Characterization of the impact of high solids deacetylation of corn stover in a cellulosic ethanol process

In recent years, lignocellulosic pretreatment processes have evolved to be capable of producing increasingly highly digestible substrates that when coupled with advanced enzymes have enabled the production of hydrolyzates with sugar concentrations of greater than 150 grams per liter. However, these higher solids slurries and more-concentrated solutions, while potentially improving the economics of bio-based fuels and chemicals, also contain high concentrations of potent fermentation inhibitors such as acetic acid. A process, called deacetylation, has been developed that, when implemented prior to pretreatment, removes a significant portion of acetyl groups from the hemicellulose structure of corn stover. Traditionally, this process is executed at low solids with an excess of catalyst (sodium hydroxide) and solubilizes 80% of acetyl groups and 5% of xylan present in the original corn stover. Recent work indicates that the process could be done at higher solids loadings with reduced catalyst usage and still remove 70% of acetyl groups while also reducing xylan loss. Results characterizing the revised, high-solids deacetylation process, as well as the impact on downstream operations including pretreatment, enzymatic hydrolysis and fermentation will be presented.