Bioavailability of soil-sorbed biphenyl to bacteria

Limited bioavailability of organic pollutants in soil may be a detriment to the successful application of bioremediation. The availability of soil-sor bed biphenyl to two biphenyl-degrading bacteria, Pseudomonas putida P106 an d Rhodococcus erythropolis NY05, was assessed using a kinetic mineralizatio n assay. Biphenyl was aged in four soils of different organic carbon (OC) c ontents (0.4-7.8%) for up to 274 days. With a biphenyl-soil contact time of 24 h, the initial mineralization rates (IMRs) ranged from 2.6 to 3.5 mu g. L-1.min(-1) for strain P106 and from 3.8 to 0.92 mu g.L-1.min(-1) for strai n NY05. These IMRs were higher than those of soil-free controls and those p redicted by a coupled desorption/biodegradation model, suggesting both stra ins of bacteria could access soil-sorbed biphenyl. For strain P106, bipheny l mineralization curves in slurries of four different soils were nearly coi ncident with those in soil-free systems containing the same total mass of b iphenyl. This strain appeared to have immediate and complete access to the pool of sorbed biphenyl. The extent of bioavailability of soil-sorbed biphe nyl decreased with increased aging. The decrease in availability was most p ronounced within the first 80 days. The effect of soil organic matter conte nt on bioavailability showed different trends for the two organisms.