| The sulfur in fossil fuels is one of the major sources of air pollution. Hydrodesulfurization (HDS),a chemical method, requires high pressure (1-20 MPa) and high temperature (290-450℃) to reduce the sulfur to hydrogen sulfide.Removing the organic sulphur compounds in oil to a very low level with HDS may lead to a high cost and produce many by-products that are not environmentally friendly.So biocatalytic desulphurisation using microbial cells and their enzymes becomes an attractive alternative because it can be conducted under more gentle conditions at a low sulphur content with a high enzymic specificity.Dibenzothiophene (DBT) was used as a model organic sulphur compound in this paper.After isolation and incubation, a bacteria strain,which can specifically remove sulfur from the model compound of DBT,was selected from various soil and wastewater samples.The desulfurization pathway of EBT-2 was identified to be the 4S pathway (sulphoxide/sulphone/sulphonate/sulphate).According to primary morphological,physiological and chemotaxonomical properties,the strain was identified as Rhodococcus EBT-2.Furthermore, the preliminary study of cell growth kinetics, production kinetic and substrate consumption kinetic was done in this paper. Three kinetic models were developed by theoretical analysis correspondingly. The kinetic parameters under experimental conditions were obtained by use of the least square method for the multivariate linear regression. It is shown from the comparisons between the values calculated by the kinetic models and the measured values that the three kinetic models can well reflect the growth and desulphurisation process of EBT-2.The effects of environmental conditions were investigated in this study.The optimized conditions for both growth and desulfurization of EBT-2 were found as the pH of 7.5,the carbon source of glucose,the nitrogen source of NH4Cl,the temperature of 30℃.In the optimized conditions,0.25 mM DBT was degraded in 72 hours by the growth cell.
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