Efficient and green preparation of baicalein from Radix scutellariae with deep eutectic solvent pretreated bioconversion of cellulose-based microreactor

To enhance the bioconversion ratio, an efficient and green bioconversion method for the preparation of baicalein with a microreactor composed of edible microorganisms ( Aspergillus oryzae and Yeast) treated with deep eutectic solvent co-immobilized on magnetic cellulose was investigated. Various types of deep eutectic solvents (DES) were screened to obtain a superior biocatalytic effect. NADES (CHCL/EG) harvested the maximum catalytic effect at 1.0 wt% under optimal conditions (concentration of bacterium 1.5 x 107 (C x 107cells/mL), wet weight of microreactor 12 g, incubation temperature 33 degrees C and pH 5.0, liquid-solid ratio 30:1 (mL/g), incubation time 48 h), baicalein reached 66.36 mg/g, which increased 3.46-fold to that of normal sample after optimizing. DES could increase the permeability of the cell membrane. The bioconversion rate of baicalin reached 97.2%. Moreover, IC50 values of the extracts measured by the DPPH-radical scavenging test were 0.366 mg/mL (control sample 0.674 mg/mL). The residual activity of the microreactor was 80.2 % after using it 14 times. The experimental results showed that bioconversion is an effective method for preparing baicalein from the plants.