A sustainable and Integrated Microbial Biocatalysis of Resveratrol from Polygonum cuspidatum Siebold & Zucc Using Cellulose-Based Immobilised Aspergillus niger with Deep Eutectic Solvent-Assisted Microreactors

An efficient and green method was developed using deep eutectic solvent assistance to enhance the biotransformation method of producing resveratrol from Polygonum cuspidatum Siebold & Zucc, using cellulose-based immobilised Aspergillus niger in the process. Various deep eutectic solvents (DES) were screened to obtain a superior biocatalytic effect. The increase in DES concentration aggravated the degree of cell membrane damage. Natural deep eutectic solvents (NADES) exhibited a more favourable catalytic effect than DES due to their excellent biocompatibility. This enhancement is associated with the hydrogen bonding donor components present in NADES, with catalytic ability ranking as alcohol-based > sugar-based > organic acid. CHCL/EG exhibited the maximum catalytic effect at 1.0 wt%. Under optimal conditions (pH 6.5; temperature, 29.5 °C; ratio of liquid to solid 20:1 (mL/g), and time 47 h), the resveratrol yield reached 32.79 mg/g, which was 13.06-fold to that of the untreated sample (2.51 mg/g). The residual activity of the cellulose-based microreactor was 81.46% after ten trials. The proposed method was successfully employed, demonstrating higher biocatalysis efficiencies and superior environmental protection compared to conventional solvents for resveratrol biocatalysis.