Kinetics of biodegradation of diesel fuel by enriched microbial consortia from polluted soils

Abstract

Three microbial consortia were isolated from three polluted soils located at an oil refinery and acclimated to grow on diesel fuel as the sole carbon source. Batch experiments were then conducted with the three consortia to study the kinetics of diesel biodegradation. The effects of temperature (25, 30 and 35°C) and diesel concentration (0.5, 1 and 3 %) on the biodegradation of diesel were analysed. Several species were identified in the acclimated microbial consortia, and some of them appeared in more than one consortium. Thermal inhibition was observed at 35°C. In the rest of experiments, over 80 % of the substrate was degraded after 40 h of treatment. These results proved the good feasibility of using the polluted sites as sources of mixed consortia for hydrocarbon degradation. However, diesel degradation efficiencies and rates were very similar, suggesting that the acclimation process produced mixed consortia with very similar characteristics; in this context, origin of the soil sample was not a decisive factor. A simple Monod-type kinetic model was used to simulate the biodegradation process, and accurate results were obtained. The l max values were between 0.17 and 0.34 h -1 . The results of this study revealed that the consortia can function at high concentrations of hydrocarbons without any sign of growth inhibition, which is important for the design of bioreactors for wastewater treatment with high concentrations of fuel.

Combination of bioremediation and electrokinetics for the in-situ treatment of diesel polluted soil: A comparison of strategies

“…This consortium of microorganisms was maintained and enriched with Bushnell-Hass Broth (BHB) as the mineral medium (the composition of the medium per litre of deionised water was 0.20 g l −1 MgSO 4 , 0.02 g l −1 CaCl 2 , 1.00 g l −1 KH 2 PO 4 , 1.00 g l −1 (NH 4 ) 2 HPO 4 , 0.05 g l −1 FeCl 3 and 1.00 g l −1 KNO 3 ) and diesel hydrocarbon as the sole carbon source (1.0% v/v). After the enrichment process, some of the microorganisms in the consortium were identified, including Staphylococcus lentus, Stenotrophomonas maltophilia and Pseudomonas fluorescens, as reported in a previous work (Moliterni et al, 2012). According to previous studies, these species are commonly found in hydrocarbon-polluted soils.…”

“…However, the average diesel removal efficiency was only approximately 12%. In previous studies on diesel biodegradation using the same microbial consortium (Moliterni et al, 2012) and using the biobarrier (Mena et al, 2015), it was found that the biodegradable fraction of the diesel was approximately 70% (expressed as COD). Thus, only a small portion of the biodegradable fraction of the diesel hydrocarbons was removed through the Bio treatment in two weeks, which could be due to the slowness of the static in situ biological process.…”

“…Diesel was purchased from a petrol station in Ciudad Real, Spain, and characterized as previously reported (Moliterni et al, 2012). To artificially pollute the soil, the diesel was diluted tenfold in acetone before evenly distributing the solution drop by drop in a corresponding amount of kaolinite.…”

The Monod and a biphasic biodegradation kinetics of diesel hydrocarbons by a biofilm of Pseudomonas and the potential electromotive force involved

“…Continuous‐flow systems may need less time to consume the substrates of interest but batch studies may treat higher substrate concentrations without many of the problems associated with continuous‐flow designs. For example, our reactor system reached >95% degradation in only 1.5 h, whereas an aerobic consortia batch study needed 40 h to degrade >80% at an initial diesel concentration 3‐fold higher than ours . In this particular case, we used lower diesel concentrations since Monod kinetics can be applied only for low to intermediate pollutant concentrations.…”

“…For example, our reactor system reached >95% degradation in only 1.5 h, whereas an aerobic consortia batch study needed 40 h to degrade >80% at an initial diesel concentration 3-fold higher than ours. 34 In this particular case, we used lower diesel concentrations since Monod kinetics can be applied only for low to intermediate pollutant concentrations. In addition, a batch diesel degradation study at 30 ∘ C by a pure culture of the biosurfactant producing Gordonia alkanivorans diesel consumption and monitored cell dry weight at designated time intervals.…”