Producción de oxigenasas de hidrocarburos por Aspergillus niger por fermentación en estado sólido
Recently, the solid state fermentation (SSF) has been regarded as a big potential process for the development of bioprocesses and products. Among their applications one can find enzyme production that is mainly extracellular. The oxygenases are intracellular enzymes that catalyze reactions in which...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2011 |
| País: | México |
| Institución: | Universidad Autónoma Metropolitana |
| Repositorio: | Repositorio Institucional de la UAM Iztapalapa |
| Idioma: | español |
| OAI Identifier: | oai:bindani.izt.uam.mx:vx021f35z |
| Acceso en línea: | https://doi.org/10.24275/uami.vx021f35z |
| Access Level: | acceso abierto |
| Palabra clave: | info:eu-repo/classification/LEM/Fungi -- Enzymes info:eu-repo/classification/LEM/Enzimas fúngicas info:eu-repo/classification/LEM/Aspergillus info:eu-repo/classification/LEM/Solid-state fermentation info:eu-repo/classification/LEM/Fermentación en estado sólido info:eu-repo/classification/LEM/Oxigenasas info:eu-repo/classification/cti/6 |
| Sumario: | Recently, the solid state fermentation (SSF) has been regarded as a big potential process for the development of bioprocesses and products. Among their applications one can find enzyme production that is mainly extracellular. The oxygenases are intracellular enzymes that catalyze reactions in which oxygen atoms from molecular oxygen are directly incorporated into the substrate to form a new hydroxyl or carbonyl group. There are two kinds of oxygenases, the monooxygenases/hydroxylases that catalyze the insertion of only one of the oxygen atoms and the dioxygenases/hydroxylases that catalyze the insertion of both oxygen atoms. The oxygenases have a crucial role in the metabolism and the biosynthesis. They have been used to eliminate pollutants from air, soil and water. Furthermore, in the last ten years, they have become important for the pharmaceuticals design and the production of specialty chemicals. In this thesis it is presented the study of hexadecane consumption by Aspergillus niger, ATCC 9642, with and without glucose by submerged fermentation (SmF) and by solid state fermentation (SSF). This study was undertaken with the aim of selecting a suitable culture medium to produce biomass with oxygenase activity. Oxygenase activity was evaluated in resting cells and in enzyme extracts of biomass obtained by both fermentation systems. The oxygenase was also characterized in terms of activity, stability and specificity. The carbon sources used in both SmF and SSF were different mixtures of glucose and hexadecane. In most of the experiments the ratio C/N ratio was (12.12), the exception was a SSF test were a C/N (16.24) was used. The results include the kinetic characterization of both fermentation systems. They show that independently of the system, the use of glucose as cosubstrate increases the specific growth rate ( ), the specific substrate consumption rate (qS) and the biomass yield with respect of substrate (YSX), compared with the values obtained with hexadecane as sole carbon source. The increases in these parameters are always larger for FEL. However, not all cases had been consumed hexadecane in FEL, while FES always presented hexadecane consumption and this was significantly higher than for the case of FEL. In both fermentation systems, the mineralization of the substrate consumed is greater when using a mixture of substrates, that when using glucose or hexadecane as sole sources of carbon. The respiratory coefficients in both systems were higher than 1.0 when only glucose was consumed. Their values were very close to the theoretical value when hexadecane was consumed in the presence of glucose. The study of water soluble metabolites during the liquid and solid cultures of A. niger with hexadecane and glucose (50 % C-glu, 50 % C-hxd) showed a rapid consumption of glucose with accumulation of citric acid and fructose in SSF. However, no accumulation of any metabolite was detected in FEL. Cell-free extracts obtained by SSF and SmF were concentrated by dehydration or stored at -20 oC to study the oxygenase stability. It was found that the enzymatic extracts lost about 75% of the initial activity in only 7 days at -20 oC and a similar effect was shown by dehydration. The loss of activity was independent of the fermentation system. The measurements of oxygenase activity at different temperatures yield two peaks of activity at 26 and 35 oC. The activities reported in this test were significantly different with an = 0.05 using a t-student test. The oxygenase produced under SSF have no specificity difference for aliphatic hydrocarbons (linear and non linear). But, it increases for aromatic substrates as the complexity of the ring increases. Oxygenase produced under SmF has no specific pattern of specificity. It has activity with aliphatic as well as with aromatics. Albeit, the activities were significantly different and lower, at least 7-folds, compared to SSF. Key words: oxygenases, solid state fermentation, aromatic hydrocarbons, hexadecane, polyurethane matrix support, Aspergillus niger. |
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