Second generation ethanol production from aguapé (Eichhornia crassipes)

The water hyacinth is an aquatic macrophyte plant considered as lignocellulosic biomass. The chemical composition of the water hyacinth is presented in considerable contents of cellulose and hemicellulose, and low levels of lignin, which constitutes a potential substrate for the production of ethanol. The present study aims to develop a technology for the production of ethanol of the second generation from the biomass of aguapé. To reach the proposed objectives, the chemical characterization of the aguapé biomass was carried out afterward, acid and alkaline pretreatment stages, optimization of the pretreatment acid saccharification, fermentation, and distillation. Initially, the centesimal composition of the aguapé was determined, indicating the presence of 32.50% cellulose, 28.61% hemicellulose and 7.46% lignin. Among the different forms of pre-treatment analyzed, the acid pretreatment presented a better performance in the saccharification process, presenting approximately 46.16% yield in the conversion of reducing sugars. The optimization of the acid pretreatment was applied a Factorial Planning through a central rotational compound design. The STATISTICA Version 8.0 program (Statsoft Inc., Tulsa,) was used for data analysis. Pretreatment with dilute sulfuric acid resulted in the removal of at least 81% of the hemicellulose present in the water and 87% of the conversion of reducing sugars. The Saccharification and Separate Fermentation showed higher efficiency compared to the Saccharification and Simultaneous Fermentation process, presenting better conversion of sugars using the Cellic CTec2® enzymatic cocktail. The enzymatic hydrolyzate submitted to Saccharification and Separated Fermentation with Saccharomyces cerevisiae presented a YP/S of 0.50 with 2.62 g/L of alcohol in the fermented mash. The obtained data indicated that the evaluated aguapé presents a high potential for the production of second-generation ethanol.