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

•Bacillus culture used for non-sterile lactic acid fermentation of biomass sugars.•Extractive fermentation of lactic acid with ion exchange resin was conducted.•1.33-Fold increase in productivity observed over traditional fed batch fermentation.•Fermentation pH was controlled using ion exchange resin to extract product.•Resin capacity for acid was stable over 100 days of fermentation on corn stover.

A thermotolerant, mixed culture with Bacillus coagulans as a dominating bacterium was grown for production of lactic acid. Acid extraction using Amberlite™ 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 (R2 > 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.