Ozonation of tannic acid to model biomass pretreatment for bioethanol production

Lignocellulosic biomass is a promising feedstock for ethanol production, but lignin, a polyphenol, hampers the use of enzymes for its saccharification; pretreatment is thus key to preparing such feedstock. Ozonation was previously demonstrated as an effective pretreatment, but claimed to be uneconomical due to the assumed need for lignin mineralization. We analyzed, for the first time, ozonation of highly concentrated tannic acid (TA) solution (60 g/L) as a lignin model. Most of the TA disappeared within 3.5 h, following triple-phase kinetics with two transition points: at 7 min and 60 min of ozonation for 0.4 L ozone reactor. Maximal enzymatic activity was found at the first transition point, demonstrating that very short ozonation that results in partial decomposition of TA, is enough to remediate TA's negative effect on cellulase activity. Short ozonation could decrease energy input by up to 97%, making ethanol production more economically competitive.