Acinetobacter radioresistens metabolizing aromatic compounds. 1. Optimization of the operative conditions for phenol degradation.

A strain of Acinetobacter radioresistens was able to utilize phenol as the only carbon and energy source, after an acclimatization period of 3 days in which increasing phenol concentrations from 50 to 200 mg/l were supplied. At 30 degrees C, the complete phenol utilization in batch degradation tests occurred in 2.5-3 h at pH 7 and 8, but it increased strongly at pH 6 (over 40 h). No microbial growth was detected at 40 degrees C, while at 20 degrees C (pH 7-8) the time necessary for complete phenol degradation was about twofold longer than that at 30 degrees C (pH 7-8) revealing a good capability of the strain as a seed-micro-organism for enhancing phenol degradation. The bacterial growth in acclimatized cultures, evaluated with the viable cell count, always displayed a trend consistent with the use of phenol as a substrate with an eventual lag phase and then an exponential phase, while in the non-acclimatized cultures an initial stage of cellular death was observed.