# Acidogenesis > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Acidogenesis > Markdown URL: https://mediated.wiki/source/Acidogenesis.md > Source: https://en.wikipedia.org/wiki/Acidogenesis > Source revision: 1255103741 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) {{short description|Second of four stages of anaerobic digestion}} '''Acidogenesis''' is the second stage in the four stages of [anaerobic digestion](/source/anaerobic_digestion): * [Hydrolysis](/source/Hydrolysis): A chemical reaction where [particulate](/source/particulate)s are solubilized and large [polymer](/source/polymer)s converted into simpler [monomer](/source/monomer)s; * Acidogenesis: A biological reaction where simple monomers are converted into volatile [fatty acid](/source/fatty_acid)s; * [Acetogenesis](/source/Acetogenesis): A biological reaction where volatile fatty acids are converted into [acetic acid](/source/acetic_acid), [carbon dioxide](/source/carbon_dioxide), and [hydrogen](/source/hydrogen) * [Methanogenesis](/source/Methanogenesis): A biological reaction where [acetate](/source/acetate)s are converted into [methane](/source/methane) and carbon dioxide, while hydrogen is consumed. Anaerobic digestion is a complex [biochemical](/source/Biochemistry) process of [biologically](/source/Biology) mediated reactions by a consortium of [microorganism](/source/microorganism)s to convert [organic compound](/source/organic_compound)s into methane and carbon dioxide. It is a stabilization process that reduces odor, [pathogen](/source/pathogen)s, and waste volume. [Hydrolytic](/source/Hydrolysis) [bacteria](/source/bacteria) form a variety of [reduced](/source/Redox) end-products from the [fermentation](/source/Fermentation_(biochemistry)) of a given [substrate](/source/Substrate_(biology)). One fundamental question that arises concerns the [metabolic](/source/Metabolism) features that control [carbon](/source/carbon) and [electron](/source/electron) flow to a given reduced end-product during [pure culture](/source/pure_culture) and mixed [methanogenic](/source/Methanogenesis) [cultures](/source/Microbiological_culture) of hydrolytic bacteria. ''[Thermoanaerobium brockii](/source/Thermoanaerobium_brockii)'' is a representative [thermophilic](/source/Thermophile), hydrolytic bacterium, which ferments [glucose](/source/glucose), via the [Embden–Meyerhof Parnas Pathway](/source/Embden%E2%80%93Meyerhof_pathway). ''T. brockii'' is an atypical hetero-[lactic acid](/source/lactic_acid) bacterium because it forms molecular hydrogen ([H2](/source/Dihydrogen)), in addition to lactic acid and [ethanol](/source/ethanol). The reduced end-products of glucose fermentation are [enzymatically](/source/Enzyme) formed from [pyruvate](/source/pyruvate), via the following mechanisms: lactate by [fructose 1-6](/source/Fructose_1%2C6-bisphosphatase) all-[phosphate](/source/phosphate) ([F6P](/source/Fructose_6-phosphate)) activated [lactate dehydrogenase](/source/lactate_dehydrogenase); H2 by pyruvate [ferredoxin](/source/ferredoxin) [oxidoreductase](/source/oxidoreductase) and [hydrogenase](/source/hydrogenase); and ethanol via [NADH](/source/NADH)- and [NADPH](/source/NADPH)-linked [alcohol dehydrogenase](/source/alcohol_dehydrogenase).Marchaim, U. (1992). FAO Agricultural Services Bulletin – 95: [Biogas](/source/Biogas) process for sustainable development, FAO – [http://www.fao.org Food and Agriculture Organization] of the United Nations, ISSN 1010-1365 (1/9/2003). By its side, the acidogenic activity was found in the early 20th century, but it was not until the mid-1960s that the engineering of phases separation was assumed in order to improve the stability and [waste digesters treatment](/source/Waste_treatment).Alexiou, I.E. and Panter, K. (2004). A review of two phase applications to define best practice for the treatment of various waste streams. Anaerobic Digestion 10th World Congress, September 2004. Montreal, Quebec, Canada. In this phase, complex [molecule](/source/molecule)s ([carbohydrate](/source/carbohydrate)s, [lipid](/source/lipid)s, and [protein](/source/protein)s) are [depolymerized](/source/depolymerization) into soluble compounds by hydrolytic enzymes ([cellulase](/source/cellulase)s, [hemicellulase](/source/hemicellulase)s, [amylase](/source/amylase)s, [lipase](/source/lipase)s and [protease](/source/protease)s). The hydrolyzed compounds are fermented into volatile fatty acids (acetate, [propionate](/source/propionate), [butyrate](/source/butyrate), and [lactate](/source/lactic_acid)), neutral compounds (ethanol, [methanol](/source/methanol)), [ammonia](/source/ammonia), hydrogen and carbon dioxide.{{in lang|es}} Cairó, J.J. and París, J.M. (1988). Microbiología de la digestión anaerobia, metanogénesis. 4o Seminario de Depuración Anaerobia de Aguas Residuales. Valladolid. F.F. Polanco, P.A. García y S. Hernándo. (Eds.) pp. 41–51.Dinopolou, G., Rudd, T. and Lester, J.N. (1987). Anaerobic acidogenesis of a complex wastewater: I. The influence of operational parameters on reactor performance. Biotech. And Bioeng. 31: 958 – 968.{{in lang|fr}} Laroche, M. (1983). Metabolisme intermediaire des acides gras volatils en fermentation methanique. These de Docteur – Ingenieur en Sciences Alimentaires_Fermentations. Institut National de la Recherche Agronomique, France. [Acetogenesis](/source/Acetogenesis) is one of the main reactions of this stage, in this, the intermediary [metabolite](/source/metabolite)s produced are metabolized to acetate, hydrogen and carbonic gas by the three main groups of bacteria: * [homoacetogen](/source/homoacetogen)s; * [syntrophe](/source/syntrophe)s; and * [sulphoreductor](/source/sulphoreductor)s. For the [acetic acid](/source/acetic_acid) production are considered three kind of bacteria: * ''[Clostridium aceticum](/source/Clostridium_aceticum)''; * ''[Acetobacter woodii](/source/Acetobacter_woodii)''; and * ''[Clostridium termoautotrophicum](/source/Clostridium_termoautotrophicum)''. Winter y Wolfe, in 1979, demonstrated that ''A. woodii'' in syntrophic association with ''[Methanosarcina](/source/Methanosarcina)'' produce methane and carbon dioxide from [fructose](/source/fructose), instead of three molecules of acetate.Winter, J.U. and Wolfe, R.S. (1979). Complete degradation of carbohydrates to CO2 and methane by syntrophic cultures of Acetobacterium woodii y Methanosarcina barkeri. Arch. Microbiol. 121: 97 – 102. ''[Moorella thermoacetica](/source/Moorella_thermoacetica)'' and ''[Clostridium formiaceticum](/source/Clostridium_formiaceticum)'' are able to reduce the carbonic gas to acetate, but they do not have [hydrogenase](/source/hydrogenase)s which inhabilite the hydrogen use, so they can produce three molecules of acetate from fructose. Acetic acid is equally a co-[metabolite](/source/metabolite) of the organic substrates fermentation ([sugars](/source/sugars), [glycerol](/source/glycerol), [lactic acid](/source/lactic_acid), etc.) by diverse groups of microorganisms which produce different acids: *[Propionic](/source/Propionate) bacteria ([propionate](/source/propionate) + acetate); * ''[Clostridium](/source/Clostridium)'' (butyrate + acetate); * [Enterobacteria](/source/Enterobacteria) (acetate + lactate); and * Hetero-fermentative bacteria (acetate, propionate, butyrate, [valerate](/source/Valeric_acid), etc.). ==References== {{Reflist}} Category:Anaerobic digestion Category:Bacteriology Category:Biochemical reactions --- Adapted from the Wikipedia article [Acidogenesis](https://en.wikipedia.org/wiki/Acidogenesis) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Acidogenesis?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.