Ethanol-Modified, Supercritical $\text{CO}_2$ Extraction of Persimmon (Diospyros kaki L.) Side Streams for Innovative Bioactive and Antimicrobial Formulations: A Pilot Level Proof-of-Concept and Green Chemistry Evaluation

Abstract

This study addresses the sustainable valorization of persimmon (Diospyros kaki L.) side streams via process intensification through supercritical CO2 technology (Sc-CO2) (35 MPa, 50 °C, 120 min). Namely, the ethanol proportion in the supercritical stream and different levels of operation (LoOP) were tested. In particular, the process at a pilot LoOP (2%-ethanoldoped, 2 kg of sample) enabled the production of a lipophilic extract with enhanced nutritional and biological activity, making it a promising candidate for further research in nutraceutical formulations. More deeply, the extract demonstrated a noted antimicrobial activity against bacteria (Escherichia coli, Bacillus subtilis) and filamentous fungi (Penicillium expansum), with minimum inhibitory concentrations (MIC) ranging from 0.8-7-8 μL/mL that were similar as the benchmark (oregano extract). In addition, the crude displayed a noted Fe content (85.8 mg/100 g extract), with a relevant presence of Mg as well (up to 52% RDI in 100 g extract). The environmental sustainability of the process (pilot level, 2%-ethanol-doped) was assessed through green chemistry metrics. Namely, the protocol displayed 45.9 score in the eco-scale, and a ten-fold reduction for PMI or CEF compared to bench scale experiments (2%-ethanol). Overall, this work highlights the efficiency of an advanced methodology to produce a bioactive extract from persimmon culls that represents a promising candidate for the development of nutraceuticals.