Análisis ecofisiológico de la desnitrificación en presencia de acetato y tolueno
A contribution to the knowledge of denitrifying process in presence of toluene is presented. The effect of an easily degradable substrate such as acetate on toluene mineralization under denitrifying conditions was evaluated by means of consumption efficiencies, yield products and substrate specific...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2007 |
| País: | México |
| Institución: | Universidad Autónoma Metropolitana |
| Repositorio: | Repositorio Institucional de la UAM Iztapalapa |
| Idioma: | español |
| OAI Identifier: | oai:bindani.izt.uam.mx:ww72bb730 |
| Acceso en línea: | https://doi.org/10.24275/uami.ww72bb730 |
| Access Level: | acceso abierto |
| Palabra clave: | info:eu-repo/classification/LEM/Biotechnology info:eu-repo/classification/LEM/Sewage -- Purification -- Nitrogen removal info:eu-repo/classification/LEM/Denitrification info:eu-repo/classification/LEM/Tolueno info:eu-repo/classification/LEM/Toluene info:eu-repo/classification/LEM/Desnitrificación info:eu-repo/classification/LEM/Biotecnología info:eu-repo/classification/LEM/Aguas residuales -- Purificación -- Eliminación de nitrógeno info:eu-repo/classification/cti/6 |
| Sumario: | A contribution to the knowledge of denitrifying process in presence of toluene is presented. The effect of an easily degradable substrate such as acetate on toluene mineralization under denitrifying conditions was evaluated by means of consumption efficiencies, yield products and substrate specific consumption rates. Molecular techniques such as denaturing gradient gel electrophoresis (DGGE) and real-time PCR analysis were used in order to determinate whether a relationship between the structure of the community and toluene consumption exists. A stabilized denitrifying sludge without previous exposition to hydrocarbons was used as inoculum. The work was divided into three parts. At first, in order to examine the effect of acetate on toluene mineralization, an upflow anaerobic sludge blanket (UASB) reactor in steady state was set up. Initially, the reactor was fed with a carbon loading rate of 250 mg acetate- C/l-d as electron source. Nitrate loading rate (mg NO3 - -N /l-d) was adjusted to obtain a constant C/N ratio of 1.4. Later, acetate-C loading rate (mg acetate-C/l-d) was gradually substituted by toluene-C at five toluene-C loading rates (TLR, mg toluene-C/l-d), 25, 50, 75, 100 and 125. Total carbon loading rate and C/N were maintained constant at 250 mg C/l-d and 1.4, respectively. In the second part, continuous and batch cultures were carried out. In continuous assays, an UASB reactor was fed with different carbon loading rates (mg C/l-d) of acetate- C/toluene-C: 100/0, 75/25, 50/50 and 0/100. In these assays, the analysis of the dynamics of denitrifying community profile by DGGE, was studied. In batch assays, different acetate-C/toluene-C ratios (10/70, 30/50, 50/30 and 65/20 mg C/l), were evaluated. Assays with only toluene (mg C/l: 20, 30, 50 and 70) were done as control. In the third part, the oxidation of 15 mg of toluene-C/l in presence or absence of 90 mg of acetate-C/l was evaluated in batch culture. In these assays the number of bssA and 16S rDNA gene copies were quantified using real time quantitative PCR analysis. The results found in the first part showed that when acetate-C was the only electron source a dissimilative denitrifying process resulted as indicated by bicarbonate yield (YHCO3, mg HCO3 - produced/mg carbon consumed) of 0.74 0.005 and denitrifying yield (YN2, mg N2 produced/mg NO3 --N consumed) of 0.89 0.042. The addition of different TLR did not affect the biological process as consumption carbon efficiency (CCE) values remained up to 95% 3.5 and YHCO3 and YN2 values were higher than 0.71 0.03 and 0.88 0.01, respectively. In the second part it was found that as the acetate loading rate decreased in the culture, the carbon and nitrate consumption efficiency also decreased from 91 to 51% and from 99 to 65%. YHCO3 and YN2 values also decreased from 0.82 to 0.46 and 0.82 to 0.47. The analysis of the dynamics of denitrifying community profile by DGGE indicated that there was no prevalence of a certain microbial population in the assays with different acetate- C/toluene-C ratios. The results in batch assays indicated that the specific consumption rate of toluene (qT) was two times higher at 20 mg toluene-C/l in presence of 65 mg acetate-C/l as compared to assays with 20 mg toluene-C as solely electron source. Therefore, the presence of acetate improved the qT. The results in the third part corroborated that the specific consumption rate of toluene improved in the presence of acetate. Real time quantitative PCR analysis showed that the highest number of bssA gene copies occurred in presence of toluene, whereas the highest number of 16S rDNA gene copies was observed in assays with acetate. These results suggest that acetate enhanced the bacteria growth leading to an increase in toluene consumption rate. |
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