Isolation And Identification Of Indole-Degrading Microbe And Its Deodorization Function For Manure

The environmental pollution caused by indolic compounds is increasingly serious.In animal breeding industry,indoles such as skatole?3-methyindole,3MI?derived from anaerobic metabolism of tryptophan are the main components of odor in farms and the main factors causing environmental pollution in farms and their surroundings.How to effectively control indole pollution is a difficult problem for the sustainable development of livestock industry.In this study,culturable bacteria that can utilize 3MI and indole were isolated from poultry feces by enrichment culture method.And their biochemical characteristics,culture conditions,deodorization function and its mechanism were studied on the basis of biochemical and molecular identification,which will lay a foundation for the development of biological deodorization of feed additives.In this study,two strains of bacteria capable of degrading skatole were isolated,and identified as Acinetobacter NTA1-2A?A.toweneri?and Acinetobacter TAT1-6A?A.guillouiae?by evaluating the biochemical characteristics of the isolated strain using Biolog GEN III MicroPlate and sequencing 16S rDNA gene sequencing.The optimal temperature and pH for skatole and indole degrading were determined,and the tolerance to the initial concentration of skatole and indole and the effect of the initial concentration on the degradation effect were evaluated by single factor experiments.The results showed that the strain NTA1-2A and TAT1-6A have optimum temperature and pH value for degrading skatole at 31?and 6 respectively,and they can effectively degrade skatole initial concentration ranging from 65 to 200 mg/L.When the initial concentration was less than200 mg/L,the degradation efficiency of both strains was greater than 85%within 6 days.The degradation rates of supernatants of NTA1-2A and TAT1-6A for the initial concentration of 65 mg/L skatole were 71.46%and 60.71%respectively,in 6 days.The strains NTA1-2A and TAT1-6A degraded skatole in poultry feces by 84.32%and 81.39%,respectively,within 8 days.The strains also were able to degrade indole at the initial concentration of 58.58-300 mg/L.When the initial concentration of indole was less than300 mg/L,the degradation rate of indole was 66.36%?NTA1-2A?,94.87%?TAT1-6A?and96.00%?mixed?within 6 days.The indoles with initial concentration of 120 mg/L could be completely degraded by the supernatant cultured from NTA1-2A and TAT1-6A strains.The indole of 78.67%,83.28%and 83.70%in poultry feces were degraded by NTA1-2A,TAT1-6A and their mixed strains in 8 days.The metabolic mechanism of skatole and indole of two strains was studied by metabonimics analysis of fermentation broth using LC-MS/MS.The results showed that both strains degraded skatole to produce leucine(C₆H₁₃NO₂)and norvaline(C₅H₁₁NO₂),while TAT1-6A could also metabolize skatole to form nitroso-pyrrolidine?C₄H₈N₂O?.Neurine?C₅H1₃NO?and norvaline(C₅H₁₁NO₂)are similar metabolites produced by NTA1-2A and TAT1-6A when indoles are degraded to form indole-5-benzoyl group(C₁₆H₁₀N₂O),dimethyl sulfoxide?C₂H₆OS?,deoxyguanosine(C₁₀H₁₃N₅O₄),leucine(C₆H₁₃NO₂)and n-nitroso pyrrolidine by NTA1-2A and n-nitroso pyrrolidine by NTA1-2A.The metabolites of 3MI and indole produced by the two strains were different from other reports,indicating that the metabolism of indole compounds by different microbial strains was diverse.In conclusion,the strains A.toweneri NTA1-2A and A.guillouiae TAT1-6A screened in this study have strong ability to degrade indoles,and have great application potential in controlling odor in livestock industry,and are also expected to be used in pollution control of indoles and other nitrogenous organic pollutants in chemical industry and other industries.