Production of theabrownins using a crude fungal enzyme concentrate

• A novel enzymatic process is developed for production of theabrownins.
• Enzymes in a microorganism-free system convert tea polyphenols to theabrownins.
• A theabrownins level of 56 g/L was attained in 44 h.
• Theabrownins productivity was nearly 1.3 g/L h.

Theabrownins were produced from infusions of sun-dried green tea leaves using a crude enzyme concentrate of Aspergillus tubingensis TISTR 3647. This fungus had been isolated from a solid state fermentation of Pu-erh type tea. The crude enzyme concentrate contained activities of peroxidase, catechol oxidase and laccase. The enzyme concentrate effectively oxidized the phenolic compounds in green tea infusion to theabrownins. A theabrownins concentration of 56.0 g/L was obtained in 44 h. The reaction mixture contained the green tea infusion and crude enzyme concentrate in the volume ratio of 1: 0.205. The tea infusion had been produced using 200 g of tea leaves per liter of distilled water. The reaction was carried out in a stirred bioreactor at 37 °C with an aeration rate of 1 vvm, an agitation speed of 250 rpm and a controlled pH of 7.0. Peroxidase, catechol oxidase, and laccase acted synergistically to convert the phenolic compounds in green tea infusion to theabrownins. Previously, theabrownins had been produced from green tea infusions only by using live fungal cultures. Production using the microorganism-free enzyme concentrate was comparable to production using the fungus A. tubingensis TISTR 3647. The proposed novel production process using the fungal crude enzymes and green tea infusion, offers a more controlled, reproducible and highly productive option for commercial production of theabrownins.