Preparation of magnetic polyacrylamide hydrogel with chitosan for immobilization of glutamate decarboxylase to produce γ-aminobutyric acid.

Gamma-aminobutyric acid (GABA) is an vital neurotransmitter, and the reaction to obtain GABA through biocatalysis requires coenzymes, which are therefore limited in the production of GABA. In this study, polyacrylamide hydrogels doped with chitosan and waste toner were synthesized for glutamate decarboxylase (GAD) and coenzyme co-immobilization to realize the production of GABA and the recovery of coenzymes. Enzymatic properties of immobilized GAD were discussed. The immobilized enzymes have significantly improved pH and temperature tolerance compared to free enzymes. In terms of reusability, after 10 repeated reuses of the immobilized GAD, the residual enzyme activity of immobilized GAD still retains 100% of the initial enzyme activity, and the immobilized coenzyme can also be kept at about 32%, with better stability and reusability. And under the control of no exogenous pH, immobilized GAD showed good performance in producing GABA. Therefore, in many ways, the new composite hydrogel provides another way for the utilization of waste toner and promises the possibility of industrial production of GABA.

Extraction of camptothecin and 10-hydroxycamptothecin from Camptotheca acuminata fruits by natural deep eutectic solvent.

A natural deep eutectic solvent-based ultrasound-assisted simultaneous extraction (NADES-UAE) of camptothecin (CPT) and 10-hydroxycamptothecin (10-HCPT) was established. The 1.31 mg of CPT and 1.66 mg of 10-HCPT were obtained from each gram of the fruit powder of Camptotheca acuminata under the optimum conditions with a water content of 20%, a liquid-solid ratio of 12 mL/g and an ultrasound time of 20 min. The recovery efficiencies of CPT and 10-HCPT after AB-8 resin enrichment were 70.5% and 74.8%, respectively. The stronger interaction between NADES3 which was screened from 12 kinds of NADES and target components compared with methanol or water was demonstrated using molecular dynamics simulation. Moreover, the recovered NADES3 could be reused at least 4 times. The present research provided an efficient, environment-friendly, and sustainable method for extracting and recovering CPT and 10-HCPT from the fruits of C. acuminata.