The degradation of phenanthrene by a Beijerinckia species

The purpose of this study was to determine the effects of temperature and pH on the degradation rate of phenanthrene by a Beijerinckia sp.

Batch experiments were employed for the experimentation with a growth medium consisting of basic mineral salts, yeast extract (0.5 grams/liter), phosphate buffer (0.1 molar) and approximately 1.29 ppm phenanthrene.

The effects of temperature at a pH of 7.0 on the specific growth rate of the Beijerinckia was Arrhenius in form exhibiting an "activation energy" of growth of approximately 16 kilocalories/ gram-mole. The effect of temperature on phenanthrene degradation rate was non-Arrhenius, with phenanthrene degradation commencing at a temperature of approximately 19 °C and increasing rapidly to a temperature of approximately 25 °C. Between the temperatures of 25 °C and 29 °C the degradation rate remained essentially constant, and once the temperature was greater than 29 °C, the degradation rate declined rapidly. The maximum cell specific growth rate of 0.730 (hours)^-1 occurred at 30 °C ± 2 °C and a pH of 7.0 ± 0.20. The maximum phenanthrene degradation rate of 3.59 x 10^-11 milligrams of phenanthrene/cell hour occurred at 26 °C ± 2 °C and a pH of 7.0 ± 0.20.

The pH behavior of the experimental system at 25 °C exhibited a sharp maximum in terms of both specific growth rate and iv phenanthrene degradation rate. The optimum pH for growth and phenanthrene degradation was 7.0 ± 0.2.