In México, there are extensive areas polluted by oil spills. Currently, bioremediation technologies have been developed, using microorganisms to clean up oil sites. In this study, we evaluated the development of a hydrocarbonoclastic bacterial strain, using a completely randomized 3x3x4 factor arrangement: three temperatures, three pH, and four nutrients. We collected samples of soil contaminated with 3.45 x 10 5 mg kg -1
México has extensive areas that have been impacted by oil spills for several decades. Current bioremediation technologies mostly used microorganisms to decontaminate sites with hydrocarbons. This research evaluated the conditions for the optimal development of the strain of a hydrocarbonoclastic fungus, which was found in samples of soil contaminated with 4.0 × 10 5 mg·kg −1 of Total Petroleum Hydrocarbons (TPH). A completely randomized experimental design with a 3 × 3 × 4 factor arrangement was used: three levels of temperature (T 1 = 29˚C, T 2 = 35˚C and T 3 = 40˚C), three of pH (pH 1 = 3.5, pH 2 = 5.0 and pH 3 = 6.0) and four nutrients (N 1 = Urea, N 2 = Triple-17, N 3 = Nitrophoska-Blue and N 4 = Pure-Salts). Total fungi were isolated from the sampled soil and were sown in a combined carbon medium for hydrocarbonoclastic fungi and a strain was selected to be adapted to a liquid mineral medium. The selected strain was classified as Penicillium sp. Analyses of variance and mean tests were performed, using the SPSS-11.0 statistical software. The microorganisms showed the highest population growth in the treatment N 2 pH 2 T 1 , which reached a value of 2.1 × 10 6 CFU·mL −1 in a biorreactor. To reach it, by bioaugmentation, the same development of Penicillium sp. in a conditioned soil would allow to implement a bioremediation strategy with great potential to retrieve soil contaminated with hydrocarbons both in Tabasco and in general in Mexico.
Biosurfactants are metabolites produced by microorganisms during their growth and reproduction. They are amphiphilic molecules capable of modifying surface and interfacial tension. A petrophilic, nitrogen-fixing, phosphorus-solubilizing, and biosurfactant-producing bacterial strain was isolated and characterized. The isolated strain was cultivated in Kim medium with a C:N ratio of 2:1, from which its growth kinetics was determined. Samples of the culture broth were taken at different times and the collapsed drop, oil dispersion and emulsification index tests were performed. Maximum culture growth occurred at 72 h. The biosurfactant was extracted from the crude cell-free broth using a mixture of solvents and a yield of 2.21 g/L was obtained. Thin-layer chromatography and FT-IR analyzes revealed the presence of a lipopeptide biosurfactant. Tensiometry tests showed that the biosurfactant was able to lower the surface tension of water from 72 mN/m to 40 mN/m and the critical micelle concentration was 0.058 (w/w). Probit analysis for toxicity determination showed that there was no weight loss in Eisenia foetida specimens in a range between 10000 and 50000 ppm.
The present project explains how crude biodiesel (crude BD) has been obtained by using coconut oil and ethyl alcohol as well as sodium hydroxide as a catalyst. The coconut oil was extracted with water which was submitted to evaporation afterwards. This experiment was carried out by adding the coconut oil in a 500 mL glass flask. The catalyst was dissolved in ethyl alcohol and mixed together with the coconut oil. Once obtained the mixture, this was stirred for 25 minutes at temperatures from 20, 30, 40, 50 to 60 °C. During the reaction, two phases were formed: crude biodiesel (top layer) and crude glycerol (bottom layer). The characterization was done by determination of pH (using an electrode located in the top layer connected to a computer by RS-232 interface system). When the separation concluded, the crude BD was rinsed in order to remove the catalyst. The characterization of washed biodiesel was determined by density and Saybolt viscosity. Fourier Transform Infrared (FTIR) analysis was also made. The results by FTIR indicated the two functional groups of fatty acid ethyl esters (C=O, 1733 cm-1 and C-O, 1154 cm-1) and the OH wide band group of glycerol at 3400 cm-1. When the reaction time ended, the maximum pH value registered was 12.7. The values for pH, density and Saybolt viscosity were acceptable for crude BD and crude glycerol.
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