Acid producing bacteria

Acid producing bacteria (APB s) are those microorganisms whose metabolism results in the production of organic or inorganic acids. Examples of these organisms include Clostridium aceticum, that produces acetic acid, and Thiobacillus thiooxidans that produces sulfuric acid. Both of these organisms can contribute towards MIC of metal surfaces (Little et al, 1991). 

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Lactic acid-producing bacteria associated with fermented dairy products have been found to produce antibiotic-like compounds caUed bacteriocins. Concentrations of these natural antibiotics can be added to refrigerated foods in the form of an extract of the fermentation process to help prevent microbial spoilage. Other natural antibiotics are produced by Penicillium wqueforti the mold associated with Roquefort and blue cheese, and by Propionibacterium sp., which produce propionic acid and are associated with Swiss-type cheeses (3). 

Virtually all metallurgies can be attacked by corrosive bacteria. Cases of titanium corrosion are, however, rare. Copper alloys are not immune to bacterial attack however, corrosion morphologies on copper alloys are not well defined. Tubercles on carbon steel and common cast irons sometimes contain sulfate-reducing and acid-producing bacteria. Potentially corrosive anaerobic bacteria are often present beneath... 

The selective utilization of prebiotics by some, but not all, of the resident species alters the assemblages, densities and metabolic activities of the GIT bacteria. Of importance is the ability of prebiotics to increase the proportion of the resident bacteria represented by the lactic acid producing bacteria (LAB), resulting in changes of GIT and systemic functions (Swanson et al.. 

Electrochemical impedance, weight loss, and potentiodyne techniques can be used to determine the corrosion rates of carbon steel and the activities of both sulfate-reducing bacteria and acid-producing bacteria in a water injection field test. A study revealed that the corrosion rates determined by the potentiodyne technique did not correlate with the bacterial activity, but those obtained by electrochemical impedance spectroscopy (EIS) were comparable with the rates obtained by weight loss measurements [545]. 

Duff, R. B., Webley, D. M. Scott, R. O. (1963). Solubilization of minerals and related materials by 2-ketogluconic acid-producing bacteria. Soil Science, 95, 105-14. 

Outline the metabolic pathways that are utilized by acetic acid-producing bacteria (acetogens) in the stoichiometric conversion of one molecule of glucose into three molecules of acetic acid. Indicate briefly the nature of any unusual coenzymes or metalloproteins that are required. 

Propionic (propanoic) acid-producing bacteria are numerous in the digestive tract of ruminants. Within the rumen some bacteria digest cellulose to form glucose, which is then converted to lactate and other products. The propionic acid bacteria can convert either glucose or lactate into propionic and acetic acids which are absorbed into the bloodstream of the host. Usually some succinic acid is also formed. 

Food can be preserved by fermentation using selected strains nf yeast, lactic acid-producing bacteria, or molds. The production of ethanol, lactic and other organic acids, and anlimicrobial agents in the food, along with the removal of fermentable sugars, can yield a product having an extended shelf life. 

Different groups of microorganisms participate in this anaerobic conversion. First, extracellular enzymes of hydrolytic bacteria liquefy the polymenic and insoluble substances. The produced monomers are then further degraded by acid-producing bacteria to acetic acid, H2, C02 etc. These metabolites are the substrate for methane-producing bacteria. The end product, a gas mixture of 70 % methane and... 

A number of glutamic acid-producing bacteria are known, for example,... 

The simulations presented are for the conversion of acetic acid to microorganisms, methane, and carbon dioxide. Yields will be diflFerent for other volatile acids, especially noticeable being the increased ratio of methane to carbon dioxide produced as the length of the carbon chain increases. For field digesters utilizing complex substrates it would also be necessary to include the carbon dioxide generated by the acid-producing bacteria. 

In a field digester these steady-state values would also be affected by the fact that most of the volatile acids and cations (NH4 ) would be generated internally with some carbon dioxide being produced by the acid-producing bacteria. Acids other than acetic are also formed, and it is of interest to compare the steady state conditions for other volatile acids with those of acetic. The formulas for converting propionic and butyric acids to microorganisms, methane, and carbon dioxide are given in Equations 32 and 33. 

Persson A, Jonsson A-S, and Zacchi G. Separation of lactic acid-producing bacteria from fermentation broth using a ceramic microfiltration membrane with constant permeate flow. Biotechnol. Bioeng. 2001 72(3) 269-277. 

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