Efficient bio-reduction of 3-nitro phthalic acid using engineered nitroreductase and V2O5

In this study, a potent nitroreductase enzyme was successfully identified and engineered, which was then employed in an efficient and environmentally friendly chemo-bio nitroreduction process to synthesize 3-amino phthalic acid from 3-nitro phthalic acid. The wild-type nitroreductase from Azorhizobium caulinodans ORS 571 (AcNTR) demonstrated robust catalytic activity. Through error-prone PCR mutagenesis, a mutant variant (Q40R/K267R) was generated, which exhibited a 3.1-fold increase in catalytic efficiency. Molecular docking analysis revealed that the mutations at positions R40 and R267 altered the electrostatic properties of the enzyme's surface, modifying the conformation of the active pocket entrance and thereby enhancing catalytic performance. Additionally, when the mutant Q40R/K267R was combined with divanadium pentaoxide (V₂O₅), the accumulation of 3-hydroxyamino phthalic acid during the biotransformation process was effectively prevented. Under optimized reaction conditions, a 90.0 % conversion rate was achieved, transforming 100 g/L of 3-nitro phthalic acid into 3-amino phthalic acid in just 12 h. These findings highlight the significant potential of biocatalytic processes for large-scale synthesis applications.