Bacterial Growth As a Practical Indicator of Extensive Biodegradability of Organic Compounds

The proportionality of growth, as indicated by turbidity of cultures of Pseudomonas C12B, to the initial concentration of sodium dodecyl sulfate, dodecanol, or a mixture of C(10)-C(20) secondary alcohol sulfates, each provided as sole carbon source in basal mineral salts medium, was demonstrated. Subsequently, the direct correlation of culture turbidity as a growth indicator and degradation of sodium dodecyl sulfate and the C(10)-C(20) compounds was established. Degradation of these detergents was measured by the rise in surface tension and the decrease in methylene blue values, respectively. Turbidimetry was found to be a poor indicator of degradation of dodecanol in the early hours of culture, however, and did not correlate over a significant range with degradation of substrate. Viable cell counts did parallel dodecanol degradation as measured by gas-liquid chromatography. The use of bacterial growth as a reliable, quantitative, and easily measured parameter indicating biodegradability was suggested for those organic compounds which can be shown to serve as a carbon source for a bacterium.