Enzymatic hydrolysates of Agave tequilana bagasse pretreated with protic ionic liquids: Saccharification efficiency and hydrogen production

Abstract

This work demonstrated for the first time that hydrogen (H2) can be generated from Agave tequilana bagasse (ATB) after ionic liquid (IL) pretreatment up to 111.1 L H2/kg hydrolyzed biomass in only 20 h. It is shown that the low-cost protic IL [EOA][OAc] (ethanolamine acetate) can effectively pretreat ATB at two different scales (bench and lab) using 2 and 250 g (dry basis) at 20% solids loading and 160 °C for 90 min resulting in significant structural changes followed by FTIR spectroscopy. The lignin content of the pretreated ATB was reduced by 28.6% after lab-scale pretreatment which ultimately improved the sugar yield with the different saccharification strategies (batch vs. fed-batch). Up to 0.643 g TS (total sugars)/g ATB were obtained in a fed-batch strategy with fixed enzymatic loading, representing an enhancing 2.8-fold when compared to the untreated biomass. Models of enzymatic saccharifications were included for both, untreated and pretreated ATB, in terms of TS concentration (g/L) and fiber length (mm) to confirm differences in accessibility and availability of both substrates. The results successfully revealed that 1.1 kg or 14 m3 of H2 can be produced from 100 kg of dry ATB after pretreatment with [EOA][OAc] indicating the feasibility of improved sugar and H2 yields where either a low-cost pretreatment agent or an adequate saccharification strategy contributes to the biorefinery scheme.