Enzyme optimization and fermentation of high solids loading AFEX pretreated agave residues for ethanol production

Evaluation of regionally-important agroindustrial residues as potential feedstocks for sustainable liquid biofuel production is important to avoid potential negative environmental impacts, and  also to promote regional economic development. Agave tequilana and A. salmianaare two agave species of great economic importance in Mexico.

Continuing with our past work to develop appropriate enzyme mixtures to hydrolyze agave residues (bagasse and leaf fibers), we used the optimum AFEX^TMpretreatment parameters, and the appropriate enzyme cocktails (Flores, et al. 2014) to investigate the relationship between total solids loading, enzyme loading and time in order to improve the saccharification yields for this biomass. At higher glucan and enzyme loadings, a higher concentration of monomeric sugars is released, however the sugar conversion yields follow a different pattern.

For the bioethanol fermentation test, we evaluated the effect of the total solids loading on the growth potential of Saccharomyces cerevisiae424A (LNH ST) using separate hydrolysis and fermentation (SHF) mode, with and without nutrient supplementation. Based on these experiments, we selected a solids loading that yields both high sugar conversion and high ethanol metabolic yield to test the yeast under simultaneous saccharification and cofermentation (SSCF) operation.

AFEX is a registered trademark of MBI, Lansing, Michigan.