Laccase mediated electrosynthesis of heliotropin on mango-kernel derived carbon nanosphere composite: A sustainable approach

Abstract

Facile fabrication of enzyme immobilized carbon nanospheres (CNS) based catalysts with high electrical conductivity and catalytic efficiency are of decisive importance for their electrocatalysis. A novel, green and highly efficient synthesis route is reported here for the development of an electrode surface with enhanced electrical conductivity and better catalytic activity for the electrochemical synthesis of heliotropin. The obtained biowaste (mango seed kernels) was pyrolyzed and subjected to acid treatment to form functionalized CNS (f-CNS). The functionalized carbon fiber paper (CFP) electrode was employed as a template for laccase immobilization which was further treated with free laccase resulting in the formation of Lac-fCNS/CFP electrode. The developed electrode exhibited excellent electrooxidation of piperonyl alcohol in the presence of 2,2,6,6-Tetramethyl-1-piperidinyloxy (TEMPO), which served as a mediator. A high yield (78%) of heliotropin was achieved during the electrooxidation at 0.78 V via bulk electrolysis. The obtained product (heliotropin aka piperonal) was confirmed via 1H NMR and 13C NMR. Additionally, computational molecular docking analysis of f-CNS:laccase composite showed strong binding affinity (−6.2 kcal/mol) with TEMPO in comparison with free laccase (−5.1 kcal/mol). The excellent selectivity and efficiency of the developed electrocatalyst aim to surpass all other reported laccase-TEMPO mediated based electrocatalytic oxidation reactions.

Keywords

• Mango-seed kernel
• Carbon nanospheres
• Laccase
• TEMPO
• Electrochemical oxidation
• Heliotropin or piperonal