Research On The Effect And Mechanism Of Berberine On Anaerobic Digestion Of Sludge

Berberine is used to treat a variety of diseases,leading to an increasing demand for berberine,and a large amount of berberine pharmaceutical wastewater is produced.After research,the physicochemical-biological coupling process is the best method to treat berberine wastewater,but berberine is easily adsorbed by sludge and enters the sludge treatment process.Anaerobic digestion is currently one of the main ways to treat sludge.Berberine has broad-spectrum antibiotic properties,which may affect the anaerobic digestion performance of sludge and the changes in antibiotic resistance genes during anaerobic digestion.In this study,the influence of berberine concentration on the anaerobic digestion performance of sludge was investigated through 4 sets of sequential batch anaerobic reactors.The results showed that berberine could promote sludge reduction and increase the dissolution of sludge solid organic matter;500 mg/L berberine could significantly promote the release of ammonia nitrogen and the accumulation of VFAs;20 mg/L berberine slightly promoted methane production,but 500mg/L berberine would severely inhibit cumulative methane production.However,due to the large amount of iron in the sludge,phosphorus was precipitated in the sludge,resulting in extremely low phosphorus content in the supernatant.In the later stage of anaerobic digestion,the effect of berberine concentration on the properties of sludge was studied.The results showed that anaerobic digestion treatment would greatly reduce the sludge EPS,and the reduction of TB-EPS was significantly greater than that of LB-EPS;Compared with protein,humus and polysaccharides in EPS were easier to degrade,but berberine could inhibit the degradation of polysaccharides;The EPS of digested sludge mainly contained tyrosine and tryptophan.The content of TB-EPS was significantly higher than that of LB-EPS.In addition,500 mg/L berberine would significantly increase tyrosine and tryptophan.From the analysis of infrared spectroscopy,it was known that berberine did not change the structure of functional groups on the surface of digested sludge.In the part of influence mechanism,firstly,the influence of berberine concentration on the four stages of anaerobic digestion was studied.The results showed that in the dissolution stage,berberine promoted the dissolution of sludge proteins and polysaccharides,and berberine promoted the release of proteins in TB-EPS.In the hydrolysis stage,berberine would inhibit the hydrolysis of protein.When the concentration of berberine was too high,the system was difficult to recover the ability to hydrolyze proteins;the hydrolysis of polysaccharides was slightly different,only 500 mg/L berberine would significantly inhibit the hydrolysis of polysaccharides,And the system could quickly restore the ability to hydrolyze polysaccharides.In the acidification stage,20 mg/L berberine slightly promoted the production of VFAs,but 500 mg/L berberine could significantly inhibit the production of VFAs.In the methanogenesis stage,20 mg/L berberine could significantly promote the production of methane,but 100 mg/L and above berberine could severely inhibit the process of methane production.In the mechanism research part,the degradation of berberine was also explored.The results showed that activated sludge had a strong adsorption capacity for berberine,which resulted in almost all berberine in the system remaining in the mud phase;the degradation rate of berberine was fast and then slow,and a large amount of berberine could be degraded in a short time,and finally,The degradation rate of berberine could reach more than 98%.Further explore the influence mechanism of berberine through the microbial community.Studies had found that anaerobic digestion would reduce the abundance and diversity of microorganisms,and the addition of berberine would further reduce the abundance and diversity of microorganisms.After anaerobic digestion,the abundance of Firmicutes,Patescibacteria,and Bacteroidetes all increased significantly.Among them,Patescibacteria would be inhibited by 500 mg/L berberine.On the contrary,Firmicutes and Bacteroidetes could tolerate high concentrations of berberine.pressure.According to genus level analysis,Acetoanaerobium and Petrimonas were two acetogenic functional bacteria,which were in a dominant position in the BH500 group,so the production of VFAs in the BH500 group was higher.The process of methanogenesis involved the participation of many archaea,so the structure of the archaeal community was analyzed.The results showed that hydrotrophic methanogenic archaea,such as Methanobacteria(class level)and Methanobacterium(genus level)can tolerate the pressure of high concentrations of berberine,and therefore dominated the BH500 group.Finally,the effect of berberine on resistance genes(ARGs)during anaerobic digestion was studied through metagenomic data.The results showed that berberine had no effect on the composition and distribution of ARGs with different types of resistance and different resistance mechanisms,but 500 mg/L berberine would slightly increase the abundance of ARGs such as multidrug resistance,tetracyclines and peptides;The ARGs remaining in the digested sludge could develop resistance to 37 antibiotics.Among them,the ARGs with multi-drug resistance were the most numerous,followed by tetracycline resistance genes(TC-ARGs);the main resistance mechanism in the system was antibiotic efflux pump mechanism.Selecting five TC-ARGs for further analysis,it could be found that the vast majority of TC-ARGs were present in bacteria,and a small amount of TC-ARGs would be present in viruses.The main host bacteria of several TC-ARGs were Proteobacteria,Actinobacteria,Chloroflexi,Bacteroidetes and Firmicutes.These types of bacteria phyla were also the dominant microorganisms in the system.100 mg/L berberine increased the proportion of TC-ARGs(except tet X)in Chloroflexi,and 500 mg/L berberine also increased the proportion of TC-ARGs in Firmicutes.