A pilot study for monitoring changes in the microbiological component of metalworking fluids as a function of time and use in the system

This article describes the results of a pilot study to examine changes in the biological component of metalworking fluids (MWF) as a function of use. Fluid samples were taken from two newly charged systems, designated BT-7415 and BT-7707, at 1-week intervals for 8 weeks and characterized with respect to the kinds and numbers of bacteria present and presence of soluble protein in cell-free supernatants. In addition, lipid extracts of pelleted cells from fluids in BT-7415 were examined by gas chromatography/mass spectroscopy for the kinds and relative amounts of phospholipid fatty acids (PLFA) present. A total of 19 different bacterial species was cultured and identified, more than half (12/19) of which were gram-negative. Total colony-forming units (CFU) reached levels of 2.2 × 103/mL in BT-7415 and 2.4 × 105/mL in BT-7707. The most common genus isolated was Pseudomonas. Estimations of cell numbers based on total biomass from PLFA in samples from BT-7415 indicated 1.1 × 107/mL after 8 weeks of use. Both th...