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

Area of Science:

• Microbiology
• Biotechnology
• Chemical Engineering

Background:

• Growing industrial demand for medium-chain carboxylic acids (MCCAs) such as n-caproate and n-caprylate.
• Chain elongation process as a key method for MCCA production.
• Clostridium kluyveri as a promising microorganism for MCCA synthesis.

Purpose of the Study:

• To comprehensively assess the behavior and MCCA production of Clostridium kluyveri.
• To compare MCCA production in batch and continuous modes.
• To investigate the impact of different ethanol:acetate molar ratios on MCCA yield and selectivity.

Main Methods:

• Cultivation of Clostridium kluyveri in batch and continuous modes.
• Varying ethanol:acetate molar ratios (1.5:1, 3.5:1, and 5.5:1).
• Quantification of MCCA concentrations and selectivity.

Main Results:

• Highest n-caproate concentration (12.9 g/L) and selectivity (92.9%) achieved in batch mode at a 3.5:1 ratio.
• Batch mode showed higher selectivity than continuous mode at ethanol:acetate ratios of 3.5:1 and 5.5:1.
• Continuous operation at a 3.5:1 ratio yielded the highest steady-state n-caproate (9.5 g/L) and n-caprylate (0.35 g/L).
• Increased ethanol:acetate ratios led to higher excessive ethanol oxidation, potentially limiting production.

Conclusions:

• Clostridium kluyveri is efficient in producing MCCAs in both batch and continuous modes.
• A 3.5:1 ethanol:acetate ratio is optimal for maximizing n-caproate production and selectivity.
• Operational mode and substrate ratio significantly influence MCCA production efficiency.