Bioscience Evidence 2024, Vol.14, No.5, 238-249 http://bioscipublisher.com/index.php/be 238 Feature Review Open Access The Biochemical Basis of Ethanol Fermentation and Its Industrial Applications ShudanYan Institute of Life Science, Jiyang College of Zhejiang A&F University, Zhuji, 311800, China Corresponding email: shudan.yan@jicat.org Bioscience Evidence, 2024, Vol.14, No.5 doi: 10.5376/be.2024.14.0025 Received: 01 Sep., 2024 Accepted: 08 Oct., 2024 Published: 24 Oct., 2024 Copyright © 2024 Yan, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Yan S.D., 2024, The biochemical basis of ethanol fermentation and its industrial applications, Bioscience Evidence, 14(5): 238-249 (doi: 10.5376/be.2024.14.0025) Abstract This study explored the application of ethanol fermentation in industry, especially in biofuel production and waste disposal. The study highlights several key discoveries in the field of ethanol fermentation. It was demonstrated that the aldehyde: ferredoxin oxidoreductase (AOR) enzyme is critical for ethanol formation in acetogenic bacteria, and inactivation of the bi-functional aldehyde/alcohol dehydrogenase (AdhE) significantly enhances ethanol production. Additionally, the metabolic pathways and regulatory mechanisms of ethanol-H2 co-production in anaerobic bacteria were elucidated, revealing the importance of FeFe-hydrogenases and pyruvate ferredoxin oxidoreductase (PFOR) in this process. Thermodynamic analyses identified bottlenecks in the ethanol production pathway from cellobiose in Clostridium thermocellum, suggesting potential genetic interventions to improve ethanol yield. Furthermore, metabolic engineering of Geobacillus thermoglucosidasius successfully diverted carbon flux towards ethanol production, achieving high yields under thermophilic conditions. The conservation and regulation of ethanol fermentation pathways in land plants were also examined, showing that while ethanol production is conserved, its regulation varies across plant species. The findings of this study underscore the versatility and industrial potential of ethanol fermentation. By understanding and manipulating the biochemical pathways involved, it is possible to enhance ethanol production for biofuel applications and improve waste treatment processes. These insights pave the way for future research and development in metabolic engineering and anaerobic biotechnology. Keywords Ethanol fermentation; Biofuel production; Metabolic engineering; Anaerobic biotechnology; Acetogenic bacteria; Thermophilic conditions; Regulatory mechanisms 1 Introduction Ethanol fermentation is a biochemical process in which sugars such as glucose, fructose, and sucrose are converted into cellular energy, producing ethanol and carbon dioxide as by-products. This process is primarily carried out by microorganisms like yeast and certain bacteria. Saccharomyces cerevisiae, commonly known as baker's yeast, is the most widely used organism for ethanol production due to its high efficiency in converting sugars to ethanol (Chandrakant and Bisaria, 1998; Madhavan et al., 2012; Nakanishi et al., 2017). The fermentation process can utilize various feedstocks, including lignocellulosic biomass, which is abundant and renewable, making it a promising substrate for sustainable ethanol production (Chandrakant and Bisaria, 1998; Hahn-hägerdal et al., 2007; Madhavan et al., 2012). Ethanol fermentation holds significant industrial and economic importance. It is a cornerstone of the biofuel industry, providing a renewable alternative to fossil fuels. The production of ethanol from biomass not only helps in reducing greenhouse gas emissions but also promotes energy security and rural development by utilizing agricultural residues and other waste materials (Kim et al., 2012; Nakanishi et al., 2017; Cortivo et al., 2020). Additionally, ethanol is a valuable chemical feedstock and is used in the production of various industrial chemicals, pharmaceuticals, and beverages (Bai et al., 2008; Maicas, 2021). The development of efficient fermentation technologies and engineered microbial strains has further enhanced the economic viability of ethanol production, making it a key player in the global bioeconomy (Hahn-hägerdal et al., 2007; Crespo et al., 2012; Zhang et al., 2016). This study aims to provide a comprehensive overview of the biochemical basis of ethanol fermentation and its industrial applications. The specific objectives are to discuss the key steps involved in the uptake and metabolism
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