Limosilactobacillus Fermentum Relieves Arsenic Toxicity In Procambarus Clarkii By Gut Remediation And The Field Experiment Application

Procambarus clarkii(crayfish)has become one of the most popular freshwater aquatic products among Chinese consumers.Crayfish are at high risk of being contaminated by heavy metals(HMs),because they can survive in a variety of polluted water environments.Arsenic(As),ubiquitous and carcinogenic,is easy to accumulate in crayfish tissues and then endangers human health through bioaccumulation along the food chain.Trivalent arsenic(As(?))is the main species of As in crayfish.The current remediation methods for As pollution mainly include physical-chemical techniques such as oxidation,adsorption,ion exchange,membrane filtration and so on.However,low removal efficiency,high cost and possible secondary pollution remain the obstacles for these technologies.Phytoremediation has been generally accepted for its environmental friendliness.However,it may be less effective considering the vast area of pollution and the long remediation duration required for plant growth.The problem of HMs residues in crayfish still remains with these remediation techniques.Hence,it is urgent to seek the safe,efficient and economical remediation ways for foodborne HMs pollution to protect humans.Gut remediation is the novel solution for foodborne HMs contamination.In this study,Limosilactobacillus fermentum strain GR-3 screened from the traditional fermented food ?Jiangshui" in the northwest of China was used.The antioxidant potential and As(?)adsorption ability of the strain GR-3 were verified in vitro.Then,the protective effect of feed-additive of strain GR-3 against As toxicity for crayfish were evaluated both in the laboratory and field experiment:Firstly,strain GR-3 exhibited robust antioxidant potential with hydroxyl radicals and DPPH(1,1-Diphenyl-2-picrylhydrazyl)free radicals scavenging rate up to 87.63%and 74.51%,respectively.In addition,strain GR-3 performed the strong As(?)tolerance and adsorption capacity,with the removal rate of 50 mg/L As(?)to50.67%.Secondly,in the laboratory,crayfish was used as the animal model to study the protective effect of strain GR-3 against As toxicity in vivo.Strain GR-3 can successfully colonize in the crayfish intestines,and were excreted through feces after adsorbing As(?).As levels declined in tissues(hepatopancreas,abdominal muscles and gills)and increased in feces following strain GR-3.Among them,the As(?)content in the hepatopancreas was reduced by 36 ± 2.3%,and the transmission electron microscopy(TEM)image visually represented the reduction of As in the hepatopancreas.Administration with strain GR-3 attenuated As(?)-induced oxidative stress and histology damage,with increased activities of the oxidative stress biomarkers including T-SOD(Total Superoxidase),GSH-Px(Glutathione Peroxidase)and CAT(Catalase),and the reduction of MDA(Malondialdehyde)level.More importantly,Illumina Mi Seq sequencing results showed that strain GR-3 regulated As(?)-induced gut dysbiosis in crayfish by gut remediation.The As toxicity in crayfish were ameliorated with promoting the growth of beneficial bacteria such as Bacteroide and inhibiting conditional pathogen like Vibrio.Lastly,gut remediation technology was firstly applied to the field experiment in this study.Strain GR-3 can still successfully colonize in the crayfish intestines even under the more complex situation in the field.Similar to the laboratory results,strain GR-3 promoted the excretion of As from the feces,reduced As residue in the tissues,and attenuated the oxidative stress and tissue damage caused by As(?)exposure.Additionally,probiotic intervention improved the disease resistance of crayfish,and significantly promoted the growth of individuals at a dose of about 50% for yield promotion.In summary,this research not only provides a new strategy for boosting the production in aquaculture industry,but also lays an important practical foundation for ensuring food safety.