ACTIVITY OF SYNCHRONIZED CELLS OF A STEADY-STATE BIOFILM RECIRCULATEDREACTOR DURING XENOBIOTIC BIODEGRADATION

The maintenance of a steady-state biofilm in a continuous-flow fixed-b ed reactor, as a consequence of the reproduction-detachment of cells ( an interfacial cell physiology phenomenon of steady-state biofilm) dur ing the biodegradation of 2,4,6-trichlorophenol by Pseudomonas tells, was determined. After cell adhesion on an open-pore glass support, the biofilm was formed in a packed-bed recirculated reactor. After the st eady-state biofilm was reached, the mechanisms of the interfacial cell detachment (at the biofilm-liquid interface) were determined. It was established that (i) the hydrophobicity of immobilized sessile cells ( parent cells) increased (from 50 to 80%) as the dilution rate increase d, while the hydrophobicity of detached suspended cells (daughter cell s) remained constant (about 45%); and (ii) the immediately detached su spended cells showed a synchronized growth in about three generations. These results indicate that (i) the immobilized sessile and suspended detached cells grew synchronically at the end and at the beginning of the cell cycle, respectively; and (ii) the hydrophobicity difference of immobilized sessile and suspended detached cells permitted the cell detachment. Therefore, it is probable that independent of shear stres s (due to recirculated flow), the synchronized growth and hydrophobici ty of cells (which vary during the cell cycle) are the main factors pe rmitting the maintenance of a steady-state xenobiotic-degrading biofil m reactor (in which the overall accumulation of biofilm is determined by the average growth rate of the biofilm cells minus the rate of deta chment of cells from the biofilm).