The microbial degradation of a cutting oil concentrate

Abstract

Using cultures of E. oleovorans.the concentration of fatty acids has been shown to increase with time. As the concentration of fatty acids increases, the rate of saturate degradation decreases. If the fatty acids are removed from the medium, an immediate rise in population is noted. Total protein as measured by the method of Lowry has proved to be a reliable indicator of the microbial population and indirectly, the degradation of the saturate fraction. The analysis of total protein is superior in reliability and ease of assay to viable plate counts and dissolved oxygen measurements. In the systems employed, hexadecane has proved to be inadequate as a "model" hydrocarbon. Growth was very poor on n-hexadecane, and in cultures of P. oleovorans hexadecanoic acid was shownto accumulate.

Cimperial #12D, a cutting oil concentrate, was degraded by cultures of Pseudomonas oleovorans and P. fluorescens. In addition the cutting fluid was degraded by a controlled mixed culture composed of seven isolates obtained from Lake George, New York. Degradation ofthe saturate fraction was used as an indicator of cutting oil degradation. Cimperial #12D is 62% saturates, 13% aromatics, 13% polar oils and 12% asphaltenes and insoluble oils. Quantification of saturate degradation and identification of saturate components was obtained by analyses using gas-liquid chromatography (GLC). A Tracer Microtek-220 equipped witha flame ionization detector was used throughout. Analyses were run in a temperature programmed mode, 70° - 325°C at 20°/min. The column used was a 6' x 1/4" 0.D. glass U-tube containing 3% OV-1 on 100/120 mesh acid washed Chromosorb P. Cultures of P. oleovorans showed the greatest amount of saturate degradation (60%) in a 21 day period. In addition to the initial saturate degradation, a secondary degradation of the aromatic fraction was noted after 12 days. The amount of saturate degradation observed with both P. oleovorans and P. fluorescens can be at least doubled by adsorbing the cutting oil to an inert substance (Celite). In mixed cultures of P. fluorescens and P. oleovorans one organism becomes dominant (P. fluorescens) and the degradation profile noticed is that characteristic for the dominant organism. By the use of GLC employing a column of 10% EGSS-X on 100/120 mesh Gas Chrom W, fatty acid methyl esters (FAMEs) could be detected. Prior to injection, the fatty acids were converted to their respective FAMEs by 10% BCl3 in methanol.