Characteristics and growth kinetics of biomass of Citrobacter freundii strains PYI-2 and Citrobacter portucalensis strain YPI-2 during the biodegradation of Ibuprofen

Ibuprofen (IBU) is the third most commonly used analgesic drug in the world. It enters the water system as a result of human excretion-based wastewater discharges. Hence, it attracts the attention of environmentalists for its ecological fate and degradation behavior. In this study, the two IBU degrading bacterial strains, Citrobacter freundii strain PYI-2 (MT039504) and Citrobacter portucalensis strain YPI-2 (MN744335), were isolated from industrial wastewater samples using an enrichment culture method, identified, and characterized. Physiological and batch culture degradation studies have indicated that these strains involved in IBU degradation and the intermediates produced during the process were analyzed. These strains degrade IBU in the batch culture. The optimum pH was reported for degradation of the PYI2 strain (6.9) and YPI2 strain (5.8), and the optimum temperatures were 42°C and 32°C, respectively. Biomass kinetic analysis of these strains was performed based on physical parameters (temperature, pH, and rpm) and confirmed by the experimental study. As indicated in the GC-MS chromatogram peaks, viz., hydroxyibuprofen, 2-(4-hydroxyphenylpropionic acid), 1,4-hydroquinone, and 2-hydroxy-1,4-quinol various intermediates compounds of degradation pathway were observed. Finally, through the GC-MS data, the metabolic pathway for degradation was predicted. In the study, it was confirmed that Citrobacter freundii strain PYI-2 and Citrobacter portucalensis strain YPI-2 exhibit metabolic potential for the biodegradation of IBU and can be further deployed in bioremediation.