Lead-removal Mechanism Of Exopolysaccharides Of Athelia Rolfsii

The exopolysaccharides of Athelia rolfsii(AEPS)is an exopolysaccharide obtained by separating and purifying the Athelia rolfsii with corn soak solution as a nitrogen source and corn starch as a carbon source.Documents indicated that EPS showed strong chelating capacity for heavy metal ions and potential antioxidant capacity.AEPS is also safer than chemically synthesized drugs.In order to develop a safe and reliable lead-removal reagent,AEPS produced by fermentation was used as adsorbent to study its chelating capacity to lead ions and its promoting effect on lead-removal in mice as follows:1 The orthogonal test design of AEPS and lead ion adsorption was carried out by single factor test.The orthogonal test results showed that primary fourth-order factors affecting the adsorption were AEPS initial concentration,pH,adsorption time,and adsorption temperature.The results of optimum adsorption conditions were AEPS initial concentration 600 mg/L,pH 8,reaction time 1.5 h,and reaction temperature 35?.Under these conditions,the adsorption rate was 97.85%.The results of adsorption isotherm model showed that AEPS had a good adsorption capacity for lead ions,and the maximum monolayer adsorption capacity was 204.08 mg/g.2 Scanning electron microscopy(SEM)analysis showed after AEPS adsorbed lead ion,the surface structure changed.Fourier-transform infrared spectra(FTIR)analysis showed that —OH and C=O groups were main groups for the reaction between AEPS and lead.And the changes in the fingerprint region also indicated that the structures of AEPS were changed.3 The bio-stability of AEPS-Pb was measured by simulating the gastrointestinal environments.The results showed that AEPS-Pb complex was unstable in the gastric environment and stable in the intestinal environment.4 AEPS was used to alleviate the organ damage in lead-exposed mice.Forty-eight Kunming mice(male)were divided into 6 groups randomly: normal control group,model control group,positive control group,low dose group,middle dose group,high dose group.Analysis of body weight growth rates and visceral index revealed that AEPS kept normal body weight growth in lead-exposed mice.Biochemical indicators(T-SOD,CAT,MDA)in serum determined by the kits revealed that AEPS increased the activity of T-SOD in serum of lead-exposed mice.Lead concentration in brain,liver,kidneys,testis and feces was measured by flame atomic absorption.Reduction rate of lead accumulation in the organs was 76.65%(brain),60.42%(liver),78.43%(kidneys)and 56.47%(testis).The data suggested that lots of lead was expelled along with feces.The results proved that AEPS prevented lead accumulation in the organs of lead-exposed mice.Histological evaluation of brain,liver,kidneys and testis also revealed that AEPS significantly alleviated liver and kidney damage caused by lead poisoning and efficiently protected neurons and sperm cells.We hypothesized that AEPS ingested in the mice chelated with the lead in the digestive system,then excreted through feces,and thus represented a promising method of detoxification for lead poisoning.