Biodegradation Of Crude Oil By Microalgal-bacterial Consortia And Melocular Characterization Of The Consortia

Oil pollution can lead to serious world-wide ecological problems, and make great threat to the environment and human health. There are considerable interests in microbial degradation and detoxification of these pollutants. Currently, there are some problems in traditional bioremediation technology, such as the degrading-bacteria couldn't survival in environment, insufficiency of dissolved oxygen, and so on. In this study, microalgal-bacterial consortia were used for crude oil degradation, with the aim to improve the feasibility of bioremediation technology for oil polluted water.Two non-axenic microalgae (unialgal culture) were isolated from oil-polluted port water, including one filamentous cyanobacteria named GH1 and one green algae named GH2. GH1 was identified as Oscillatoriales and GH2 was indentified as Scenedesmus obliqnus. Both two algae tolerance for oil, and grew well in medium contain 0.1-1% crude oil. Degradation properties of unialgal culture were tested by UV spectrophotometry and results showed the unialgal GH1 showed high oil degradation efficiency, but unialgal GH2 inferior to GH1. Thus, three oil component degrading bacteria were used for artificial consortia construction with GH2. Unialgal GH2 was not suitable for the consortium construction, axenic Scenedesmus obliquus GH2 combined with the bacteria formed an optimal algal-bacterial consortium.Degradation process was analyzed by GC/MS. Consortium of Oscillatoriales GH1 and associated bacteria could eliminate n-alkanes, alkylcycloalkanes and alkylbenzens in 4 days, 5 days and 7 days, respectively. The degradation rates for alkylated naphthalenes, alkylated fluorenes and alkylated phenanthrenes were achieved 98%, 85% and 80% in 7 days, respectively. The orders of degradation were basically follow the regular pattern that the multimethyl tricyclic PAHs are more biorefractory. The artificial consortium (axenic Scenedesmus obliquus GH2- oil component-degrading bacteria) could eliminate n-alkanes and branch- alkanes in 4days and 10days, respectively. Alkylcycloalkanes and alkylbenzens also completely removed in 7days. The degradation rates for alkylated naphthalenes, alkylated fluorenes and alkylated phenanthrenes were achieved 90%, 76% and 70%, respectively. Higher melocular PAHs were degraded with low melocular materials simultaneously by the consortium, and some intermediates were distinct with the known biodegradation pathway.Molecular biology method was used to analyze the mechanism of oil degradation by miocroalgal-bacterial consortium. There were seven kinds of associated bacteria in unialgal GH1, including two Sphingomonas, one Rhizobium, one Aquimonas, one Flavobacteriaceae and two unculturable bacteria. Rhizobium, Aquimonas, and C5 unculturable bacteria were dominating through the degradation process of alkanes, alkylcycloalkanes and alkylbenzens. The massive growth of Sphingomonas and Flavobacteriaceae leads to abundant decrease of high melocular PAHs. In the artificial consortium, microorganisms'population dynamics showed the degradation process closely correlated with the growth of bacterial strains and their metabolic activity: GS3C and GP3A were predominated and responsible for the aliphatic hydrocarbons degradation; the extensive decrease of PAHs leaded to sharp increase of GY2B; the cooperation of GS3C and GY2B cause co-oxidation of alkylbenzenes.