Screening And Its Molecular Mechanism Of Salt Tolerance Of Dominant Functional Bacteria In High-salt Medicine Chemical Wastewater

At present,the treatment of high-salt organic wastewater is one of the difficulties and hotspots at home and abroad.In recent years,the successful separation and purification of the dominant functional bacteria such as salt-tolerant halophilic bacteria and aerobic denitrifying bacteria have made it possible to treat high-salt wastewater.Since the adaptation mechanism of salt-tolerant halophilic bacteria to hypertonic environment is still unclear,we need to understand the salt tolerance mechanism of salt-tolerant bacteria,and then transform the strain to obtain a strain that efficiently treats high-salt wastewater.In this study,the activated sludge samples from the sewage treatment plant of Jiangxi Wobangxing Environmental Protection Technology Co.,Ltd.were selected as the research object,and three dominant functional strains with better COD and ammonia nitrogen removal effects were screened out.In the later stage of the study,the transcriptomic analysis of the salt-tolerant yeast was carried out,and the specific salt-tolerant pathways and mechanisms of the strain were studied to find out the relevant salt-tolerant genes.The strain was subjected to ultraviolet-normal pressure room temperature plasma mutagenesis in order to obtain a higher salt-tolerant strain.The results of this study were as follows:1.A high salt-tolerant strain was screened from the activated sludge of the sewage treatment plant of Jiangxi Wobangxing Environmental Protection Technology Co.,Ltd.,The strain was identified as Meyerozyma guilliermondii by morphology and molecular ecology,named W2,the gene bank number is KX447139.The COD removal rate could reach 73% when the strain was applied to sewage treatment.2.An aerobic denitrifying bacteria was screened from the activated sludge,by BTB screening medium.The strain was identified as Paracouccus by morphology and molecular ecology and named LX 1-3,and NCBI Gen Bank accession number of the Paracouccus was MH156598.The strain and the salt-tolerant bacteria(KX447139)co-process sewage,the results show that the denitrification efficiency was remarkable.Under aerobic conditions,the aerobic denitrifying bacteria and salt-tolerant bacteria were putted into the sewage with 1:1 inoculum,after 48 h reaction at 30℃,the ammonia nitrogen removal rate was as high as 86.36%.3.A strain with strong ammonia nitrogen removal ability was screened from activated sludge by modified R2A(enriched)medium.The strain was identified as Aquadcterium olei by morphology and molecular ecology and named XTT,and NCBI Gen Bank accession number was(MH251870).The strain was treated with aerobic denitrifying bacteria together,and the nitrifying bacteria and denitrifying bacteria were inoculated at a ratio of 1:3,after shaking at 28 °C for 72 hours,the ammonia nitrogen removal rate was as high as 95%.4.The transcriptome sequencing of Meyerozyma guilliermondii was carried out by high-throughput sequencing technology.The results showed that 8220 unigenes were obtained from the sequencing data after de novo splicing,among which 6334 genes had annotation information in the swisssprot library.With salt-free as reference,there were 1135 unigenes that differentially expressed under low salt stress,and 1948 unigenes were differentially expressed under high salt stress.With low salt as reference,3056 unigenes were differentially expressed under high salt stress.The metabolism pathways of MAPK signaling pathways were correlated with salt tolerance in the KEGG metabolic pathway database.There were 51 unigenes involved in MAPK signaling pathway,of which 6 genes were significantly differentially expressed.5.Using Meyerozyma guilliermondii W2 as raw material,a high salt-tolerant strain W2U1C1 was obtained after UV-induced mutagenesis for 90 s and atmospheric pressure room temperature plasma for 90 s,and its salinity increased from 18% to 22%.In this paper,three functionally dominant bacteria were obtained by activated sludge screening.After optimization of wastewater treatment,COD removal rate and ammonia nitrogen removal rate were greatly improved.The salt tolerance mechanism of salt-tolerant yeast was studied,and the salt-tolerant pathways and related genes were analyzed.This provides a selection of strains for the treatment of high-salt organic wastewater in the future.