Comprehensive comparative study on n-caproate production by Clostridium kluyveri: batch vs. continuous operation modes

• Published in: Bioresource technology 2024-09, Vol.408, p.131138, Article 131138
• Main Authors: Fernández-Blanco, Carla, Pereira, Alexandra, Veiga, María C., Kennes, Christian, Ganigué, Ramon
• Format: Article
• Language: English
• Subjects: Batch fermentation; Chain elongation; Clostridium kluyveri; Continuous fermentation; n-caproate; n-caprylate
• ISSN: 0960-8524; 1873-2976; 1873-2976
• DOI: 10.1016/j.biortech.2024.131138

[Display omitted] •C. kluyveri thrived in batch & continuous systems with three ethanol:acetate ratios.•12.9 g/L (92.9 % selectivity) caproate were reached in batch mode with a 3.5:1 ratio.•Higher ratios favored batch mode selectivity over continuous mode at ratios ≥ 3.5:1.•Pure-strain continuous bioreactor worked without contamination for over 23 days.•An increase in EEO was observed as the ethanol:acetate molar ratio increased. Recently, there has been notable interest in researching and industrially producing medium-chain carboxylic acids (MCCAs) like n-caproate and n-caprylate via chain elongation process. This study presents a comprehensive assessment of the behavior and MCCA production profiles of Clostridium kluyveri in batch and continuous modes, at different ethanol:acetate molar ratios (1.5:1, 3.5:1 and 5.5:1). The highest n-caproate concentration, 12.9 ± 0.67 g/L (92.9 ± 1.39 % MCCA selectivity), was achieved in batch mode at a 3.5:1 ratio. Interestingly, higher ratios favored batch mode selectivity over continuous mode when this was equal or higher to 3.5:1. Steady state operation yielded the highest n-caproate (9.5 ± 0.13 g/L) and n-caprylate (0.35 ± 0.020 g/L) concentrations at the 3.5:1 ratio. Increased ethanol:acetate ratios led to a higher excessive ethanol oxidation (EEO) in both operational modes, potentially limiting n-caproate production and selectivity, especially at the 5.5:1 ratio. Overall, this study reports the efficient MCCA production of both batch and continuous modes by C. kluyveri.