Optimization Of Media Composition And Study On Soil Remediation By A Highly Efficient Halocarbazole-degrading Strain

Halocarbazole is a new class of pollutants,which has similar toxicity and persistence of dioxin-like compounds,and has been detected in rivers,lakes,oceans,soils and biological samples.At present,The research on various aspects of halocarbazole is still in the early stage.In this paper,the effects of 15 mineral media components on the degradation of 3-bromocarbazole by 3-bromocarbazole degrading bacteria CH-1?Stenotrophomonas sp.?,on the basis of this,the introduction of earthworms synergistically enhances degradation,and new ideas and methods for soil bioremediation were proposed.Plackett-Burman design?PBD?,steepest ascent method?SAM?and central composite design?CCD?using response surface methodology?RSM?were applied to explore the effects of fifteen media components on 3-bromocarbazole degradation by CH-1 was grown on 50 mg·L^-13-bromocarbazole provided as sole substrate in 50 mL mineral media and residual 3-bromocarbazole was quantified after 8 days.The results show that MnCl₂·4H₂O?K?,CuCl₂·2H₂O?F?and CaCl₂?O?are the most significant components,and the optimum concentrations are 15.02,0.022 and 9.14 mg·L^-1,respectively.3-bromocarbazole degradation in the optimized media?79.17±3.25%?closely matched the theoretically predicted value?79.93%?and was nearly 10%higher than that in the unoptimized media.Furthermore,soil biological earthworms were added to the microbial degradation system to explore whether the strain CH-1 and earthworms could synergistically enhance the degradation of 3-bromocarbazole in soil.The results showed that the half-lives of 3-bromocarbazole decreased by 42 days after inoculation with strain CH-1,while the half-lives of 3-bromocarbazole decreased by 7 days after further inoculation with earthworms.Therefore,strain CH-1 can effectively remediate3-bromocarbazole-contaminated soil,and the introduction of earthworms can further improve the efficiency of remediation,both of which have a certain synergistic strengthening effect.This method and ideas have good theoretical and practical significance.