In Silico and in Vitro Studies on Biodegradation of Metronidazole by Providencia Vermicola and Characterization of Biodegraded Metabolites

Metronidazole (MNZ) is both an approved antimicrobial agent and a frequent environmental contaminant. This study aimed to evaluate the biodegradation of MNZ by Providencia vermicola (PV) in vitro and in silico and the characterization of degraded metabolites. The biodegradation experiment was carried out using standard methods. Optimization studies were carried out to assess the effects of concentration and nutrient media on degradation efficiency. Characterization of degraded metabolites was done using Fourier transform infrared spectrometry (FT-IR) and Gas chromatography-mass spectrophotometry (GC-MS). Molecular docking of MNZ with laccase, aldehyde dehydrogenase and nitric oxide (NO) reductase enzymes was done. Toxicity of the biodegraded metabolites was evaluated using Saccharomyces cerevisiae conductometric test (SCCT). Results showed that the organism, efficiently degraded MNZ (95.61 %) at optimum conditions of pH 7, 30 ^° C, 10 mg/L MNZ in peptone medium at day 7. FTIR analysis of the degraded MNZ metabolite revealed the removal of specific compounds (methyl and nitro groups). GC-MS analysis of biodegraded MNZ metabolites majorly revealed benzoic acid methyl ester with m/z 140 and base peak 105. MNZ gave docking scores of ∆G = -5.5 kcal/mol, -5.5 kcal/mol and -5.7 kcal/mol with laccase, aldehyde dehydrogenase and NO reductase enzymes respectively which were higher than the scores of the respective inhibitors of the enzymes. MNZ metabolites were less toxic as revealed by SCCT. PV can be employed in the bioremediation of metronidazole contaminated sites towards a safer environment.