Selection of a Digitalis purpurea Cell Line with Improved Bioconversion Capacity of Hydroquinone into Arbutin

This study aimed to investigate the biotransformation capabilities of a hydroquinone-tolerant Digitalis purpurea cell line (DpHQ) for bioconverting hydroquinone (HQ) into arbutin, a compound with significant therapeutic and cosmetic applications. The research evaluated the influence of various HQ concentrations, feeding protocols, and carbon sources on arbutin bioconversion yield. By using HPLC-MS for the quantification of arbutin in biomass and medium, the study revealed that higher precursor (HQ) concentration led to a more pronounced growth inhibition under single dosing than sequential dosing. At lower sugar (3%) and precursor (4 mM HQ) levels, arbutin predominantly remained within the cells, whereas higher sugar (6%) and HQ (5-6 mM) levels promoted its release into the medium. Arbutin production ranged from 591 mg/L under single dosing to 3049 mg/L with sequential dosing, with the highest yield being achieved with 5 mM HQ in divided doses and 6% glucose. This study holds novelty for being the first to demonstrate the DpHQ's tolerance to high concentrations of HQ and its efficient capabilities to bioconvert HQ to arbutin, indicating that D. purpurea is equipped with the enzymes required for this process. These aspects highlight its potential as a biotechnological source for arbutin synthesis.