The authors are thankful for the financial aid provided by “BacchusTech-Integrated Approach for the Valorization of Winemaking Residues” (POCI-01-0247-FEDER-069583), supported by the Competitiveness and Internationalization Operational Program (COMPETE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF). A. Bzainia is grateful to the national funding by the Foundation for Science and Technology (FCT, Portugal) through the PhD grant of UI/BD/153688/2022. R.D. is grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support through national funds FCT/MCTES (PIDDAC) to CIMO (UIDB/00690/2020 and UIDP/ 00690/2020) and SusTEC (LA/P/0007/2020). M.R.C. acknowledges the support by LA/P/0045/2020 (ALiCE), UIDB/50020/ 2020, and UIDP/50020/2020 (LSRE-LCM), funded by national funds through FCT/MCTES (PIDDAC).
The present work focused on the development of a process of sorption-desorption to
purify (E)-resveratrol found in winemaking residues, specifically from the crude extract of
grape stems. The core element of this process is a photo-molecularly imprinted sorbent
(MIS) synthesized by means of the molecular imprinting technique (MIT). This sorbent is a
4-vinylpyridine rich polymer network which binds (E)-resveratrol at stereospecific sites.
Comparison of sorption isotherms of the MIS and its counterpart non-imprinted sorbent
(NIS) shows the higher capability of the MIS to bind (E)-resveratrol. It is noteworthy that
the size of MIS particles was larger than to those of the NIS (as found by scanning electron
microscopy analysis) facilitating its use in sorption-desorption processes without
reaching a high backpressure. The MIS was then used to purify (E)-resveratrol from grape
stems extract in a two-step purification procedure through a simple device. The initial
purification step permitted to increase the purity of (E)-resveratrol from 29% to 78% (34%
of recovery), whereas a further one took it to 87% (70% of recovery). The purified fractions
were obtained in hydroalcoholic medium and contained other bioactive stilbenes such as
(E)-Ɛ-viniferin. The results of this research provide a compelling proof of concept for
room-temperature photopolymerization, enabling the development of highly efficient
imprinted polymers as sorbents for purifying bioactive compounds from agricultural residues.
This significant advancement paves the way for its large-scale implementation in
a circular bioeconomy approach.
