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Biological Process for Butanol Production
Published in Jay J. Cheng, Biomass to Renewable Energy Processes, 2017
Maurycy Daroch, Jian-Hang Zhu, Fangxiao Yang
Acidogenesis starts in two major branch points of the metabolism acetyl-CoA and butyryl-CoA. During the acid-producing phase, acetate and butyrate are produced from acetyl-CoA and butyryl-CoA with two analogous, yet distinct sets of enzymes. Formation of acetate from acetyl-CoA is a two-step reaction catalyzed by phosphate acetyltransferase (phosphotransacetylase) and acetate kinase. The first of the two reactions yields acetyl phosphate from acetyl-CoA; the second one dephosphorylates acetyl phosphate to acetate yielding ATP as the second product. Analogously, formation of butyrate from butyrate-CoA follows the same pattern catalyzed by phosphate butyryltransferase (phosphotransbutyrylase) and butyryl kinase. Reaction catalyzed by phosphate butyryltransferase yields butyryl phosphate, while subsequent dephosphorylation reaction yields butyrate and ATP. Although in principle C. acetobutylicum can also convert pyruvate to lactate under certain conditions, this reaction is not considered an acidogenic reaction as this pathway is not operational under normal conditions (Jones and Woods, 1986). The two main sets of reactions originating from acetyl- and butyryl-CoA are important sources of ATP for the metabolism, but yield in the formation of highly acidic byproducts (acetate, butyrate) that in high concentrations of fermentation become toxic to the cells and induce metabolic shift from acidogenesis to solvengenesis.
Removal of nonylphenol ethoxylate surfactant in batch reactors: emphasis on methanogenic potential and microbial community characterization under optimized conditions
Published in Environmental Technology, 2022
Rômulo Mota Teixeira, Isabel Kimiko Sakamoto, Fabrício Motteran, Franciele Pereira Camargo, Maria Bernadete Amâncio Varesche
Other KOs related to enzymes involved in methanogenesis observed in smaller proportions in both samples were phosphate acetyltransferase (K13788), heterodisulfide reductase (K03388 and K03389), methenyltetrahydromethanopterin cyclohydrolase (K01499) and acetate kinase (K00925). The acetate kinase enzyme is closely related to the production of methane from acetic acid, and is commonly related to Methanosaeta, observed in a relative abundance of 30.28 and 32.63% in the optimized and control conditions, respectively.