Study On Ibuprofen Degradation By Marine Bacteria Under Co-Metabolic Conditions

In recent years,ibuprofen?IBP?,as one of the most widely used non-steroidal anti-inflammatory drugs?NSAIDs?,has become an emerging contaminant and has been widely detected in sewage,surface water,sediments,groundwater and marine environment.It has become a potential threat to human health and the balance of ecosystems.Studies have shown that the conversion behavior of IBP in seawater is different from freshwater.However,current studies are mostly focused on of the distribution and toxicity to marine organisms of IBP in the ocean.Studies on IBP degradation in the ocean only stops with photodegradation,and the biodegradation of IBP in marine environment have not been reported yet.Therefore,studying IBP biodegradation by marine bacteria is of great significance to understand its environmental behavior and fate.First,the properties of IBP co-metabolism by Pseudoalteromonas sp.GCY and Alteromonas macleodii GCW were studied The results showed that GCY and GCW cannot grow with IBP as the sole carbon source,but they can degrade IBP by aerobic co-metabolism.When yeast extract was used as a co-substrate,the two strains had the highest IBP degrading efficiency with 90%and 94%,respectively.When the concentration of co-substrate ranging from 2 to 6 g L^-1,the degradation rate increases with the increase of co-substrate concentration.When the concentration of co-substrate is higher than 6 g L^-1,the degradation rate does not change significantly with the increase of co-substrate concentration.IBP degradation by GCY and GCW followed pseudo-first-order kinetics.The degradation rate constants?k?are 0.071 h^-1 and 0.061 h^-1,respectively,which corresponded to half-live(t_1/2)of33.1 h and 35.4 h.Compared to GCW,GCY has better ability to degrade IBP.The addition of IBP had no obvious effect on the growth curves of GCY and GCW,but it promoted the secretion of EPS and increased the activities of extracellular dehydrogenase and electron transport system.Then,the mechanism of IBP degradation has been primarily discussed.The results showed that the IBP degradation by GCY and GCW was extracellular process and enzyme and reactive oxygen species?ROS?both participated,in which ROS played a major role.The effect of ROS accounted for 85%and 77%in IBP degradation by GCY and GCW,respectively.ROS that can degrade IBP mainly included^·OH,O₂^·-,and H₂O₂.Both GCY and GCW can produce three kinds of extracellular ROS,including^·OH,O₂^·-,and H₂O₂,to degrade IBP.The presence of IBP stimulates activities of enzymes related to extracellular ROS production,including L-amino acid oxidase?LAAOs?and siderophore,thereby promoting IBP degradation.Additionally,five intermediate products were detected during IBP degradation by GCY.It is speculated that the degrading reaction mainly occurred at two substituents of isobutyl and propionate groups.