[show abstract][hide abstract] ABSTRACT: This work aimed to evaluate the aerobic biodegradation of butanol/diesel oil blends (5, 10, 15, 20%, v/v) in comparison to the biodiesel/diesel oil blend (20%, v/v). Respirometric experiments simulating the contamination of natural environments (soil and water from a river) were carried out in biometer flasks (250 mL) used to measure microbial carbon dioxide (CO 2) production. The automated turbidimeter Bioscreen C was used to follow the growth of Pseudomonas aeruginosa LBI on butanol/diesel oil blends. A redox indicator (2,6-dichlorophenol indophenol -DCPIP) test was used to evaluate the capability of four inocula to biodegrade the blends with 20% (v/v). The experiment which simulated the soil contamination demonstrated that butanol is less biodegradable than diesel oil, and for this reason the increase in the portion of butanol in the butanol/diesel blend from 5 to 20% had negative effects on biodegradation. While in soil the biodiesel/diesel blend was more easily biodegraded than the butanol/diesel blend, in water this order was the inverse. The insoluble fuels (diesel and biodiesel) were poorly biodegraded in water and the biodegradation of the butanol/diesel blend was favored by the water solubilization of the butanol, which enhances the bioavailability of this compound. On the other hand, initial concentrations of butanol in the water higher than 10 mL L -1 inhibited the cell growth of the tested microorganisms. Thus, butanol toxicity presumably had a significant effect on the degree of biodegradation of the fuel blends.
AFRICAN JOURNAL OF BIOTECHNOLOGY 11/2010; 9:7094-7101. · 0.57 Impact Factor
[show abstract][hide abstract] ABSTRACT: This work is aimed to assess the aerobic biodegradation of biodiesel/diesel blends (0, 2, 5, 20 and 100%, v/v) by Candida viswanathii. The biodegradation potential of the inoculum was assessed with the redox indicator 2,6-dichlorophenol indophenol (DCPIP) test and with respirometric experiment in biometer flasks (250 mL) used to measure the microbial CO 2 production. In the latter, the inoculum was added to a contaminated soil with the blends (addition of 50 mL of fuel/Kg of soil from a non-contaminated site). C. viswanathii was able to increase significantly (approximately 50% in terms of CO 2 production) the biodegradation in soil of biodiesel/diesel blends and neat biodiesel since it preferable biodegrades biodiesel. Without inoculum the biodegradation of diesel oil was higher than biodiesel and blends (47.3, 51.1, 5.7 and 22.1% in terms of CO 2 production by B2, B5, B20 and B100, respectively) presumably due to the presence of the antioxidant terc-butyl-hydroquinone (TBHQ) in the biodiesel.
AFRICAN JOURNAL OF BIOTECHNOLOGY 07/2009; 8:2774-2778. · 0.57 Impact Factor
[show abstract][hide abstract] 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 the Bartha and Pramer 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. Bioremediation, biodegradability experiments, commercial oil diesel, weathered diesel oil.