Screening Of Petroleum Degrading Bacteria In Tropical Seas Of China And Their Application In Bioremediation

Marine oil pollution incidents show an increasing trend year by year.Tropical waters in China are one of the busiest shipping routes for offshore oil transportation in the world,and also the main sea areas for oil and gas resources development in China.The main objective of this paper is to study technologies for remediation of offshore oil pollution adapted to tropical waters in China,in order to cope with potential oil spill accidents in this area.In this paper,the current measures of offshore oil spill treatment are analyzed,and the advantages and disadvantages of physical and chemical methods are listed.Bioremediation technology is the main research direction of this paper because of its economic and environmental friendliness.In this paper,the high-throughput sequencing analysis was carried out on water samples and sediment in the offshore oil hydrocarbon pollution areas in tropical waters,to understand the impact of oil hydrocarbon pollutants on the microbial diversity in the seawater environment,and to master the species characteristics of the dominant flora in the oil pollution environment,so as to provide references for later studies.Then,indigenous oil-hydrocarbon degrading bacteria and surfactant producing bacteria were screened in the seawater environment of tropical waters,in which the latter mainly plays an auxiliary role,and through optimizing the combination,the better oil-hydrocarbon degrading bacteria combination was selected as the main strain material for the later study.Then,the alginate microspheres were used to remove the petroleum hydrocarbon pollutants in the sediment.After the effectiveness was confirmed,the microspheres were modified with the tropical biomass,which enhanced the environmental adaptability of the microspheres.Finally,the unique tropical plant fiber was used as the oil-absorbing material and modified to enhance its hydrophobicity,oil-affinity and floatability,so as to be used as the biological oil-absorbing material for cleaning the thin oil film on the sea surface,and to try to play the dual functions of bacteria fixation and oil-absorbing of the modified fiber.The main results are as follows:1)High-throughput sequencing analysis(bacteria)was carried out for seawater and sediments in two oil-polluted and one non-polluted areas.The diversity of seawater environment in oil-polluted areas was lower than that in non-polluted areas,and the microbial diversity in the sediment environment in the oil-polluted area was much higher than that in the seawater environment.Secondly,through the analysis of dominant bacteria phylum and dominant bacteria genus,the number of dominant bacteria phylum in oil-polluted seawater is lower than that in sediments,but its relative abundance accounts for a larger proportion,while the number of dominant bacteria phylum and dominant bacteria genus in oil-polluted sediments and non-polluted seawater are relatively less,which indicates that the microbial diversity in oil-polluted seawater is significantly affected by petroleum hydrocarbon pollutants.In addition,the main dominant bacteria genera in the oil-polluted area are different among the seawater environment,sediment environment and non-polluted seawater environment,showing the unique structure of microbial community under the influence of petroleum hydrocarbon pollutants.2)The oil-hydrocarbon degrading bacteria sjdq-112,sjdq-13 and sjdq-14 screened from the tropical sea area were identified as Vibrio proteolyticus strain,Vibrio tritonius strain and Bacillus idriensis strain respectively.The optimal degradation strain combination was SJDQ-112:SJDQ-13:SJDQ-14=1:1:2,at pH 7,salinity 35,temperature,the 7d petroleum hydrocarbon degradation rate of the combination was 53.44%,which is better than that of single bacteria,and also adapts to the marine environment in tropical waters.The screened surfactant-producing strain BSM-301 was identified as Micrococcus luteus strain.The test showed that the strain could produce surfactant with petroleum hydrocarbon as carbon source.When combined with the degrading bacteria,the degrading rate of petroleum hydrocarbon of the degrading bacteria combination could be increased by about 20%,which played a good auxiliary effect.3)Traditional alginate microspheres were used to immobilize petroleum hydrocarbon-degrading bacteria and then to remediate petroleum hydrocarbon pollutants.In seawater environment,the 7d degradation rate of petroleum hydrocarbons reached 56.6%and 61.19%in sediment environment.This indicated that the microbial microspheres could be used to remove petroleum hydrocarbon pollutants from offshore sediments.Cassava charcoal,coconut shell charcoal and coconut shell fibers,which are unique biological materials in tropical areas,were used to modify microspheres,which mechanical properties and mass transfer properties were well improved.4)Using banana leaf fiber and coconut shell fiber as oil-absorbing materials,the salt-resistance,acid-alkali-resistance,hydrophobicity,oil-affinity and floatability of the fibers have been greatly improved after modification.The oil-absorbing ratio of the modified banana leaf fiber has increased from 10.16 times to 24.64 times,the coconut shell fiber has increased from 11.68 times to 22.74 times,and under the seawater environment,their primary adsorption rate of oil hydrocarbon is 86.75%and 79.95%respectively.The experiment proves that the modified fibers can be used repeatedly after oil absorption and deoiling.In addition,although the oil hydrocarbon removal rate of the modified fibers after bacterial fixation has not reached the expected dual effect,it has also increased by 19.2%and 13.4%respectively compared with the unfixed bacterial fibers,which could provide technical support for the repair measures after release.In this paper,indigenous petroleum hydrocarbon-degrading bacteria and biosurfactant-producing bacteria are used as strain resources in tropical marine environment of China.After being fixed with petroleum hydrocarbon-degrading bacteria,the modified alginate microspheres are used to clean up petroleum hydrocarbon contaminants in the seabed sediment,and the modified fiber is used forthe end link of offshore oil spill cleaning project,toremove non-recoverable thin oil layers on sea surface.Using the unique biological resources in tropical areas,this paper provides an effective bioremediation technology for removing petroleum hydrocarbon pollutants in tropical waters of China.