Enhanced Bioethanol Production from Blue Agave Bagasse in a Combined Extrusion–Saccharification Process Carmina Montiel 1 & Oscar Hernández-Meléndez 2 & Eduardo Vivaldo-Lima 2 & Martín Hernández-Luna 2 & Eduardo Bárzana 1 # Springer Science+Business Media New York 2016 Abstract This paper describes an improved process for bioethanol production using a recently developed combined extrusion–saccharification technology. Blue agave bagasse (BAB) was pretreated via a thermo-mechano-chemical pro- cess (co-rotational twin-screw, reactive extrusion) to increase the availability of cellulose and hemicellulose for enzymatic saccharification. Then, several commercial enzyme prepara- tions, boosted with accessory enzymes (exoglucanase, endoglucanase, hemicellulase, xylanase, and β-glucosidase), were tested with extruded BAB at 5 % consistency in a stirred vessel. The enzyme blend that produced the highest saccharification yield was evaluated at different BAB consistencies. The obtained concentration of sugars increased up to 69.5 g/L (73 % yield) when a 20 % BAB mixture was used. When the enzyme blend was fed into the extruder and with a residence time of 2 min, the yield reached 15 % of the maximum theoretical of C6 sugars along this step. This extruded and pre-saccharified BAB was further hydrolyzed and used for fermentation. The pre-saccharification step significantly enhanced cellulose degradation and ethanol production. Our results indicate that the enzymatic saccharification of BAB, coupled with reactive extrusion, produces an excellent substrate for bioethanol production. Keywords Bioethanol production . Lignocellulosic materials . Cellulose degradation . Cellulases . Bioextrusion . Enzymatic hydrolysis Introduction Currently, the continuous depletion of fossil fuels and the need to reduce greenhouse gas emissions to mitigate global warming have generated an increasing worldwide interest in alternative energy sources. Developing biofuels from bio- masses is one alternative. In particular, producing bioethanol from lignocellulosic biomasses has emerged as an alternative fuel source that can decrease the depletion of crude oil and alleviate environmental pollution. Countries around the world are interested in the potential of lignocellulosic biomasses as promising feedstocks for ethanol production due to their low cost and wide availability [1]. However, combining effective pretreatment processes with efficient enzymatic hydrolysis to obtain fermentable sugars from lignocellulosic residues remains a major challenge. Blue agave bagasse (BAB) is a lignocellulosic by-product in the production of tequila, the most important alcoholic beverage produced in Mexico. The annual production of BAB in Mexico is approximately 300 Mton, which represents approximately 40 % of the agave plant [2]. BAB is currently used as animal feed or for composting. However, its potential for saccharification and subsequent bioethanol production has been barely explored. Tequila is produced from Agave tequilana, a plant commonly known as blue agave. Middle- aged agave plants are collected, the leaves removed, and the pinecones cooked in the tequila production process. The juices * Carmina Montiel carmina@unam.mx * Eduardo Bárzana ebg@unam.mx 1 Departamento de Alimentos y Biotecnología, Facultad de Química, Universidad Nacional Autónoma de México, 04510 Mexico City, Mexico 2 Departamento de Ingeniería Química, Facultad de Química, Universidad Nacional Autónoma de México, 04510 Mexico City, Mexico Bioenerg. Res. DOI 10.1007/s12155-016-9747-x