Caproate fermentation is a metabolic process used by different bacteria to utilize different organic substrates for the production of caproic acid (hexanoic acid) as well as other valuable byproducts.[1] Caproic acid is a valuable compound in food industries as a flavor additive, feedstock for chemical industries, antimicrobial agents in the pharmaceutical industry, and more.[2] Though this process is used by varying bacterial species,[3] the most common species utilizing caproate fermentation in its metabolic process is Clostridium kluyveri.[4] This species, as well as others, utilize caproate fermentation through the breakdown of varying substrates for energy production, waste management and increased ability for survival in different environments.
Chemical structures and properties
editCaproic acid, otherwise known as hexanoic acid, can be found in two different forms. In solid form, the acid appears as a white crystalline structure, while when liquid, appears clear with a yellow tint. Any contact with caproic acid will cause irritation to various parts of the body and is toxic to humans.[5] The acid is formed through β-oxidation which elongates the short chain carboxylic acid origin using lactic acid as the electron donor to drive the process.[2] This is done through a series of reactions driven by varying enzymes. [6]
Chemical methods
editCarboxylic acids and alcohols are required as substrates for caproate fermentation. Due to the high concentrations in these substrates, they must be diluted which increases the cost and materials needed. Recently studies suggest that food waste can serve as an alternative source for these substrates, potentially reducing cost and waste.[7] The interest in creating more efficient methods for producing caproates—specifically n-caproate (hexanoate) and n-caprylate (octanoate)—has been challenged by the natural efficiency of C. kluyveri.[8] There are many different ways to produce caproate fermentation however, it is difficult to avoid disruption of the cell and effectively produce caproate. To efficiently produce caproate, optimal conditions are required including: pH, temperature, and environmental concentration.[9]
References
edit- ^ Ding, Hong-Bo; Tan, Giin-Yu Amy; Wang, Jing-Yuan (2010-12-01). "Caproate formation in mixed-culture fermentative hydrogen production". Bioresource Technology. 101 (24): 9550–9559. Bibcode:2010BiTec.101.9550D. doi:10.1016/j.biortech.2010.07.056. ISSN 0960-8524.
- ^ a b Cavalcante, Willame de Araújo; Leitão, Renato Carrhá; Gehring, Tito A.; Angenent, Largus T.; Santaella, Sandra Tédde (2017-03-01). "Anaerobic fermentation for n-caproic acid production: A review". Process Biochemistry. 54: 106–119. doi:10.1016/j.procbio.2016.12.024. ISSN 1359-5113.
- ^ Hung, Chun-Hsiung; Chang, Yi-Tang; Chang, Yu-Jie (September 2011). "Roles of microorganisms other than Clostridium and Enterobacter in anaerobic fermentative biohydrogen production systems--a review". Bioresource Technology. 102 (18): 8437–8444. doi:10.1016/j.biortech.2011.02.084. ISSN 1873-2976. PMID 21429742.
- ^ Yin, Yanan; Zhang, Yifeng; Karakashev, Dimitar Borisov; Wang, Jianlong; Angelidaki, Irini (October 2017). "Biological caproate production by Clostridium kluyveri from ethanol and acetate as carbon sources". Bioresource Technology. 241: 638–644. Bibcode:2017BiTec.241..638Y. doi:10.1016/j.biortech.2017.05.184. ISSN 1873-2976. PMID 28605728.
- ^ PubChem. "Caproic Acid". pubchem.ncbi.nlm.nih.gov. Retrieved 2024-10-16.
- ^ Dong, Wenjian; Yang, Youli; Liu, Chao; Zhang, Jiachao; Pan, Junting; Luo, Lin; Wu, Genyi; Awasthi, Mukesh Kumar; Yan, Binghua (2023-04-01). "Caproic acid production from anaerobic fermentation of organic waste - Pathways and microbial perspective". Renewable and Sustainable Energy Reviews. 175: 113181. Bibcode:2023RSERv.17513181D. doi:10.1016/j.rser.2023.113181. ISSN 1364-0321.
- ^ Zhang, Cunsheng; Liang, Tianyu; Li, Chengmei; Ji, Hairui; Liu, Hongze; Ling, Zhihui; Tian, Zhongjian (2024-09-06). "Caproate production from the mixture of corn straw and food waste via chain elongation with reinforcement of biofilm". Process Biochemistry. 147: 137–146. doi:10.1016/j.procbio.2024.08.019.
- ^ Fernández-Blanco, Carla; Pereira, Alexandra; Veiga, María C.; Kennes, Christian; Ganigué, Ramon (September 2024). "Comprehensive comparative study on n-caproate production by Clostridium kluyveri: batch vs. continuous operation modes". Bioresource Technology. 408: 131138. Bibcode:2024BiTec.40831138F. doi:10.1016/j.biortech.2024.131138. PMID 39043275.
- ^ Yu, Jiangnan; Liao, Jialin; Huang, Zhenxing; Wu, Peng; Zhao, Mingxing; Liu, Chunmei; Ruan, Wenquan (2019-07-01). "Enhanced Anaerobic Mixed Culture Fermentation with Anion-Exchange Resin for Caproate Production". Processes. 7 (7): 404. doi:10.3390/pr7070404. ISSN 2227-9717.