Saccharification of agave bagasse with Cellulase 50 XL is an effective alternative to highly specialized lignocellulosic enzymes for continuous hydrogen production

Abstract

Agave bagasse is the lignocellulosic residue of the tequila industry and a potential feedstock for hydrogen production (H2) via dark fermentation after proper saccharification. Highly specialized enzymes for hydrolysis of lignocellulosic biomass are costly, hindering their application in continuous processes. This work investigated the use of a generic cellulase (Cellulase 50 XL), to prepare the hydrolysates from agave bagasse, either alone or combined with a highly specialized hemicellulase (Viscozyme L). The combination of Cellulase 50 XL and Viscozyme L increased the release of both total carbohydrates and chemical oxygen demand (COD) in 28.5% and 22.2%, respectively compared with Cellulase 50 XL. Conversely, the maximum volumetric H2 production rate (VHPR, 9.9 L H2/L-d) reached with the Cellulase 50 XL hydrolysates in continuous stirred tank reactors at an organic loading rate of 100 g COD/L-d, is the highest VHPR reported so far with enzymatic agave bagasse hydrolysates obtained with non-specialized enzyme. The estimated cost of H2 production using Cellulase 50 XL at lab-scale was 0.7 USD/L H2. From a systematic comparison of H2 productivities and lab-scale costs with similar studies it was concluded that: i) the composition, and not only the concentration of total carbohydrates plays a critical role in the performance of H2 production, ii) Cellulase 50 XL was one of the best cost-effective alternatives despite being designed for food sectors and not for the hydrolysis of lignocellulosic biomass. Overall, considering H2 productivities and cost of H2 production, Cellulase 50 XL hydrolysates resulted an appropriate option for cost-effective continuous H2 production.