Succinic acid production from rice husk hemicellulosic liquor: evaluation of fermentation inhibitors

Abstract

Lignocellulosic hydrolysates typically contain inhibitors that limit microbial fermentation. Based on the characterization of rice husk autohydrolysis liquor, this study assessed the individual and combined effects of the main inhibitors identified—acetic acid, formic acid and furfural—on succinic acid fermentation. Batch experiments were performed using a defined synthetic medium containing glucose and xylose as the carbon sources. A control fermentation (without inhibitors addition) was compared against media supplemented with each inhibitor separately and with the three inhibitors simultaneously, at concentrations representative of those found in the liquor. In addition, a fermentation using rice husk autohydrolysis liquor as the carbon source was performed. Results showed that acetic acid (~3.0–3.3 g/L) suppressed succinic acid fermentation in synthetic medium. However, when the hemicellulosic hydrolysate was evaluated, A. succinogenes DSM 22257 was capable of fermenting after a detoxification step resulting in ~8–9 g/L succinic acid.