Investigations of Production of Polyhydroxyalkanoates with Phenol Degradation Using Indigenous Rhizobium and Kinetics of Phenol Degradation
| Autor: | Hsien-Ming Chang, 張先明 |
|---|---|
| Rok vydání: | 2008 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 96 Phenol was often found in industrial waster water. It causes a serious environmental problem because of its toxicity. The process of phenol clean-up usually consumes lot of cost. In this research, we aimed to use microorganism which possesses the ability to degrade phenol and convert simultaneously phenol into biodegradable polymer polyhydroxyalkanoate (PHAs). Base on the above target, two series of indigenous rhizobium Cupriavidus taiwanensis and Burkholderia sp is being used in this study. It is a well known fact that these two species can produce polyhydroxybutyrate (PHB) in our previous studies and presently it is used to examine their ability of phenol degradation. Cupriavidus taiwanensis 187 was the best of these strains. In this research, the optimal fermentation condition for phenol degradation and PHB accumulation is identified as follows, temperature 30oC, agitation 200 rpm and nitrogen source (NH4)2SO4. In the kinetic study, the kinetic parameter of Haldane’s model are = 0.4160 h-1, = 10.87 mg/L and = 341 mg/L.Additionally, mass balance between cell growth and phenol degradation were also dicussed. Before substrate inhibition, YG is 2.9976 g/g; after substrate inhibition, YG is 2.1825 g/g. The modulate simulation by combined kinetic model and mass balance was applied and it was better than simulation by assumed cell yield which was constant in the past. The PHB, produced by Cupriavidus taiwanensis 187 from phenol degradation and through recovery processes was confirmed by GC, 1H-NMR, 13C-NMR and GC-MS analysis. Each result of identifications proved that Cupriavidus taiwanensis 187 was able to use phenol as sole carbon source to produce PHB. From GPC analysis, the mean molecular weight (Mn) of the PHB was 381,423.Fascinatingly, every 500 mg/L of phenol can be converted into 68.5 mg/L PHB via biodegradations by Cupriavidus taiwanensis 187. In the investigation of fermentation strategy, two-stage fermentation strategy can reduce the time of phenol degradation, but is unassisted for PHB accumulation and phenol toleration. For DO-stat fermentation strategy, the concentration of PHB increased by 0.0722 g/L from 0.213 g/L in batch system. It reveals that DO-stat strategy can increase the concentration of PHB. However, the phenol degraded by Cupriavidus taiwanensis 187 contributed mainly cell growth rather than PHB accumulation. And as the times of feeding and culture time increased, the cell yield of substrate and the yield of PHB were down. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
| Externí odkaz: |
|