Acidogenesis

 ( Anaerobic Digestion ) 

Acidogenesis is the second stage in the four stages of anaerobic digestion:

• Hydrolysis: A chemical reaction where are solubilized and large converted into simpler ;
• Acidogenesis: A biological reaction where simple monomers are converted into volatile ;
• Acetogenesis: A biological reaction where volatile fatty acids are converted into acetic acid, carbon dioxide, and hydrogen
• Methanogenesis: A biological reaction where are converted into methane and carbon dioxide, while hydrogen is consumed.

Anaerobic digestion is a complex Biochemistry process of Biology mediated reactions by a consortium of to convert into methane and carbon dioxide. It is a stabilization process that reduces odor, , and waste volume.

Hydrolysis bacteria form a variety of Redox end-products from the fermentation of a given substrate. One fundamental question that arises concerns the Metabolism features that control carbon and electron flow to a given reduced end-product during pure culture and mixed Methanogenesis cultures of hydrolytic bacteria. Thermoanaerobium brockii is a representative Thermophile, hydrolytic bacterium, which ferments glucose, via the Embden–Meyerhof Parnas Pathway. T. brockii is an atypical hetero-lactic acid bacterium because it forms molecular hydrogen (Dihydrogen), in addition to lactic acid and ethanol. The reduced end-products of glucose fermentation are Enzyme formed from pyruvate, via the following mechanisms: lactate by fructose 1-6 all-phosphate (F6P) activated lactate dehydrogenase; H2 by pyruvate ferredoxin oxidoreductase and hydrogenase; and ethanol via NADH- and NADPH-linked alcohol dehydrogenase.Marchaim, U. (1992). FAO Agricultural Services Bulletin – 95: Biogas process for sustainable development, FAO – 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 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 (, , and ) are depolymerization into soluble compounds by hydrolytic enzymes (, , , and ). The hydrolyzed compounds are fermented into volatile fatty acids (acetate, propionate, butyrate, and lactic acid), neutral compounds (ethanol, methanol), ammonia, hydrogen and carbon dioxide. 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. 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 is one of the main reactions of this stage, in this, the intermediary produced are metabolized to acetate, hydrogen and carbonic gas by the three main groups of bacteria:

• ;
• ; and
• .

For the acetic acid production are considered three kind of bacteria:

• Clostridium aceticum;
• Acetobacter woodii; and
• Clostridium termoautotrophicum.

Winter y Wolfe, in 1979, demonstrated that A. woodii in syntrophic association with Methanosarcina produce methane and carbon dioxide from 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 and Clostridium formiaceticum are able to reduce the carbonic gas to acetate, but they do not have which inhabilite the hydrogen use, so they can produce three molecules of acetate from fructose. Acetic acid is equally a co-metabolite of the organic substrates fermentation (sugars, glycerol, lactic acid, etc.) by diverse groups of microorganisms which produce different acids:

• Propionate bacteria (propionate + acetate);
• Clostridium (butyrate + acetate);
• Enterobacteria (acetate + lactate); and
• Hetero-fermentative bacteria (acetate, propionate, butyrate, valerate, etc.).

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