Selective carboxylate production by controlling hydrogen, carbon dioxide and substrate concentrations in mixed culture fermentation

Abstract

This research demonstrated the selective production of n-butyrate from mixed culture by applying 2bar carbon dioxide into the headspace of batch fermenters or by increasing the initial substrate concentration. The effect of increasing initial substrate concentration was investigated at 8, 13.5 and 23gCOD/L with potato processing waste stream. Within 1week of incubation, n-butyrate fraction selectively increased up to 83% by applying 2bar hydrogen or 78% by applying carbon dioxide into the headspace whereas it was only 59% in the control reactor. Although the fraction of n-butyrate was elevated, the concentration remained lower than in the control. Both the highest concentration and fraction of n-butyrate were observed under the highest initial substrate concentration without headspace addition. The concentration was 10gCOD/L with 73% fraction. The operational conditions obtained from batch experiments for selective n-butyrate production were validated in a continuous process.