Removal of Acetic Acid from Spent Sulfite Liquor Using Anion Exchange Resin for Effective Xylose Fermentation with Pichia stipitis

Acetic acid is one of the major inhibitors of spent sulfite liquor (SSL) fermentation for ethanol production. The objective of this study was to remove acetic acid from hardwood SSL using anion exchange resin in order to achieve effective fermentation with Pichia stipitis CBS6054. Lignosulfonate, as well as sulfate and sulfite ions in the SSL hindered the removal of acetic acid by anion exchange resins. CaO treatment was an effective method for removing these materials from SSL, which facilitated the removal of acetic acid in the subsequent ion exchange resin treatment. A two-stage strong base ion exchange resin (OH form) treatment removed approximately 90% of the acetic acid from CaOtreated SSL, which decreased the acetic acid concentration to less than 1 g/L. The combined treatment of CaO and ion exchange resin treatments in a relatively short time achieved the selective removal of acetic acid from SSL and significantly increased the ethanol production from SSL.