Reduced coke formation and aromaticity due to chloroperoxidase-catalyzed transformation of asphaltenes from Maya crude oil

► Free-porphyrin asphaltenes from heavy crude oil are catalytically oxidized by chloroperoxidase. ► Fluorescence due to aromatic moieties decreases in treated asphaltenes. ► Forty five percentage of less coke is generated under thermal degradation of enzyme-treated asphaltenes. ► Chemical modification improves the enzyme performance in low water content medium.