Fungal biodeterioration of synthetic metal working fluids

A survey was undertaken to determine the relative incidence of fungal biodeteriogens in contaminated in—service samples of synthetic and oil emulsion metal working fluids, and a list of isolates is submitted. A technique for assessing the concentration of surface—active components of both synthetic and oil emulsion metal working fluids is described. Results obtained using this technique provided evidence of surfactant depletion in oil emulsion fluids as a result of growth of a mixed fungal inoculum, but this effect was not recorded when these isolates were grown in synthetic fluids. Synthetic metal working fluds of known composition were formulated and the ability of selected fungal isolates to utilise both these fluids and the individual components thereof as sole sources of carbon and nitrogen was assessed. The metal working fluid components triethanolamine and diethanolamine borate were found to be readily available nutrient sources for growth of the isolates, the extent of growth being limited by the availability of carbon rather than nitrogen. Varying the initial pH of the medium was found to have no significant effect upon the extent of growth recorded at initial pH values of 7.0, 8.0 and 9.0. The use of respirometric techniques provided evidence to suggest that some of the enzymes involved in the fungal degradation of synthetic metal working fluid components might be inducible. The effect of fungal growth upon the composition of the complete synthetic metal working fluids was determined using the techniques of nuclear magnetic resonance spectroscopy and gas—liquid chromatography linked mass spectrometry. Results obtained using these techniques also provided evidence of the depletion of the triethanolamine and diethanolamine borate components of the complete fluids as a result of fungal growth.