Biodegradability of commercial and weathered diesel oils

Abstract

This work aimed to evaluate the capability of different microorganisms to degrade commercial diesel oil in comparison to a weathered diesel oil collected from the groundwater at a petrol station. Two microbiological methods were used for the biodegradability assessment: the technique based on the redox indicator 2,6 -dichlorophenol indophenol (DCPIP) and soil respirometric experiments using biometer flasks. In the former we tested the bacterial cultures Staphylococcus hominis, Kocuria palustris, Pseudomonas aeruginosa LBI, Ochrobactrum anthropi and Bacillus cereus, a commercial inoculum, consortia obtained from soil and groundwater contaminated with hydrocarbons and a consortium from an uncontaminated area. In the respirometric experiments it was evaluated the capability of the native microorganisms present in the soil from a petrol station to biodegrade the diesel oils. The redox indicator experiments showed that only the consortia, even that from an uncontaminated area, were able to biodegrade the weathered diesel. In 48 days, the removal of the total petroleum hydrocarbons (TPH) in the respirometric experiments was approximately 2.5 times greater when the commercial diesel oil was used. This difference was caused by the consumption of labile hydrocarbons, present in greater quantities in the commercial diesel oil, as demonstrated by gas chromatographic analyses. Thus, results indicate that biodegradability studies that do not consider the weathering effect of the pollutants may over estimate biodegradation rates and when the bioaugmentation is necessary, the best strategy would be that one based on injection of consortia, because even cultures with recognised capability of biodegrading hydrocarbons may fail when applied isolated.

Investigation about the efficiency of the bioaugmentation technique when applied to diesel oil contaminated soils

“…This behavior was not observed in treatment 6 possibly due to a competition caused by the exogenous microorganisms. Chromatographic analyses of ASP and SB samples (Table 4) revealed that at these sites, the diesel oil was already weathered, i. e. the fuel had their characteristics altered by physical-chemical and biological mechanisms due to the large period of exposure of these compounds to the environmental conditions (Mariano et al, 2008b). Diesel oil contains 2000 to 4000 hydrocarbons, a complex mixture of normal, branched and cyclic alkanes, and aromatic compounds (Gallego et al, 2001), which cannot be totally separated by gas chromatography.…”

<b>Petroleum biodegrading and co-resistance to antibiotics by <i>Serratia marcescens</i> strain isolated in Coari, Amazonas

“…According to Bidoia et al (2010), DCPIP is a reversible indicator, returning to its original coloration after reduction occurs. Mariano, Bonotto, De Angelis, Pirôllo, and Contiero, (2008) evaluated the rate of biodegradation of diesel and biodiesel by the colorimetric method with the redox indicator DCPIP, establishing the final time of the experiment by altering the color of the medium, from blue (oxidized) to colorless (reduced). Varjani and Upasani (2013), when assessing the hydrocarbon degradation by a bacterial consortium, recorded the lowest discoloration time of the medium in 120 hours, out of a total of 144 hours.…”

Isolation and identification of bacterial consortia responsible for degrading oil spills from the coastal area of Yanbu, Saudi Arabia

“…[11] Similar works have reported that bacterial cultures can completely reduce DCPIP at 75, 87, 125 and 138 h for mineral oil, used oil, semi-synthetic oil and synthetic oil, respectively. [30] Mariano et al [31] performed the DCPIP assay in order to confirm that diesel oil could be degraded by bacterial consortia. Our isolates caused a colour change from blue to colourless, indicating that they have the ability to degrade crude oil.…”