| Malachite green(MG)is a widely used basic triphenylmethane dye.It has been used in textile,printing and pharmaceutical industries.It is also used as a fungicide and preservative in aquatic product breeding and transportation.However,studies have shown that malachite green has carcinogenic,teratogenic,and mutagenic hazards,and it can remain in fish for a long time and be converted into more toxic recessive malachite green,which has direct or potential effects on the human body and the ecological environment.Malachite green is harmful to human life and health.Although it is now banned from being used in aquatic products,it is still being used illegally in some countries and regions due to its low price and high cost performance,causing environmental pollution and indirect damage.Human health is threatened.So far,physical,chemical and biological methods have been used in the restoration and treatment of malachite green pollution.Among them,the biological treatment of malachite green has the advantages of environmental friendliness and good sustainability,and has received widespread attention.Bacterial manganese oxide is an important oxidant and adsorbent.It has been widely used to remove organic pollutants such as bisphenol A and imidazole and micro-pollutants such as heavy metals.However,manganese oxide is easy to oxidize organic pollutants.Produce Mn(II),which will cause secondary pollution to the environment.In recent years,studies have found that the strain P.putida MnB-1 has a synergistic effect when degrading ciprofloxacin,that is,Mn(?)produced when manganese oxide degrades organic pollutants will be oxidized to MnO_x again by manganese oxidizing bacteria,making the bacteria manganese The mixture has the characteristics of strong continuity in the treatment of organic pollutants,so the application prospect is relatively broad.However,there are few reports on the degradation of triphenylmethane dyes or other dyes using bacterial manganese mixtures.Plant endophyte Pantoea eucrina SS01 is an endophytic bacteria isolated from the leaves of Suaeda salsa in the Yellow River Delta wetland by our laboratory.It can oxidize Mn(II)to MnO_x.Strain SS01 has strong manganese oxidation activity.And can promote the formation of manganese film on the surface of the plant host.As an important part of the wetland,wetland plants play an important role in maintaining the ecological stability of the wetland and playing the ecological function of the wetland.On this basis,this experiment used the plant endophyte P.eucrina SS01 as the research object to explore its decolorization activity and decolorization mechanism for malachite green,and found that the bacterial manganese mixture of the bacteria has sustainable degradation and detoxification of malachite green.The activity lays the foundation for the application of bacterial manganese mixture in dye degradation.The main research of this article is as follows:(i)Strain SS01 and its manganese oxide can decolorize malachite green:(1)It was found that strain SS01 can decolorize malachite green.Under the culture conditions of 30?,120 rpm and p H=7.0,the decolorization rate of malachite green(120 mg/L)within 6 hours of the plant endophytes was 67.13%,and the decolorization ability was average.In the continuous decolorization experiment,the ability of plant endophytes to continuously decolor malachite green was weak.The last decolorization rate was 40.91%,and the cumulative decolorization rate was85.23%.(2)The manganese oxide produced by strain SS01 can decolorize malachite green.Under the same decolorization conditions,the manganese oxide of strain SS01 decolorizes malachite green(120 mg/L)to 47.93 mg/L within 6 hours,and the decolorization rate was 60.34%.The continuous decolorization test(100 mg/L/time)shows that the bacteria manganese oxide has the ability to continuously degrade,and the cumulative decolorization rate was 86.59%.It shows that the strain SS01 and its manganese oxide can decolorize malachite green,and the manganese oxide has a certain ability to continuously decolorize.(ii)The bacterial manganese mixture of strain SS01 has a good sustainable decolorization effect on malachite green:(1)In the malachite green decolorization experiment on the bacterial manganese mixture,under the conditions of 30?,120 rpm and p H=7.0,the bacteria the manganese mixture can decolorize malachite green(1000 mg/L)to 38.06 mg/L,the decolorization rate was 96.20%,and the continuous decolorization test(600 mg/L/time)showed that the cumulative decolorization rate of the bacterial manganese mixture was 97.0%,it had a good decolorization effect on malachite green,and found that the bacterial manganese mixture and Mn(II)had a synergistic effect,which can re-oxidize the Mn(II)produced during the decolorization of malachite green to MnO_x.(2)When studying the influence of environmental factors on its decolorization,it was found that the reaction temperature at 60? was the fastest and most thorough reaction temperature,and metal ions generally inhibit decolorization.The study proved that the decolorization ability of the bacterial manganese mixture was stronger and the continuous decolorization effect was better,and there was a synergistic effect in the entire decolorization process.(iii)Degradation mechanism of bacteriomanganese mixture on malachite green:(1)Observing the difference before and after decolorization of bacteriomanganese mixture by TEM,it was found that the flocculent manganese oxide was significantly reduced after decolorization,indicating that manganese oxide was involved in the oxidative degradation of malachite green;Strain SS01 mixed with manganese oxide was weakened by the malachite green poison,indicating that manganese oxide can protect bacteria from toxic substances.(2)Analyze the decolorized product of the bacterial manganese mixture by HPLC-MS,and found several typical malachite green degradation products,such as 4-vinyl-N,N-dimethylaniline,(4-dimethylamino-phenyl)-Phenyl-methanone,etc.,which showed that the bacteriomanganese mixture can degrade malachite green.The degradation products of the bacteriomanganese mixture were analyzed by HPLC-MS,and the possible chemical pathways of the bacteriomanganese mixture were inferred.Therefore,the bacterial manganese mixture can degrade malachite green.(iv)Bacterial manganese mixture had detoxification effect on malachite green:(1)1000 mg/L malachite green can damage soybean radicles and cause soybean taproots to not grow;400 mg/L malachite green and cyanobacteria will be mixed culture.All the cyanobacteria will die;(2)Bacterium manganese mixture had obvious detoxification effect on malachite green.Under the cultivation of bacterial manganese mixture degradation products,the soybean radicle develops normally and the main root develops normally.(3)The degradation products of bacterial manganese mixture are co-cultured with cyanobacteria,and the cyanobacteria grow normally.It showed that the product of malachite green degradation(within the experimental concentration range)by the bacterial manganese mixture was non-toxic and harmless.In summary,this experiment found the degradation of malachite green by the bacterial manganese mixture of strain SS01,and studied the mechanism of the bacterial manganese mixture degrading malachite green,explaining for the first time the chemical pathway of the bacterial manganese mixture degrading malachite green.The toxicity test of soybean and cyanobacteria showed that the degradation products of bacterial manganese mixture had no effect on the growth of soybeans and cyanobacteria,and the degradation products were non-toxic and harmless.The research results have enriched the application of manganese oxide in the degradation of organic pollutants. |
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