Study On Skatole-degrading Bacteria And The Control Of Fecal Odorous Gas By Compound Bacterium Agent

The malodorous odor is one of the seven major public hazards in the world.It not only causes bad emotions,but is also harmful to the body.So far,most of the research on fecal malodorous gas treatment has focused on the control of NH₃ and H₂S,and only a few have paid attention to other malodorous components.The composition of malodorous odors is very complex and often consists of a variety of malodorous gases.The skatole in feces has a very low odor threshold and can produce a strong malodor when the chemical concentration is very low.Therefore,many literature reports that skatole is one of the main odor substances in human feces.In this study,skatole-degrading bacteria were screened,the degradation conditions were optimized,and the skatole metabolites were determined by liquid chromatography-mass spectrometry(LC-MS).Combine skatole-degrading bacteria and strains that degrade NH₃ and H₂S into a composite deodorant,and compare the deodorizing effects of the composite deodorant on fresh human feces and old human feces.The content changes of skatole,NH₃,H₂S and volatile organic compounds in the deodorization process were measured by liquid chromatography,specific sensors and gas chromatography,and analyzed the changes of microbial diversity.The main findings are as follows:(1)Using septic tank feces as raw materials,the strains capable of degrading skatole were screened simultaneously under both aerobic and facultative anaerobic conditions.The final screening of aerobic bacteria agent H and facultative anaerobe agent Y can degrade 22.39%and 88.52%of skatole with an initial concentration of 80mg/L within 48 hours.The strain Ya isolated from the bacterial agent Y can completely degrade skatole with a concentration of 80 mg/L within 48 hours.The 16S r DNA identified Ya as Acinetobacter.(2)The degradation conditions of bacterial agent H and bacterial agent Y are optimized.The optimal conditions for bacterial agent H are:temperature of 30?,p H of6,bacterial inoculum of 2%,and salinity of 5‰;and the optimal conditions for bacterial agent Y are:temperature of 33°C,p H of 7,bacterial inoculum of 1%,and salinity of 5‰.Under the optimal conditions,the degradation rates of 80 mg/L skatole for bacteria H and Y were 30.68%and 100%,respectively.(3)The skatole metabolites of bacterial agent H and Y are similar,and 6 possible metabolites of skatole have been determined:1H-Indole-3-carboxaldehyde,Indole-3-carboxylicacid,3-Methyloxindole,1H-Indole-2,3-dione,3-Methylindolepyruvate,Pindolol.(4)The initial malodorous odor of the fresh feces group was stronger than that of the old feces group,and the composite deodorant had a better control effect on the odor of the old feces group,which could reduce the odor intensity from 4.60 to 2.55;while the odor intensity of the fresh feces group was from 5.00 to 3.78.(5)During the deodorization process,the removal rates of skatole in the old feces group and the fresh feces group were 88.11%and 47.56%,respectively;and the NH₃and H₂S of the two groups reached the lowest concentration at 24 h,but after 24 h,the concentrations of NH₃ and H₂S both increased.The relative content of volatile organic compounds showed that fresh feces contained more organic acids,but the relative content of organic acids was greatly reduced during the deodorization process.(6)During the process of deodorization,the content of Acinetobacter in the old feces group is continuously increasing,which is related to the efficient removal of skatole;the content of Lactobacillus is the highest at 24 h,which is consistent with the concentration of NH₃ and H₂S at the lowest at 24 h.In the fresh feces group,although no significant proliferation of Acinetobacter was observed,the content of Lactobacillus continued to increase,as high as 10.09%.This may be one of the reasons why the fresh feces group can effectively control NH₃ in the later stage.The compound bacterial agent made in this study has obvious deodorizing effect,especially for controlling the malodorous odor of old human feces,and can be used as a source of bacterial agent for septic tank deodorization.However,the frequency of adding deodorant should be determined according to the actual situation to ensure long-term effective deodorization effect.