Bacterial Communities in Effluents Rich in Phenol and Their Potential in Bioremediation: Kinetic Modeling.

Phenol is used in the manufacturing process of phenolic resins from which residues remain that must be sent for confinement. For that reason, in this study, the wastewater of a resin factory was analyzed to isolate the bacteria present, identify them by molecular methods and finally evaluate their impact on bioremediation treatment. A total of 15 bacteria were isolated, of these, eight belong to the genus Bacillus spp. All bacteria were individually multiplied and inoculated in clusters in 15 L reactors which were carefully monitored for pH, electrical conductivity, chemical oxygen demand and temperature. The acquired data were analyzed using ANOVA with repeated measurements. The first test revealed that native bacterial communities reduce the phenol content by up to 20% and COD by 49%, which is significant with respect to the reactor not being inoculated with bacteria. Furthermore, when a mathematical model was applied to the reactors, it was shown that the bacteria require an adaptation time of approximately 100 h. A second test where the inoculation was interspersed with the addition of lime as a flocculant showed that, even though the reduction in phenol and COD was lower than in the previous test, the difference between treatments and control is statistically significant (α ≤ 0.05).

Biodegradación de fenol en aguas tratadas de la industria petrolera para re-uso en cultivos agrícolas / Biodegradation of phenol in treated water from the oil industry to re-use in agricultural crops

ResumenLa explotación del petróleo y el uso de sus derivados han contribuido para el desarrollo tecnológico a nivel mundial. Esta actividad, no obstante, genera muchos subproductos los cuales atentan contra la salud del ambiente. Las aguas de producción, por ejemplo, pueden contener trazas de metales pesados e hidrocarburos, razón por la cual deben ser reincorporadas de forma adecuada al ambiente. En este trabajo, se aislaron, caracterizaron e identificaron molecularmente ocho bacterias en base a su capacidad para degradar fenol. Primero, se evaluó el crecimiento y la degradación de fenol bajo diferentes concentraciones (500, 800 y 1 200 mg / L), y posteriormente se emplearon diseños estadísticos para la selección de condiciones óptimas de degradación. Los resultados mostraron que las ocho cepas evaluadas fueron capaces de usar el fenol como fuente única de carbono; no obstante, las cinéticas de degradación y la máxima tolerancia de las cepas al fenol variaron ampliamente. Debido a su tolerancia y capacidad para metabolizar fenol, la cepa Pseudomonas sp. Sps1 fue seleccionada para posteriores estudios. Mediante el uso de un diseño de Plackett Burman y un diseño factorial fraccionado en el cual diferentes fuentes de carbono, nitrógeno, y fósforo fueron evaluadas y degradación de fenol fue usado como variable de respuesta, fue posible seleccionar las condiciones óptimas para la degradación de fenol por Sps1. Finalmente, se emplearon estas condiciones para evaluar la degradación de fenol en aguas de re-uso provenientes directamente de la industria petrolera. Los resultados, mostraron que la bioestimulación favoreció el proceso de degradación del fenol comparado con el control. En conclusión, en este estudio se demostró que la bioaumentación con bacterias nativas acompañada de bioestimulación generan una tecnología económica y ambientalmente amigable para la remoción de contaminantes en aguas residuales tratadas de la industria petrolera.

AbstractOil exploitation and the usage of its derivatives have undeniably contributed to the technological advance worldwide. This industrial activity, however, generates several by-products that can threaten environmental sustainability. Seawage, for example, can contain organic pollutants and heavy metals; therefore, its deposition must be preceded by adequate water treatment. In this study, we isolated, characterized, and molecularly identified eight bacteria on the basis of their capability to degrade phenol. First, we determined the rates of bacterial growth and phenol degradation using different concentrations of the aromatic hydrocarbon (500, 800 and 1 200 mg / L), and then used sequential statistical designs to select optimal conditions for its degradation. Results showed that all isolated strains were capable of degrading phenol as the sole carbon source; the degradation kinetics and phenol tolerance, however, widely varied among strains. We chose the strain Pseudomonas sp. Sps1 for further studies due to its remarkable tolerance and capability to degrade phenol. By using a Plackett Burman design, followed by a fractionated factorial design in which several carbon, nitrogen, and phosphorus sources were evaluated, and phenol degradation was used as the response variable, we found optimal conditions for phenol degradation by Sps1. Finally, we compared phenol degradation in seawage by the use or not of the optimal conditions established by the statistical methods. Results showed that biostimulation dramatically increased phenol degradation compared with the control. In conclusion, we found that bioaugmentation with the native bacteria Sps1 and a statistically-based biostimulation approach provided an economically and environmentally friendly alternative for the removal of pollutants from oil industry sewage.

Phylogeny and polycyclic aromatic hydrocarbons degradation potential of bacteria isolated from crude oil-contaminated site.

This study employed the use of 16S rRNA gene sequence analysis to identify three of four native bacterial strains isolated from crude oil-contaminated site in Poza Rica, Veracruz, Mexico. The identified bacteria were Ochrobactrum intermedium, Pandoraea pnomenusa and Ochrobactrum sp., but SA2-09 strain was not identified. The ability of the isolates to degrade polycyclic aromatic hydrocarbons (PAHs) was evaluated at 31.61 and 54.52 mg/kg PAHs in soil, when used as crude oil in soil microcosm during 80 days of incubation at 30°C. The results demonstrated that O. intermedium biodegraded many PAHs, including the high molecular weight (HMW) PAHs fluoranthene (100% equivalent 0.24 mg/kg), benzo [b] fluoranthene (81.8% equal 0.18 mg/kg), Benzo[a]pyrene (87.0%, 0.20 mg/kg) and Benzo[g,h,i]perylene (52.7%, 0.39 mg/kg). P. pnomenusa had a degradation profile of HMW PAHs, which was similar to O. intermedium, while Ochrobactrum sp. and the strain SA-09 exhibited lower degradation rates of HMW.

Native soil bacteria isolates in Mexico exhibit a promising antagonistic effect against Fusarium oxysporum f. sp. radicis-lycopersici.

Sinaloa state accounts for 23% of Mexico's tomato production. One constraint on this important crop is the Fusarium crown and root rot, caused by Fusarium oxysporum f. sp. radicis-lycopersici, which has been reported to reduce crop yield by up to 50%. In this study, we set out to identify bacterial populations which could be used to control this disease through natural antagonism. Five tomato rhizospheric soil samples were collected, dried for 1-week, and homogenized. Sub-samples were used to prepare an aqueous solution used to isolate microorganisms in pure cultures. Organisms were purified and grown separately, and used to generate a collection of 705 bacterial isolates. Thirty-four percent from this bank (254 strains) was screened against Forl, finding 27 bacteria displaying in vitro Forl growth inhibition levels from 5% to 60%. These isolates belonged to the genus Bacillus and their 16Sr DNA sequences showed that they are closely related to seven species and they were putatively designated as: B. subtilis, B. cereus, B. amyloliquefaciens, B. licheniformis, B. thuringiensis, B. megaterium, and B. pumilus. One isolate belonged to the genus Acinetobacter. Two B. subtilis isolates (144 and 151) and one B. cereus isolate (171) showed the best antagonistic potential against FCRRT when evaluated on seedlings. Plate and activity assays indicate that these isolates include a diverse repertoire of functional antagonistic traits that might explain their ability to control FCRRT. Moreover, bacteria showed partial hemolytic activity, and future research will be directed at ensuring that their application will be not harmful for humans and effective against Forl in greenhouse or field conditions.