Study On The Effects Of Cofactors On Sulfamethoxazole Biodegradation By Alcaligenes Faecalis

Biodegradtion is a high-effective and environmental friendly approach to remove sulfamethoxazole(SMX).The effects of eight exogenous cofactors,dissolved oxygen and biomass on SMX biodegradation and biotransformation were investigated.The co-culture of Alcaligenes faecalis and Pseudomonas denitrificans that were cultured in the vitamin B12-produced medium were used to remove SMX.The main results were demonstrated as follows:High concentrations of vitamin C,vitamin B6 and GSSG promoted the removal of SMX.High concentraions of vitamin C(100 mg/L),NADH(7.1 mg/L),NAD+(7.1 mg/L)and low concentrations of GSH(0.1 mg/L and 10 mg/L)and vitamin B2(1 mg/L)promoted the transformation from SMX to HO-SMX,while vitamin B12 restrained this process.The low concentrations(0.1 and 10 mg/L)of GSH promoted the growth of A.faecalis.The removal efficiency of SMX related to the biomass activity of A.faecalis.A high removal efficiency was obtained with high biomass activity of A.faecalis.Dissovled oxygen is an important factor that influence the growth of A.faecalis.A.faecalis grew better in high dissolved-oxygen condition than in the low one.Meanwhile,we also discovered that more SMX were degraded in high dissolved-oxygen condition.The deficiency of oxygen inhibited the transformation from SMX to HO-SMX.Pure culture results connot be simply extrapolated to mixed culture conditions.The co-culture of A.faecalis and P.denitrificans had a higher removal efficiency than pure culture of A.faecalis or P.denitrificans in VB12-production medium.Toxic product HO-SMX had not been detected during whole culture period in this condition.What is more,the concentration of SMX had not increased in the late period.In summary,cofactors,especially redox cofactors involved in the metabolism of SMX.It is indicated that cofactors have potential funtions to regulate the process of SMX removal.On the other hand,the biomass activity determined the removal efficiency of SMX,while dissolved oxygen determined the biomass activity of A.faecalis.Consequently,it influenced the removal efficiency of SMX.Hence,the removal efficiency could reach to an ideal level by regulateing dissolved oxygen and biomass properly.Meanwhile,the co-colture of A.faecalis and P.denitrificans had a better performance in removing SMX than the pure culture in new medium.This research provided a new insght to sulfonamides degradation from the perspective of synthetic co-culture.