Detoxification of hemicellulose-rich poplar hydrolysate by polymeric resins for improved ethanol fermentability

- ASL removed effectively by both IRA-400 (OH−) and XAD-4.
- Xylo-saccharides loss significantly reduced with IRA-400 (OH−) treatment.
- Significant phenolics and HMF removal, poor acetic acid removal by IRA-400 (OH−).
- Better fermentability with IRA-400 (OH−) treatment prior to enzymatic hydrolysis.

Inhibitors generated during biomass pretreatment negatively affect fermentability of biomass hydrolysates and need to be removed prior to fermentation. In this study, four different polymeric resins were evaluated for their abilities to remove acid soluble lignin (ASL) from poplar hydrolysate. The ASL removal capabilities of Amberlite IRA-400 (OH−) and XAD-4 were similar (96.7% and 97.3%, respectively), however 88% of xylo-saccharides (XS) were lost with XAD-4 treatment as compared to 21% with IRA-400 (OH−) treatment. IRA-400 (OH−) was also efficient in adsorption of aromatic-based inhibitors such as benzoic acid, vanillin and 4-hydroxybenzoic acid. The consecutive resin IRA-400 (OH−) → enzyme (HTec2) treatment removed 79.5% of ASL from the hydrolysate at a loss of only 9.5% of xylo-based carbohydrates (XBC). This improved the hydrolysate fermentability to ethanol attaining 41.5 g/L ethanol titer and 89.6% ethanol yield at a sugar utilization efficiency of 95.3% after 72 h of fermentation.