Performance and stability of Amberlite™ IRA-67 ion exchange resin for product extraction and pH control during homolactic fermentation of corn stover sugars

A thermotolerant, mixed culture with Bacillus coagulans as a dominating bacterium was grown for production of lactic acid. Acid extraction using Amberlite (TM) IRA-67 weak base resin in a recirculation loop with a fermentation vessel was implemented to maximize culture productivity by maintaining a concentration of lactic acid below 20 g/L. Productivity of this fermentation was found to be 1.3-fold higher than a control fed-batch process. Characterization of the resin through isotherm analysis produced data that fit well (R-2 > 0.99) to both Langmuir and Redlich-Petersen models with a Langmuir monolayer loading of 203.8 mg acid/g resin. Resin stability was tested over 108 days of fermentation on corn stover hydrolysate. During this fermentation, resin capacities for lactic and acetic acid were on average 112.2 mg/g and 19.6 mg/g, respectively, with no statistical evidence for change lactic acid capacity after reuse. However, acetic acid capacity on average dropped 4.9% per reuse. (C) 2014 Published by Elsevier B.V.