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

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Microbial fuel cells (MFCs) are bioelectrochemical devices able to convert chemical energy into electricity. The selection of anodic pH and external resistances play a significant role in the overall performance of the device. This research presents the effect of operational conditions of the MFC using B. Subtilis in anode. The effect of pH and external resistance were determined by 3 2 full factorial design. Data were analyzed statistically by ANOVA and p ≤ 0.05 was considered statistically significant. The surface response analysis evidenced interaction and quadratic effect of the pH and external resistance on the power density generation. With a second-order polynomial model the optimum conditions of the system were determined. It maximized the power at pH of 8.6 and an external resistance of 220 Ω, delivering power density of 405 mW/m 2 . The chemical oxygen demand (COD) removal efficiency and coulombic efficiency (CE) were 82% and 15%, respectively. The maximum specific growth (µ) and substrate uptake (k 1 ) rate for electrochemically active bacteria (EAB) at optimum conditions were 0.19/h and 0.019/h respectively. These experimental results show the importance of the simultaneous effect of pH and external resistance, which is even more influential then if they were studied separately.

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Mangrove forests are ecosystems subject to contamination by oil spills. The objective of this study was to evaluate the development of Rhizophora mangle plants in soil contaminated with oil emulsified with surfactants. These ecosystems have diverse and economically valuable ecological functions. Mangrove soil and propagules were collected in southeastern Mexico. The propagules were sown under greenhouse conditions and the plants were grown for 3 months. Two bioassays were applied: (1) the soil was contaminated by oil emulsified with a biosurfactant synthesized by Azospirillum lipoferum, and (2) the soil was contaminated with oil emulsified with a surfactant based on pine essential oil. Emulsified oil was applied to the substrate in containers with 3-month-old plants until several concentrations were reached (0, 30,000, 40,000, 50,000, 60,000, and 70,000 ppm). Subsequently, 5 plants for each treatment were randomly extracted every 30 days for 12 months, and the stem length and diameter, root length, leaf area, and fresh and dry weights of the plants were evaluated. Plant development was evaluated through an analysis of variance and a test of means. At the end of the bioassay, the treatments with oil emulsified with pine oil yielded no surviving plants, whereas the treatments with oil emulsified with the biosurfactant yielded a 100% survival rate. Treatment with 30,000 ppm of oil emulsified with the biosurfactant yielded the greatest increases in the leaf area and total dry biomass. The heavy oil fraction concentration decreased by 93.9% with the 30,000 ppm treatment and by 82.64% with the 70,000 ppm treatment.

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.