Batch Fermentation of Lignocellulosic Elephant Grass Biomass for 2G Ethanol and Xylitol Production

Abstract

The solid and growing demand for fuels evidences the necessity of diversifying the countries’ energy matrices. The present work proposed to carry out pretreatment tests, enzymatic hydrolysis, and batch fermentation of elephant grass biomass — a competitive lignocellulosic culture for obtaining ethanol due to low production costs and high levels of agricultural productivity. As a process and product economy strategy, the production of xylitol integrated with ethanol production was carried out. Therefore, two alkaline pretreatment methodologies were followed by enzymatic hydrolysis to obtain fermentable sugars. The pretreatments proved efficient in making cellulose available and removing the lignin content. The hydrolysates obtained showed 19.9 and 25.6 g/L of total sugars. Then, three fermentation conditions were carried out in each hydrolysate: (i) by the wild yeast strain Meyerozyma caribbica CHAP-096, (ii) by the industrial strain Saccharomyces cerevisiae PE-02, and (iii) by a combination of both yeasts in a 1:1 (v/v) ratio. A high ethanol yield of 0.42 g_ethanol/g_glucose was reached through the combination of S. cerevisiae and M. caribbica strains, representing 83% of the maximum theoretical yield (0.511 g_ethanol/g_glucose). The industrial strain S. cerevisiae PE-2 was also able to reduce xylose into another important component in biorefinery, xylitol, with a yield of up to 0.61 g_xylitol/g_xylose.

Graphical Abstract