Study On Preparation And Degradation Characteristics Of Immobilized Petroleum Hydrocarbon-Degrading Bacteria

Because of a large number of emissions,leakage,oil spills and other oil-related products,petroleum pollution is becoming increasingly source of marine organic pollutants.Immobilization technology has attracted increasing attention owing to its advantages,and has broad applications in the remediation of petroleum hydrocarbons pollution.Therefore,in this study,high-efficiency hydrocarbons-degrading bacteria were screened from long-term petroleum hydrocarbons pollution environment.The mixed bacterial agents were prepared by response optimization method.The modified ramie fibers were used as the carrier to adsorb and immobilize the petroleum-degrading mixed bacterial agents,and the degradation characteristics of the immobilized bacteria were evaluated by simulated bioremediation experiment.The main results are as follows:?1?Based on the biochemical and physiological characteristics and phylogenetic analysis,the four hydrocarbons-degrading bacteria were identified as Acinetobacter calcoaceticus,YQJ-1;Acinetobacter baumannii,YQJ-2;Rhodococcus sp.,YQJ-3 and Acinetobacter venetianus,YQJ-4.The oil degradation rates for YQJ-1,YQJ-2,YQJ-3,and YQJ-4 were49.73%,42.51%,33.77%,and 38.26%,respectively.?2?The strain YQJ-1 with the highest oil degradation rate was explored the petroleum degradation characteristics.The results showed that the strain YQJ-1 had the best petroleum degradation rate at a temperature of 35°C,pH=8,inoculum size of 10 mL,and nitrogen source for yeast soaking.Kinetic analysis indicated that the degradation of crude oil at different initial concentrations by YQJ-1 followed a single first-order kinetics model.And the oil degradation half-life(t_1/2)of 5 g/L crude oil was significantly shorter?4.93d?.Gas chromatography-flame ionization detection?GC-FID?analysis showed that YQJ-1 degraded87.84%of crude oil alkanes?C11-C25?.?3?In order to improve the removal efficiency of petroleum hydrocarbons pollution,Box-Behnken Design was applied to optimize the ratio of mixed bacterial agents under response surface methodology category of Design Expert 8.0 software.The results showed that the best inoculum of the four strains was 2%?YQJ-1?,2%?YQJ-2?,4%?YQJ-3?,and 2%?YQJ-4?,respectively.The optimized mixed bacterial agents exhibited higher petroleum degradation rate of 69.16%.?4?The acetic acid-modified ramie fibers were used as a carrier to adsorb and immobilize the mixed bacterial agents.SEM and FTIR analysis showed that the acetic acid-modified ramie fiber had great hydrophobicity and biocompatibility.The bacteria immobilized on acetic acid-modified ramie fibers degraded 85.16%of petroleum hydrocarbons in artificial sea water after 7 days of incubation.Immobilized bacteria showed better environmental tolerance in different environment.GC-FID showed that the degradation of alkanes by immobilized bacteria was high,especially the degradation rate of short chain alkanes?C12^C20?was as high as 94.85%.?5?In the indoor simulated bioremediation experiment,the degradation characteristics of the immobilized bacteria were evaluated.Analysis of crude oil morphology,pH,dissolved oxygen,dissolved THP content,saturated hydrocarbon content and other evaluation indicators found that the immobilized microbial system has obvious degradation effect on petroleum hydrocarbon.