Degradation of phenol by Rhodococcus erythropolis UPV-1 immobilized on Biolite in a packed-bed reactor.

A strain of Rhodococcus erythropolis has been isolated and identified by 16S rRNA sequencing. Cells acclimated to phenol can be adsorbed on the external surface of beads of the ceramic support Biolite where they grow forming a network of large filaments. Exponentially-growing cells were adsorbed faster than their stationary-phase counterparts. Immobilization resulted in a remarkable enhancement of the respiratory activity of cells and a shorter lag phase preceding the active phenol degradation. Under optimum operation conditions, the immobilized cells in a laboratory-scale column reactor packed with support beads were able to degrade completely phenol in defined mineral medium at a maximum rate of 18 kg phenol m(-3) per day. The performance of the bioreactor in long-term continuous operation was characterized by pumping defined mineral medium which contained different concentrations of phenol at different flow-rates. Once phenol biodegradation in defined mineral medium was well established, an industrial wastewater from a resin manufacturing company, which contained both phenol and formaldehyde, was tested. In this case, after wastewater conditioning (i.e. pH, nitrogen source and micronutrient amendments) the immobilized cells were able to remove completely formaldehyde and to partly biodegrade phenols at a rate of 1 kg phenol m(-3) per day.