Use of waste generated in agro-industrial processes in the mezcal industry

Abstract

Mezcal is a traditional Mexican alcoholic beverage made through the fermentation of agave cenizo (Agave durangensis), for which an annual demand of 1,200,000 tons is estimated in Mexico, generating approximately 480,000 tons of bagasse waste per year. This poses an environmental problem. The recovery of fermentable reducing carbohydrates from the bagasse to obtain ethanol is an innovative option. In this research, three types of hydrolysis (acidic, enzymatic, and acid-enzymatic) were developed on the residual bagasse from mezcal production, aiming for the highest possible concentration of reducing sugars. Acid hydrolysis was carried out with HCl at three different pH values and three different times, yielding a maximum concentration of 13.03 g/L. In enzymatic hydrolysis, cellulase enzymes were used with three different bagasse-enzyme ratios, keeping time and temperature constant, showing a maximum concentration of reducing carbohydrates of 8.46 g/L. Acid-enzymatic hydrolysis used the acid hydrolysis with lower carbohydrate production (2.2 g/L), and three different enzyme concentrations were added while maintaining constant temperature and time, resulting in a concentration of 4.8 g/L. Finally, the highest concentration of reducing carbohydrates was fermented for 7 days using baker's yeast, and after distillation, 96% v/v ethanol was obtained. The results of this research suggest that agave bagasse hydrolysis could be considered an alternative for obtaining a usable energy vector on an industrial scale.