4-03: Removal and recovery of enzymatic and fermentation inhibitory compounds from biomass slurries for enhanced biorefinery process efficiencies

Within the biochemical production route of the biorefinery paradigm, pretreatment of the lignocellulosic feedstock inevitably produces a complex slurry containing insoluble solids along with soluble compounds such as sugars, furans, acids, and phenolics.  Many of the non-monomeric sugar compounds have been shown to be inhibitory to enzymes and microbial organisms that are used for downstream hydrolysis and fermentation, regardless of the eventual product being targeted (e.g., ethanol, butanol, or other advanced biofuels and biochemicals).  Here, two novel separation technologies, polyelectrolyte polymer adsorption (for removal of insoluble lignin along with furans and phenolics) and resin-wafer electrodeionization (RW-EDI, for removal of mineral and organic acids), have been evaluated to clarify and detoxify a dilute acid pretreated biomass slurry.  Following inhibitory compound removal, with either the polyelectrolyte or RW-EDI as individual operations or in combination, enzymatic hydrolysis and fermentation were completed.  Under optimal separation conditions we have shown that the rate of enzymatic hydrolysis can be improved by approximately 40% with 20% higher glucose yield.  Furthermore, downstream batch fermentation to ethanol using Saccharomyces cerevisiae can be completed 65% faster with a 20% higher final ethanol concentration.  In addition to different separation schemes, the effects of enzyme dosing, solids washing, and the ability to recover purified inhibitory compounds were all evaluated.