Yacon (Smallanthus sonchifolius) peel as a promising peroxidase source for the treatment of phenolic wastewater

Abstract

Peroxidases are versatile enzymes that catalyse the oxidation of many inorganic and organic substrates. There are numerous vegetable sources of peroxidases, including the yacon (Smallanthus sonchifolius), an easy-to-grow plant. This study aimed to extract, purify and characterise the peroxidases obtained from yacon roots. We partially purified the enzyme from yacon pell using an aqueous two-phase system (ATPS) and obtained 4.66 purification-fold and 33.87% activity recovery. The enzyme showed an optimal temperature of catalysis 60 °C and optimal pH 11 using pyrogallol as substrate. Considering the oxidation of 2,4-dichlorophenol, these conditions were 37.5 °C and pH 7. Furthermore, the enzyme presented substrate inhibition at high hydrogen peroxide concentrations. The presence of 5 mM Cu2+ inhibited, while and 5 mM Co2+ activated the enzyme. The enzyme remained stable at 50 °C for 60 min and showed improved thermostability compared to horseradish peroxidase. The kinetic mechanism of yacon peroxidase was investigated, and our studies suggested the enzyme follows a Ping-Pong Bi–Bi mechanism. Finally, 2,4-dichlorophenol was selected as a target pollutant, and we obtained as many as 86.26% of bioconversion using yacon peroxidase. The results presented in this article suggest that yacon is a promising source of peroxidase and can be an alternative for bioprocesses applications.