Hydrocarbons Biodegradation and Bioflocculation Behavior of Rhodococcus erythropolis
Date Issued
2009
Date
2009
Author(s)
Chang, Wei-Nung
Abstract
Bioremediation is a common method for removal of petroleum hydrocarbon contaminations. In this study, a strain isolated from alkane-degrading mixed culture TN-4 obtained from petroleum contaminated soil was identified as Rhodococcus erythropolis NTU-1. When degrading alkanes, R. erythropolis NTU-1 owned hydrophobic cell surface, tended to flocculate and trapped most residual alkanes in the medium. The separation of oil-bacteria floccules from culture medium facilitated the removal of alkanes and consequently enhanced the efficiency of bioremediation. Therefore, the major purpose of this research was to investigate the issues regarding biodegradability and bioflocculation of the strain NTU-1.n batch cultivation, the biodegradation process was accompanied by the formation of biofloccules with size ranging from 0.1 to 2 cm in diameter. The morphology of biofloccules depended on the cell density and the amount of residual alkanes in culture medium. About 7.8-fold weight of alkanes could be trapped per unit weight of NTU-1. Approximately 95% of 1000 to 3000 ppmv of linear and branched alkanes could be efficiently removed within 40-68 hr with the aid of biofloccules. Therefore, this effective approach could be considered as a promising bioremediation strategy. Noteworthily, NTU-1 could not only degrade alkanes but has the ability to utilize broad range of hydrocarbons including toluene, phenol, benzene, xylene, carbon tetrachloride and other alkanes (C6-C32) as sole carbon source.esults illustrated that NTU-1 could attach to hydrophobic slide in the presence of alkanes, suggesting that NTU-1 might possess a hydrophobic cell surface which is an important driving force in bioflocculation. Besides, production of biosurfactant was observed during the microbial degradation of n-hexadecane with a minimum surface tension value of 60 mN/m, which helps in the adherence of the cells to oil droplets and subsequent biodegradation. When grown on long-chain alkanes, there were at least 11 different major growth-associated fatty acids produced, with carbon chain length ranging from C12 to C24, and cell surface hydrophobicity was enhanced via fatty acids accumulation at the cell surface. The relative amount of these fatty acids was 3-22 folds higher in alkane-grown cell compared to inoculum. In addition, the composition and relative amount of fatty acids depended upon the hydrocarbon chain length and structure supplied as a substrate.
Subjects
biodegradation
flocculation
hexadecane
fatty acid
Type
thesis
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