Sustainable synthesis of catechol compounds using tyrosinase in ethanol cosolvent system

Ethanol is environmentally friendly, not hazardous, and can be produced from renewable sources. In this study, ethanol was applied as a cosolvent for the tyrosinase-catalyzed synthesis of catechol compounds from phenolic compounds, which are abundant in fruit pomace. To investigate the cosolvent function of ethanol on tyrosinase, six types of tyrosinase from Priestia megaterium and water-insoluble phenolic substrates (i.e., phloretin and resveratrol) were used. Biocatalytic activity and stability of tyrosinase were maintained in the ethanol-water system up to 80 % (v/v) ethanol with an optimum of 40 %. The production of catechol compounds using tyrosinase's monophenolase activity was enhanced by optimization of several reaction parameters. Furthermore, the enhanced supply of oxygen to the reaction mixture of tyrosinase by aeration increased the productivity of catechol products. Phloretin and resveratrol were converted to up to 52.5 and 33.7 mM of corresponding catechol products, 3-hydroxyphloretin and piceatannol, with productivities of 7.6 and 4.1 g L^-1 h^-1, respectively, by the optimization of tyrosinase activity and ethanol concentration. Both catechol products are considered bioactive compounds having significant beneficial biological effects on human health. This study is not only applicable to efficient and practical catechol synthesis but also provides a promising method for sustainable and green chemistry.