| Biodegradation of biodiesel from an industrial impacted sandy soil (Guayanilla Bay, Puerto Rico) and bacterial diversity was evaluated. Soil samples were amended with 2,500 mg/Kg of biodiesel and incubated during 41 days in laboratory conditions. Biodegradation by natural attenuation and enhanced of biodegradation by biostimulation with inorganic nutrients were examined. In addition, degradation of regular diesel (1,500 mg/Kg) and a mixture of diesel with biodiesel were examined. The biodegradation was measured by CO2 evolution ( EPA 560/82-003) and gas chromatography method (EPA 8015B ). The bacterial diversity of culturable bacteria populations was determinate by carbon utilization profiles (BiologRTM), ability to use biodiesel as the sole carbon source and molecular techniques including amplified ribosomal DNA restriction analysis (ARDRA) and 16S rDNA sequence analysis. Gas chromatography showed partial removal of biodiesel (80%) and diesel (57%) in the natural attenuation treatment. The CO2 evolution indicated that both rate and extent of biodiesel mineralization is greater than diesel indicating that biodiesel is more biodegradable. The removal of either diesel or biodiesel was enhanced after inorganic nutrient addition. A total of 36 bacterial populations were isolated of 26 distinctive genetic and physiological groups. Only 50% (18/36) of all bacterial populations grew in a medium with biodiesel constituents as sole carbon source. In general, the community was dominated mainly by Gram positive bacilli. Sequence analysis of the 16S rDNA showed close relation with Bacillus thuringiensis, B. subtilis, B. megaterium, Paenibacillus latus and Micrococcus luteus, of the Firmicutes and Actinobacteria divisions which are widely recognized to be known hydrocarbon degraders in the environment. |
