Detoxification of Dilute-Acid and Ionic-Liquid Pretreated Wheat Straw Hydrolysates to Improve Succinic Acid Fermentation

Biomass hydrolysate may be used for the production of succinic acid via fermentation. However, concentrated hydrolysate produced from dilute acid or ionic liquid pretreatment contain several inhibitors, especially low molecule weight phenolic compounds (LMWPCs) that strongly inhibit the growth of A. succinogenes. In this study, we evaluated solid phase adsorption (activated charcoal, ion-exchange resin, and polymeric resin) and a novel liquid-liquid extraction (LLE) process for detoxifying wheat straw hydrolysate. The results showed that although solid phase adsorption removed the major inhibitors, a 3%-16% sugar loss reduced the overall succinic acid yield (62% to 69%, g-succinic acid/g-sugar). The LLE process using tri-n-octylphosphine oxide (TOPO) or tri-n-octylamine (TOA) efficiently removed nearly 100% of LMWPCs and more than 60% of the total phenolics from both hydrolysates with no sugar loss. Succinic acid fermentation yield on the LLE-detoxified hydrolysates was nearly 75% (g-succinic acid/g-sugar), which was as good as the yield from the model sugar control.