Exogenous phenazine allows biofilm stability but retards biodegradation of recently WLO-contaminated aqueous system

Each year, millions of liters of lubricating oil are consumed worldwide, and more than 50% of Total Petroleum Hydrocarbons (TPH) enter the environment through spills or improper disposal. Numerous strategies are applied to remediate oil-contaminated sites, and each scenario contributes to assessing the maximum efficiency of available cleanup approaches. This study evaluated, on a laboratory scale, the effect of phenazine methosulfate (PMS) on Waste Lubricating Oil (WLO) removal by P. aeruginosa. Microcosms were contaminated with WLO containing 448,000 mg·kg⁻¹ of TPH. WLO: aqueous phase ratios of 1:40, 1:20, and 1:10 were tested, all supplemented with PMS at 5 µg·mL⁻¹. After 20 days of incubation at 29°C, greater WLO removal was observed in microcosms without PMS (33.8-37.8%), whereas PMS-amended systems removed only 9.9-15.3% (p > 0.05) possibly due to WLO composition or PMS interacting with alternative cell pathways. In both treatments, the inoculated cells were not adversely affected by the stressful conditions and established stable biofilms. This is the first report describing the effect of PMS on P. aeruginosa biofilm formation during WLO biodegradation under recent-contamination conditions. These findings indicate that combining bioaugmentation with exogenous phenazine addition should be avoided in the initial treatment phase.