Production of ethanol and pullulan assisted by unconventional methods in sugarcane bagasse biorefineries: hydrodynamic cavitation reactors and use of visible light with different wavelengths

Abstract

The feasibility of sugarcane bagasse biorefineries requires the study of innovative alternatives with potential to improve the performance of the main steps of the developing processes, particularly in the pretreatment and biological stages, such as fermentation. Actually, pretreatment corresponds to a persistent bottleneck in biorefineries, and the development of continuous hydrodynamic cavitation reactors for this application is a completely new approach. In this project, the use of hydrodynamic cavitation for the alkaline pretreatment of sugarcane bagasse in a continuous reactor is proposed. The batch reactor available at the biotechnology department labs will be used in assays for optimization of process conditions, including temperature and the use of different types and concentrations of alkalis, besides different orifice plate configurations. Next, the system will be adapted for use in continuous mode, including a solid/liquid separation system. Operating conditions in continuous mode will then be evaluated and optimized. On another working line, the effect of the use of visible LED lights of different wavelengths will be evaluated, aiming to increase the productivity of the process or to change the quality of the obtained product. As study models, ethanol and pullulan were selected as products, this latter an exopolysaccharide of interest to the food and pharmaceutical industries and whose production may contribute to the overall viability of a biorefinery. Thus, the pretreated material will be enzymatically hydrolyzed and fermentations assisted by LED lights of different colors will be carried out in Erlenmeyer flasks for evaluation of the effect of the light wavelength and luminance in the system. After the optimization of process variables, tests in bench photobioreactors will be performed aiming to the evaluation of the possibility of scale up of the system. Execution of the project is expected to favor the development of national technology applicable to different stages of a biorefinery, thus favoring the development of sustainable and environmentally friendly processes of economic and social interest. (AU)