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Electro-Fermentation Technology: Synthesis of Chemicals and Biofuels
Published in Kuppam Chandrasekhar, Satya Eswari Jujjavarapu, Bio-Electrochemical Systems, 2022
Devashish Tribhuvan, V. Vinay, Saurav Gite, Shadab Ahmed
Methane is an important molecule that is primarily used as biofuel to make heat and electricity, and it is also a precursor of various chemicals. Methane is economical and has diverse applications in industries. Methane could be considered a powerhouse of energy (Hwang et al., 2018). Methanogenesis is the process by which methanogens produce methane by reducing carbon dioxide. Organic molecules like formate, acetate, and methylamine are used with CO2 and H2 as substrates for methane production. Even though the substrates are very simple, methane formation is a complex biochemical process that involves various coenzymes and genes. Methanogens are categorized into three groups according to the substrate used: acetolactic methanogens, hydrogenotrophic methanogens, and methylotrophic methanogens (Table 6.2) (Fu et al., 2021).
Metabolic Engineering of Methanogenic Archaea for Biomethane Production from Renewable Biomass
Published in Sonil Nanda, Prakash K. Sarangi, Biomethane, 2022
Rajesh Kanna Gopal, Preethy P. Raj, Ajinath Dukare, Roshan Kumar
In recent decades, the anaerobic archaea have been studied and implemented in industrial processes for wastewater and sewage treatment. However, microbiota involved in this process is more complex even within the same genus based on the substrate used. Hence, extensive research on the methanogenic community of pure and consortia of microbes are to be carried out to enhance biomethane production. Therefore, for the efficient biomethane production process, clear studies on the microorganisms and its functions are more essential to completely use organic waste. Recent advancements in the genetic implementation of methanogens are proven feasible for methanogenesis; hence, they are not economically feasible due to strict anaerobic conditions and slow growth. However, advanced genetic engineering tools are the most reasonable way to synthesize value-added products from potential methanogens.
Extremophilic Microbes and their Extremozymes for Industry and Allied Sectors
Published in Ajar Nath Yadav, Ali Asghar Rastegari, Neelam Yadav, Microbiomes of Extreme Environments, 2021
Hiran Kanti Santra, Debdulal Banerjee
Methanogenic archaea represents the source for clean and low-cost energy generation (Reeve et al. 1997). Another example in molecular biology includes the use of Taq DNA polymerase from Thermus aquaticus, which is randomly used in Polymerase Chain Reactions (PCRs) (Canganella and Wiegel 2011). Agarases that are capable of hydrolyzing agar have a large application at the laboratory and industrial level for liberating DNA and other bio-molecules stuck in agarose. They are also effective tools for the bioremediation of agar used daily for laboratory purposes and extraction of bioactive or medicinal compounds from algae and seaweed. Bacteriostatic neoagarosaccharides are also the product of agarase activity. They slow down the process of starch degradation, promote anticancer activity and have antioxidative potentials (Giordano et al. 2006; Elleuche et al. 2014). A very authentic source of agarase is the salt-tolerant extremophile Pseudoalteromonads, Pseudomonas, and Vibrio (DasSarma et al. 2010). Methanogens are not as widely characterized compared to other extremophiles. But methanogens are used in some processes such as, biogas production or organic waste decomposition by anaerobic fermentation (Zhang et al. 2011; Zhu et al. 2011).
Commercial formulation amendment transiently affects the microbial composition but not the biogas production of a full scale methanogenic UASB reactor
Published in Environmental Technology, 2020
A. Cabezas, P. Bovio, C. Etchebehere
In anaerobic environments, the organic material is degraded in a cascade process where complex biopolymers are first hydrolyzed and degraded by fermentative microorganisms that produce hydrogen, carbon dioxide and volatile fatty acids (butyrate, propionate, acetate and formate) as products. Methanogens use H2/CO2 and/or acetate as the main substrates for methane production. Higher organic compounds such as propionate and butyrate, that are typical intermediates in methanogenic environments, are not degraded by methanogens. Therefore, acetogenic bacteria are required to degrade such compounds to the methanogenic substrates [4]. These bacteria grow only in obligate syntrophy with methanogens due to thermodynamic constrains. For lipid rich wastewater, like dairy effluent, a hydrolytic step converts lipids in glycerol and long chain fatty acids (LCFA) which are then further degraded anaerobically via the ß-oxidation pathway by syntrophic bacteria to acetate and H2, the substrates for methanogenesis. Only a few bacteria, all belonging to the Syntrophomonadaceae family, have been described as LCFA-degrading bacteria (reviewed in [10]). Hydrolysis of lipids is generally regarded as a fast process, and the rate-limiting step is the degradation of LCFAs [4,10].
Waste into energy conversion technologies and conversion of food wastes into the potential products: a review
Published in International Journal of Ambient Energy, 2021
Jeya Jeevahan, A. Anderson, V. Sriram, R. B. Durairaj, G. Britto Joseph, G. Mageshwaran
Biogas can be produced from anaerobic digestion. It contains, mainly, of 65% methane and 35% carbon dioxide with a trace amount of hydrogen sulphide and water vapour. It is lighter than air, i.e. about 20% lighter than air. It cannot be converted to liquid state under normal temperature, as opposed to liquefied petroleum gas(LPG). After removing CO2, bio-methane (enriched biogas) can be compressed into cylinders for easy transportation. Moreover, CNG technology can be used for the enriched biogas which has the potential of biogas usage in all applications where CNG is currently used (Leung and Wang 2016). When biogas is used as fuel, CO2 is removed from the gas so that the energy content of the biogas is increased and can be stored at high pressure (McKay 2002). An interesting fact is that both biogas and natural gas are produced in anaerobic conditions and methane is the major component. However, it takes million years to produce natural gas from dead biomass, whereas it takes only about 15–20 days to produce biogas from organic wastes. Methanogens (methane-forming bacteria) are responsible for converting the components of acidogenesis and acetogenesis stages of anaerobic digestion into methane and carbon dioxide. That is, acidogenesis produces VFAs, alcohol, ketones, CO2, H2, NH3, H2S, etc. and acetogenesis further breaks down alcohols and short-chain volatile acids to acetic acid and hydrogen. Finally, methanogens convert all these components into methane and carbon dioxide (Zhang et al. 2007). Some of the works done on the conversion of food waste into biogas are presented in the Table 3.
Production of biofuels from fish wastes: an overview
Published in Biofuels, 2019
D. Yuvaraj, B. Bharathiraja, J. Rithika, S. Dhanasree, V. Ezhilarasi, A. Lavanya, R. Praveenkumar
Anaerobic digestion is a collection of processes by which micro-organisms breakdown biodegradable materials in the absence of air. Some micro-organism has been used for this process like Acetogensand Methanogens which convert the organic acid into methane. The final products from anaerobic digestion are digestate including a variety of nutrients, and biogas containing CH4 (50–75%), CO2 (25–45%) and by-products such as H2S (<1%) (Table 1) [33]. The decomposition process comprises four steps as follows: