A comprehensive review on eco-toxicity and biodegradation of phenolics: Recent progress and future outlook

The profound growth and development of industrial segments discharge enormous quantities of phenolic pollutants into the aquatic environment. Phenolic compounds are priority pollutants and their presence in the water system causes severe hazards to human health and many other living creatures. Thus, the removal of such toxic pollutants has gained a lot of attention in the past few decades. Biodegradation is a sustainable and efficient method for the removal of phenolic pollutants from the aquatic environment. Though microbial degradation of phenolic pollutants is well documented, enzymatic metabolic pathways, co-metabolic biodegradation, the use of sequential bioreactors, and the treatment of real-world industrial wastewater have yet to be adequately addressed. Therefore, the present review focuses on the assessment of biological removal of phenolic pollutants from the contaminated environment along with the various associated problems. In particular, the mechanism of ecotoxicity of phenolic pollutants on the living system, the functional enzymes and metabolic pathways involved in microbial degradation, including co-metabolic and co-culture degradation of phenolic pollutants, were elaborately reviewed. The use of aerobic granular sludge (AGS) in the treatment of recalcitrant wastewater has been addressed. The performances of various bioreactor systems are also compared. The prospects for resource recovery by photosynthetic bacteria that degrade phenolics are also discussed.