| China is one of the countries that produce and use the most azo dyes in the world.In the production and use of azo dyes,some additives containing inorganic salts will be added,resulting in high salinity of dye wastewater.This requires azo dye decolorizing bacteria with good salt tolerance.However,there are few strains found to be able to exert decolorization performance under high-salt environment,and most of them are only tolerant to sodium chloride,and have poor tolerance to other inorganic salts.Therefore,searching for azo dye decolorizing bacteria with broad-spectrum salt tolerance is of great significance for the popularization and application of azo dye wastewater biological treatment technology.In this study,functional strains capable of decolorizing azo dye cationic blue SD-GSL under hypersaline conditions were screened out,their species were identified,their decolorization performance and influencing factors were analyzed,and their salt tolerance was further determined gene.The research results can provide a scientific basis for the biological decolorization of azo dye wastewater under hypersaline conditions.In this study,a gradient pressure enrichment was used to isolate a strain with high-efficiency decolorization ability for cationic blue SD-GSL under hypersaline conditions from a salt field in Shandong,named YCN-6.According to the 16 S r DNA identification of the physiological and biochemical identification of YCN-6,it was determined to be Halomonas sp..The growth characteristics of Halomonas sp.Under hypersaline environment were studied through growth curves.The decolorization characteristics and influencing factors of Halomonas on the azo dye cationic blue under hypersaline conditions were studied by decolorization curve.Through genome wide sequencing,the genomic characteristics and functional annotation information of the strains are obtained.Using PCR and molecular cloning techniques,nucleic acid sequencing and sequence comparison analysis of the salt-tolerant functional genes of Halomonas sp.The results show that halophilic bacteria can decolor cationic blue efficiently at10% Na Cl concentration,20% Na2SO4 concentration,and 10% Na NO3 concentration,and the final decolorization rate can reach more than 90%.The halophilic bacteria have the best decolorization effect on cationic blue under static conditions,and the optimal inoculation amount is 5%.For the initial concentration of 100~300mg/L,the decolorization rate of cationic blue is all above 90%;after continuous decolorization of cationic blue for 5 times,there is still 85% decolorization rate;All have good decolorization performance.Halophilic bacteria can efficiently decolor cationic blue under the conditions of manganese ion 200 mg/L and copperion 10 mg/L;they have good decolorizing effect on cationic blue,methyl red,methyl orange and chrome black T.The decolorization effect of cationic blue is the best;the experiment of using carbon source shows that halophilic bacteria can effectively decolor the dye when LB,starch,sodium acetate,glucose and lactose are used as the carbon source.The decolorization experiments of live bacteria and dead bacteria and the results of visible ultraviolet spectrum scanning show that the decolorization of dyes by halophilic bacteria is mainly biodegradation;the TOC mineralization rate of dyes before and after decolorization at various salinities reaches more than 70%;YCN-6 decolorization of cationic blue is through the biological action of intracellular and extracellular enzymes.The genome size of halophilic bacteria YCN-6 is 3694820 bp,G + C content is58.21%,and 3492 coding genes are predicted,including 59 t RNA genes and 6 r RNA genes.There are four salt-tolerant functional genes in halophilic bacteria.The bet B gene and ect C gene were amplified and cloned,identified and analyzed.The results showed that the nucleic acid sequence and amino acid sequence of the two genes in the NCBI database and the sequences with higher identity are from Halomonas. |
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