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Projeto de investigação
Molecularly Imprinted Polymers for the Enrichment of Phenolic Compounds from Winemaking residues.
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A simple process to purify (E)-resveratrol from grape stems with a photo-molecularly imprinted sorbent
Publication . Bzainia, Amir; Dias, Rolando; Costa, Mário Rui
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.
Selective fixed-bed fractionation of stilbene subfamilies from grape cane waste using a pyridine-amide adsorbent
Publication . Bzainia, Amir; Keller, Erik; Heeres, André; Costa, Mário Rui P.F.N.; Dias, Rolando
The selective separation of structurally analogous polyphenols from complex plant matrices remains a longstanding challenge in bioseparation engineering. This study introduces a custom-designed adsorbent, poly(2,6-bis(acrylamido)pyridine) (poly(BAAPy)), tailored for subfamily-level resolution of stilbenes obtained from crude grape cane extracts. Leveraging dual amide and pyridine functionalities, poly(BAAPy) achieves selective retention of oligomeric stilbenes (e.g., trans-ε-viniferin, miyabenol C) via multivalent hydrogen bonding and π-π stacking interactions. Comparative breakthrough experiments against commercial poly(4-vinylpyridine) (poly(4VP)) demonstrate superior oligomer retention across both ethanol-water and acetonitrile systems. In dynamic closed-loop adsorption mode, poly(BAAPy) enabled polarity-driven elution and achieved up to a 3.4-fold enrichment of stilbene oligomers, with their recovery in fractions containing ≥ 90 % oligomeric content in a single desorption cycle. Uptake profiles and adsorption selectivity coefficients confirmed poly(BAAPy)’s preference for oligomers under both ethanol-water and acetonitrile conditions. The total stilbene recovery was 75 %. Breakthrough data were fitted using both empirical (Clark, Thomas) and mechanistic models, revealing distinct adsorption dynamics for poly(BAAPy) versus a commercial poly(4VP) resin. This work demonstrates a sustainable valorisation route for grape cane waste, converting viticultural residues into a high-value source of bioactive compounds. The use of green solvents and fixed-bed adsorption aligns with circular economy principles and environmentally conscious separation processes.
Purification of stilbenes from grape stems in a continuous process based on photo-molecularly imprinted adsorbents and hydroalcoholic solvents
Publication . Bzainia, Amir; Igrejas, Getúlio; Pereira, Maria João; Costa, Mário Rui; Dias, Rolando
This study presents a sustainable method to purify stilbenes from residual grape stem biomass. This approach was experimentally validated through the use of a pilot size fixed-bed adsorption prototype for the automation of the purification process. Molecularly imprinted polymers, synthesized through photopolymerization at room temperature and incorporating the 4-vinylpyridine monomer, serve as adsorbents. The purification procedure leads to a significant enrichment, with a more than 22-fold increase in (E)-ε-viniferin and a 9-fold increase in (E)-resveratrol. High recoveries of 80.3% and 62.1% for (E)-ε-viniferin and (E)-resveratrol, respectively, were achieved. Notably, the use of eco-friendly water and ethanol mixtures distinguishes this method from others focused on stilbenes purification. This study further explores the variability of the stilbenes in the residual grape stems by analysing different varieties, emphasizing the complexity of the starting material of the purification process. The range of purities achieved for the fractions enriched with stilbenes (e.g., 12.8% for (E)-ε-viniferin and 3.4% for (E)-resveratrol) are suitable for direct use in controlling of Plasmopara viticola, the agent causing grapevine downy mildew. Furthermore, through compositional combination of these fractions, it is possible to conceive new stilbene-containing phytochemicals with improved anti-fungal activity. Therefore, the developed adsorbents and purification process, enabling the steady enrichment of stilbenes regardless of the unavoidable variability in the initial vine biomass, is a contribution towards the quest for more environmentally friendly and sustainable phytochemicals.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
OE
Número da atribuição
UI/BD/153688/2022