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|a δ-Viniferin is a resveratrol dimer that possesses potent antioxidant properties and has attracted attention as an ingredient for cosmetic and nutraceutical products. Enzymatic bioconver-sion and plant callus and cell suspension cultures can be used to produce stilbenes such as resvera-trol and viniferin. Here, δ-viniferin was produced by bioconversion from trans-resveratrol using conditioned medium (CM) of grapevine (Vitis labruscana) callus suspension cultures. The CM con-verted trans-resveratrol to δ-viniferin immediately after addition of hydrogen peroxide (H2O2). Pe-roxidase activity and bioconversion efficiency in CM increased with increasing culture time. Opti-mized δ-viniferin production conditions were determined regarding H2O2 concentration, incubation time, temperature, and pH. Maximum bioconversion efficiency reached 64% under the opti-mized conditions (pH 6.0, 60 °C, 30 min incubation time, 6.8 mM H2O2). In addition, in vitro biocon-version of trans-resveratrol was investigated using CM of different callus suspension cultures, showing that addition of trans-resveratrol and H2O2 to the CM led to production of δ-viniferin via extracellular peroxidase-mediated oxidative coupling of two molecules of trans-resveratrol. We thus propose a simple and low-cost method of δ-viniferin production from trans-resveratrol using CM of plant callus suspension cultures, which may constitute an alternative approach for in vitro bioconversion of valuable molecules. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
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