Caproic acid production from acid whey via open culture fermentation – Evaluation of the role of electron donors and downstream processing

• Published in: Bioresource technology 2019-05, Vol.279, p.74-83
• Main Authors: Chwialkowska, Joanna, Duber, Anna, Zagrodnik, Roman, Walkiewicz, Filip, Łężyk, Mateusz, Oleskowicz-Popiel, Piotr
• Format: Article
• Language: English
• Subjects: Anaerobic open culture fermentation; Chain elongation; Ionic liquids; Liquid-liquid extraction; Techno-economic analysis
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2019.01.086

[Display omitted] •Increase in carboxylates concentration was accompanied by a decline in lactate.•Lactate with ethanol promote lactate oxidation coupled to chain elongation.•Lactic acid strongly affects the chain elongation.•Ionic liquid are promising for liquid-liquid extraction of carboxylates.•It is possible to economically effective produce caproic acid. The objective of this study was to investigate the potential of supplementing ethanol and lactic acid as electron donors in reverse β-oxidation for short chain carboxylic acids chain elongation during anaerobic fermentation of acid whey. Best results were achieved when lactic acid was added at concentration of 300 mM. It resulted in medium chain carboxylic acids (MCCAs) concentration of 5.0 g/L. In the trials with ethanol addition, the overall yield was 20% lower. Subsequently liquid-liquid extraction with ionic liquids (ILs) was investigated as a potential purification method of caproic acid. The most promising, with respect to recovery of caproic acid, was piperazinium IL [C1C1C10Ppz][NTF2], however, the selectivity was only 0.39. Less effective [C1C1C6Ppz][NTF2] recovered 85.9% of caproic acid while reaching a higher selectivity of 0.53. Technoeconomic model revealed that to meet the conservative value of $2.25 per kg of caproic acid, the downstream processing should not exceed $0.65 per kg.