[Microbial growth and fuel tanks hazards (author's transl)]

Fuel tanks are susceptible to contain a microflora consisting of bacteria and fungi which appear as sludge at the bottom of the tanks. This microflora is quite variable. Various strains of microorganisms were isolated, belonging to the following genera: Pseudomonas, Acinetobacter, Mycococcus, Penicillium, Aspergillus, Candida, Cladosporium. These strains are generally adapted to hydrocarbons though non adapted strains are also found, which develop with the help of metabolites excreted by the adapted strains or their lysates. The microorganisms use mostly the paraffinic fraction of the fuel. Some strains attack also aromatic hydrocarbons. Contaminated fuels were found to contain noticeable amounts of fatty acids. The study of the production of organic acids by strains isolated from fuel tanks shows that many strains are able to excrete organic acids. The nature of the fatty acids produced depends upon the strain: in some dases they correspond to the branched paraffins contained in the fuel. The comparison of microbial growth and organic acid production in mixed cultures with fuel with various quantities of fuel to water shows that the large amount of fuel compared to water in a fuel tank can be responsible for the importance of microbial growth and organic acids.