 216 h for cultivation carried out with pure wheat bran. In the results of enzymatic hydrolysis of corncob pretreated with H2SO4, a concentration of reducing sugars of 23.07 g/L of glucose was reached for hydrolysis with the enzymatic extract of Penicillium sp. FSDE15 and 47.62 g/L for hydrolysis using the commercial enzyme Celluclast®. For the corncob pretreated with NaOH, it was possible to obtain concentrations of 45.55 and 74.12 g/L of glucose for hydrolysis using the enzymatic extract and commercial cellulase, respectively. As for the hydrothermally pretreated corncob, 25.77 g/L of glucose were obtained for hydrolysis with the Penicillium extract and 21.34 g/L for the Celluclast® enzyme. All the best reducing sugar values were reached within 48 h of hydrolysis. These results, together with the study of scale-up for the production of bioethanol, demonstrate that the hydrothermally pretreated corncob, combined with the enzymatic extract produced by Penicillium sp. FSDE15, has great potential for the production of second generation ethanol.