Abstract:
A survey of jet Fuel in New Zealand revealed microbial contamination in tankships, ground storage tanks, aircraft tanks, and throughout the fuel distribution system. A filtration method using two Whatman No.5 filter papers was found superior to other methods of isolation. The principal contaminant was Cladosporium resinae, which was isolated from 111 of 116 samples without EGME (ethylene glycol monomethyl ether) and from 19 of 39 samples with EGME. Penicillium spp. and a few other fungi were also widespread.
Spore germination studies showed glucose, ammonium sulphate or ammonium chloride, and sodium di-hydrogen phosphate to be the best sources of carbon, nitrogen and phosphate respectively. Spore germination was stimulated by surfactant concentration, Triton X-100.
Growth of C. resinae was affected by shape and size of vessels, shaking and low temperature. There was an initial lag-phase in the growth of all isolates in kerosene. C. resinae preferentially utilised the lower chain n-paraffins octane to decane. Aliphatic hydrocarbons supported better growth than aromatic hydrocarbons.
Prolonged immersion of spores in kerosene or water affected the viability of spores, more so in kerosene than in water. The anti-static agent (AGA3) was not inhibitory while EGME was fungistatic to germinating spores, the latter was fungicidal to immersion of spores in kerosene. EGME was not inhibitory at low concentrations and stimulated growth of C. resinae when glucose and ammonium as chloride or sulphate were added to Bushnell-Haas salt solution.
Corrosion of aluminium alloy was encouraged by surfactant concentration, except with By-prox. Corrosion was evidenced by pits and exfoliation when C. resinae was in contact with the alloy, pits were also present in the absence of C.resinae .
Metabolic products determined from the growth of C. resinae in kerosene were amino acids, glutamine and serine being predominant, extracellular amino acids or peptides, proteins, lipids and the pigment. Of the lipids the principal fatty acids were 16:0, 18:1 and 18:2. The pigment produced by C. resinae was extracted for the first time, and the spectral analyses of the four main fractions showed them to have similar characteristics as the total pigment.
The fine structure of spores of C. resinae consisted of a thick cell wall overlying a plasma membrane composed of a trilamellar layer system. Spores were uninucleate containing many structures, unidentified membrane bound bodies and membraneous systems.
Studies on other micro-organisms showed that of 34 organisms isolated from jet fuel, only six grew in Bushnell-Haas salts and kerosene with and without 0.1 and 0.15% EGME. Immersion of mixed spores in kerosene revealed C. resinae to remain viable longer in kerosene with and without EGME ,and better able to survive and grow in kerosene than any other fungus.
