Bioscience Evidence 2024, Vol.14, No.2, 81-92 http://bioscipublisher.com/index.php/be 81 Review and Progress Open Access Metabolic Pathways and Genetic Engineering of Anaerobic Bacteria for Biohydrogen Production Kaiwen Liang Biomass Research Center, Hainan Institute of Tropical Agricultural Resouces, Sanya, 572025, Hainan, China Corresponding author email: kaiwen.liang@hitar.org Bioscience Evidence, 2024, Vol.14, No.2 doi: 10.5376/be.2024.14.0010 Received: 03 Mar., 2024 Accepted: 08 Apr., 2024 Published: 21 Apr., 2024 Copyright © 2024 Liang, 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: Liang K.W., 2024, Metabolic pathways and genetic engineering of anaerobic bacteria for biohydrogen production, Bioscience Evidence, 14(2): 81-92 (doi: 10.5376/be.2024.14.0010) Abstract Biohydrogen production, as a promising direction for sustainable energy production, leverages the metabolic capabilities of anaerobic bacteria. This study provides a comprehensive review of the metabolic pathways involved in biohydrogen production, with a focus on acidogenic fermentation and butyrate-type fermentation, as well as the critical role of hydrogenases in these processes. The research highlights the latest advancements in genetic engineering technologies, including CRISPR-Cas9, gene knockout, and synthetic biology approaches, which have played significant roles in optimizing metabolic pathways and increasing hydrogen yield. Key developments include the successful modification of anaerobic bacteria such as Clostridium acetobutylicumand Thermotoga maritima, leading to substantial increases in hydrogen production, and the integration of omics technologies to identify new pathway optimization targets. The study also explores the potential of co-culture systems and microbial communities in enhancing biohydrogen production and discusses challenges related to economic scalability, biosafety, and environmental impact. This research offers new perspectives on the fundamental scientific principles of bioenergy conversion, promoting innovation and development in biotechnology for clean energy. Keywords Biohydrogen production; Anaerobic bacteria; Metabolic pathways; Genetic engineering; CRISPR-Cas9; Hydrogenases; Synthetic biology 1 Introduction The rising demand for sustainable and renewable energy sources has intensified research efforts into alternative energy technologies. Among these, biohydrogen production has emerged as a promising candidate, offering a clean, efficient, and environmentally friendly energy carrier. Biohydrogen, produced through biological processes, is particularly attractive due to its potential for large-scale production using diverse biomass feedstocks. This process not only provides a renewable energy source but also contributes to the reduction of greenhouse gas emissions, making it an integral part of future energy solutions (Saravanan et al., 2021; Lin, 2024). Biohydrogen production leverages the natural metabolic processes of microorganisms to convert organic substrates into hydrogen gas. This biological approach is advantageous over traditional methods, such as steam reforming of hydrocarbons, as it operates under milder conditions, has lower energy requirements, and can utilize a wide range of renewable organic materials (Aslam et al., 2018). Various microorganisms, including algae, cyanobacteria, and anaerobic bacteria, have been studied for their hydrogen-producing capabilities. Among these, anaerobic bacteria are particularly notable for their efficiency in converting complex organic compounds into hydrogen under oxygen-free conditions (Fuess et al., 2019). Anaerobic bacteria play a critical role in biohydrogen production due to their ability to thrive in oxygen-depleted environments and efficiently degrade organic matter (Bengelsdorf et al., 2018). These bacteria, through fermentation and anaerobic digestion processes, are capable of producing significant amounts of hydrogen. Their metabolic pathways are diverse and can be optimized for enhanced hydrogen yield through genetic engineering (El-Dalatony et al., 2020). The study of these bacteria not only aids in understanding the fundamental mechanisms of biohydrogen production but also provides opportunities to engineer strains with improved hydrogen production capacities, paving the way for industrial-scale applications (Jia et al., 2021).
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