Comparação da produção de etanol 2G por bioprocessamento consolidado a partir de bagaço e palha da cana

Abstract

Given the current scenario marked by the dominance of fossil fuels, the search for highly efficient renewable energy sources is growing more and more. One alternative is to make better use of lignocellulosic materials from sugarcane to produce second-generation ethanol (2G). One of the challenges of this process is the efficient hydrolysis of biomass due to the high cost of hydrolytic enzymes, the complex structure of biomass and the fact that some of the cellulolytic enzymes adsorb onto the lignin contained in its structure, so that the type of biomass used can interfere with the efficiency of this process. Consolidated Bioprocessing (BPC), in turn, stands out as a technique in which enzyme production, biomass hydrolysis and sugar fermentation occur simultaneously in a single bioreactor using recombinant microorganisms. In this sense, the present study aimed to evaluate the BPC of different biomasses (bagasse and sugarcane straw), as well as different strategies to improve the efficiency of the hydrolysis stage and consequently the production of ethanol. For this purpose, the genetically modified yeast Saccharomyces cerevisiae AC14, which secretes seven hydrolytic enzymes, was used in the BPC of sugarcane straw and bagasse pretreated hydrothermally, both subjected to freezing to improve the access of enzymes to the biomass or to the addition of soybean protein as a strategy to bypass the adsorption of enzymes, acting as sacrificial molecules. The cultivation time was 12 hours, and to evaluate the results, analyses of yeast viability, optical density (OD), pH of the medium, enzymatic activity and quantification of substrates and products by high-performance liquid chromatography (HPLC) were performed. In general, the tests with both biomasses presented similar performance, with productivities around 1.2 g/L/h. Freezing favored crops using both biomasses, but the addition of soy protein favored only crops with straw, showing the influence of the type of biomass in the process. Thus, BPC represents an interesting alternative for the production of 2G ethanol, and freezing and the addition of soy protein are attractive methods to increase crop efficiency.