Soybean peroxidase-catalyzed oligomerization of arylamines in water: optimization, kinetics, products and cost. Issue 4 (August 2020)

• Record Type: Journal Article
• Authors: Mukherjee, D.; Taylor, K.E.; Biswas, N.
• Is Part Of: Journal of environmental chemical engineering. Volume 8:Issue 4(2020)
• Publication Date: 2020-08
• Subjects: Enzymatic treatment -- Wastewater -- Arylamines -- Michaelis-Menten model -- Product transformation -- Mass spectrometry; Chemical engineering -- Environmental aspects -- Periodicals; Environmental engineering -- Periodicals; Chemical engineering -- Environmental aspects; Environmental engineering; Periodicals; 660.0286
• DOI: 10.1016/j.jece.2020.103871
• Languages: English
• ISSNs: 2213-2929

Abstract

Highlights: Reaction optimization achieved ≥ 95 % conversion of substrates. Enzymatic reaction of arylamines formed oxidative oligomers and azo-oligomers. Reaction kinetics fitted to Michaelis-Menten model for selected arylamines. Pro-forma cost estimation showed SBP-treatment more economical than conventional. Abstract: Water contamination by refractory and persistent organic aromatic compounds such as poly-substituted mono-cyclic, 4-chloro- o -toluidine and bis-anilino compound, 4, 4′-methylenebis-(2-chlororaniline), is an emerging environmental concern and the compounds are considered priority pollutants by U.S. Environmental Protection Agency. Thus, there is a search for new, efficient and eco-friendly treatment methods for converting and eliminating these pollutants at the point of release. The crude form of soybean seedcoat peroxidase, was able to catalyze the oxidation of these pollutants by generating reactive radicals which couple to form insoluble products. The reaction parameters, p H, hydrogen-peroxide-to- substrate molar ratio and minimum effective enzyme concentration were optimized to achieve ≥95 % removal of these substrates in a 3-h reaction time. The p H optima for 4-chloro- o -toluidine and 4, 4′-methylenebis (2-chlororaniline) were 4.4 and 4.2, respectively. Consumption of H2 O2 of both substrates was near the theoretical stoichiometric value (i.e. H2 O2 /substrate ≤ 1.0). For 95 % removal of 1.0 mM 4-COT and 0.1 mM MOCA, 0.009 and 0.10 U/mL of enzyme were required, respectively. The enzyme kinetic mechanism based on the Michaelis-Menten model was determined for a group of aromatic amines, p -cresidine, 4, 4′-oxydianiline, 4-chloro- o -toluidine and 4, 4′-methylenebis-(2-chlororaniline). The lowest KM was for 4, 4′-methylenebis (2-chlororaniline), 1.70 ± 0.14 μM, indicating highest affinity for the enzyme compared to other amines studied. In addition, product analysis by mass spectrometry revealed presence of "oxidative oligomers" and "oxidized oxidative oligomers" (azo compounds) after the enzymatic treatment. A pro-forma cost estimation emphasized the feasibility of commercialization of the enzymatic treatment, showing it to be 5–8 times lower than conventional methods.