Effects Of Iron And Amino Acids On The Degradation Of Bisphenol F And Bisphenol A By Pseudomonas Sp.ZH-FAD

Bisphenol compounds(BPs)belong to endocrine disruptors,which are of teratogenicityand embryotoxicity.Even at low concentrations,they will still influence biological reproduction and development.Considering the richness and complexity of environmental media,in this paper,BPF was used as a model compound,effects of additional nutrients and iron species on the degradation of BPF by Pseudomonas sp.ZH-FAD were studied,and the influence mechanisms of additional amino acids and iron species were also analyzed.These studies will provide theoretical basis for improving BPs biodegradation.Effects of additional nutrients on the degradation of BPF by Pseudomonas sp.ZH-FAD were studied.The results showed that yeast extract,peptone and casein hydrolysate could promote BPF degradation.Among them,the promoting effect of peptone was the best with91% removal efficiency of BPF.Among the tested amino acids,L-alanine was the most effective,resulting in the removal of 92% BPF.By genome sequencing and gene function annotation of strain ZH-FAD,and the detection of quantitative RT-PCR,it was found that the expression levels of alanine dehydrogenase,alanine racemase and glycine genes in alanine-supplemented system was 2-8.5 times higher than that in alanine-free system at 3.5 h and 5.5 h.Among these enzymes,the relative expression level of alanine dehydrogenase was the highest.These results indicated that the three enzymes were involved in BPF degradation,and alanine dehydrogenase played a major role.The studies showed that the metabolites of the three enzymes are NADH and pyruvic acid.NADH as a co-enzyme factor could improve the degradation rate of BPF by cell extracts of strain ZH-FAD.Pyruvic acid as an important hub of tricarboxylic acid cycle promoted the growth of strain ZH-FAD,resulting in the increase of BPF degradation rate.Effects of additional amino acids and iron species on the degradation of BPF and BPA by strain ZH-FAD were studied.The results showed that amino acid oxidases could catalyze amino acids to produce hydrogen peroxide.Among the tested amino acids,threonine addition resulted in the largest concentration production of hydrogen peroxide(85 μmol/L)in 2 h.Thus,the degradation rate of BPF in threonine-supplemented system was higher than that in alanine-supplemented system in 2 h.Further addition of ferric citrate could promote BPF degradation.The optimal conditions are 1 mmol/L ferric citrate and p H 6.During this process,Fe2+and·OH were detected,indicating that Fenton reaction could occur.Fe S could degradeBPF and BPA.When Fe S was added into strain ZH-FAD-mediated system,BPF degradation rate was higher compared with those in Fe S-supplemented and strain ZH-FAD-mediated systems.Further addition of ferric citrate could promote BPF degradation not only in Fe Ssupplemented system,but also in strain ZH-FAD-mediated system.Thus,ferric citrate addition could significantly improve BPF degradation in Fe S and strain ZH-FADsupplemented system.As strain ZH-FAD could not degrade BPA,BPA degradation rate was lower than that in Fe S-supplemented system when Fe S was added into strain ZH-FAD-mediated system.This result indicated that strain ZH-FAD had an inhibitory effect on BPA degradation.Further addition of ferric citrate could improve BPA degradation rate and cells concentration in Fe S and strain ZH-FAD-mediated system.Compared with Fe S-supplemented system,ferric citrate addition also resulted in the increased inhibition effect of strain ZH-FAD.The above studies showed that suitable amino acids and iron species could promote BPF degradation.