Acid pretreatment optimization for xylose production from Agave tequilana Weber var. azul, Agave americana var. oaxacensis, Agave karwinskii, and Agave potatorum bagasses using a Box-Behnken design

Abstract

There is a growing interest in the use of lignocellulosic biomass for biofuel production leading to by-products with high added value such as xylitol, a sweetener obtained from chemical synthesis or fermentative pathways, characterized by high degree of sweetness, recommended for people with diabetes, making it a product of great interest in the industrial market. The objective of this study was to use the bagasse of four agave plants from Mexico: Agave tequilana Weber var. azul (AT), Agave Americana var. oaxacensis (AA), Agave karwinskii (AK), and Agave potatorum (AP) to obtain xylose as an alternative for xylitol or ethanol production. The dilute acid pretreatment was optimized to obtain the maximum concentration of xylose and the minimum concentration of acetic acid, using a Box-Behnken design, where H2SO4 concentration, hydrolysis time, and liquid-to-solid ratio were evaluated. Xylose concentrations of 23.18 g/L (AT), 27.63 g/L (AA), 31.8 g/L (AK), and 24.42 g/L (AP) were achieved. It was also observed that by using more concentrated H2SO4 solutions, higher concentrations of xylose were obtained, but also high concentrations of acetic acid (1.02 g/L in AT, 2.3 g/L in AA, 3.46 g/L in AK, and 2.01 g/L in AP). This study shows that AT, AA, AK, and AP are a promising alternative feedstock for bioethanol or xylitol production using xylose as substrate.