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Agave lechuguilla is a common plant of Northern Mexico that can be used as feedstock in the context of a biorefinery without competition for food use. In this work, the production of fermentable sugars from this biomass has been studied for the first time using dilute sulfuric acid pretreatment. An experimental design and response surface methodology were applied with temperature (160–200 °C) and acid concentration (0.5–1.5% w/v) chosen as factors. The pretreatment conditions were expressed in a combined severity factor, which ranged from −0.75 to 2.38. According to an optimization criterion that maximizes hemicellulosic sugar recovery in the prehydrolysate and glucose recovery by enzymatic hydrolysis, optimal conditions for acid pretreatment of agave were found to be 180 °C and 1.24% (w/v) H2SO4 at 10% biomass loading. These optimal conditions yielded 87% hemicellulosic sugar recovery and 68 g glucose/100 g glucose in raw agave. The whole slurry resulting from acid pretreatment of agave at optimal conditions was enzymatically saccharified yielding a sugar solution that was co-fermented by the ethanologenic Escherichia coli MM160. This process configuration allowed the fermentation of all sugars in raw A. lechuguilla in a single step reaching an ethanol yield of 73.3%.

Different strategies were assessed for the production of ethanol from Agave lechuguilla that was pretreated by autohydrolysis. Separate hydrolysis and fermentation (SHF) was compared against simultaneous processes including simultaneous saccharification and fermentation (SSF) and prehydrolysis and simultaneous saccharification and fermentation (PSSF) using different solids (15%, 20%, and 25% w/w) and enzyme loadings (15 FPU/g, 20 FPU/g, and 25 FPU/g glucan). The results showed that the maximum ethanol concentration (53.7 g/L) and productivity (1.49 g/L h-1) was obtained at 36 h in the SHF configuration at the highest solids and enzyme loadings (25% w/v and 25 FPU/g glucan, respectively). The ethanol concentration and productivity obtained in the PSSF configuration at the same time were 45 g/L and 1.25 g/L h-1, respectively. The SSF configuration exhibited the lowest ethanol concentration and productivity (10.4 g/L and 0.29 g/L h-1, respectively) at 36 h. The enzyme used, Cellic CTec3, allowed for high glucose yields at the lower enzyme dosage assessed. The SHF configuration exhibited the best results. However, the PSSF configuration can be considered an attractive alternative because it eliminated the need for solid-liquid separation devices, which simplifies the industrial implementation of the process.