Fungal and bacterial species in degrading carbamazepine: a metabolite perspective: Mini-review

Abstract

Carbamazepine (CBZ) is a ubiquitous pharmaceutical pollutant found in various water environments. This is due to the ineffective CBZ removal, despite employing advanced physiochemical treatment technologies in the current conventional wastewater treatment plants. Thus, bioremediation that utilizes enzymes in microorganisms' systems to bio-mineralize CBZ is suggested as an alternative or complementary technique to remove CBZ more effectively. However, information from published research on the biodegradation of CBZ, the toxicity of metabolites, or toxicity testing was rarely evaluated or assessed cohesively. This aspect is important because if bioremediation of CBZ produces toxic metabolites, it will defeat the main purpose of bioremediation. Thus, the focus of this review is to assess the effectiveness of fungi and bacteria in the biodegradation of CBZ, particularly by looking at the type of enzymes expressed, and the metabolites produced. In this review, information related to the fungal and bacterial species that were reported to degrade CBZ was collated from the published literature and analyzed. Results of the analysis showed that cytochrome P450, laccase, and manganese peroxidase were the common enzymes responsible to degrade CBZ. However, such enzymatic activities can sometimes produce epoxy-CBZ, which is a more toxic compound than the parent compound. Only the fungus Pleurotus ostreatus was able to oxidize epoxy-CBZ via the acridine pathway into acridone, the latter a metabolite that is susceptible to further biodegradation into nontoxic metabolites. However, the identity of the end metabolites is not reported nor characterized. Further, Pseudomonas spp. is the most promising bioremediating agent since it can metabolize CBZ into catechol, the latter can enter the carbon central pathways to generate energy for the bacterial cells.