Evaluation of 2G ethanol production from sugarcane bagasse pretreated by hydrodynamic cavitation-assisted oxidative process: pretreatment conditions and utilization of simultaneous hydrolysis and fermentation reactors with interconnected columns system

Abstract

In Brazil, the development of processes for ethanol production from sugarcane bagasse has great relevance. However, the economic viability of 2G ethanol production requires the integral utilization of raw material in the biorefinery context, with important research directed to the production of alcohol from glucose present in cellulosic enzymatic hydrolysates. Nevertheless, the hemicellulosic fraction represents one-third of the bagasse's biomass and it can be hydrolyzed to pentoses, which can be converted to ethanol using specific yeasts. The utilization of the biomass carbohydrates has been performed using an initial step of pretreatment. This step corresponds to a persistent bottleneck in the process; however, it is necessary to enhance the enzymatic digestibility of cellulose for the subsequent hydrolysis stage. Different alternatives have been researched and, recently, pretreatment methods assisted by hydrodynamic cavitation (HC) were evaluated, showing promising results. Regarding the posterior steps of hydrolysis and fermentation, they can be carried out in separated or in simultaneous reactors. In the last case, if there is co-fermentation of C5 and C6 sugars, the process is called Simultaneous Saccharification and co-Fermentation (SSCF). In this project, the development of a pretreatment process of sugarcane bagasse with oxidative processes assisted by HC, in presence of acids and Iron salts, is proposed. Besides, the utilization of the pretreated material in the production of ethanol in an SSCF with an interconnected columns system will be evaluated. Firstly, sugarcane bagasse will be characterized and pretreated. Then, the solid material obtained in the pretreatment will be used in the SSCF system with interconnected column reactors. The enzymatic hydrolysis of the biomass will occur in one column, while the other column reactor will contain yeast cells immobilized on a gel of calcium alginate. The production of ethanol will be evaluated using Scheffersomyces shehatae cells. Therefore, the project contributes to innovative approaches for the vitalization of bioprocesses of interest for the integral utilization of lignocellulosic raw materials, resulting in the generation of national sustainable technology. (AU)