Polyphenols have become a research target due to their antioxidant, anti-inflammatory and antimicrobial activity. Obtention via extraction from natural sources includes the revalorization of food wastes such as grape pomace (GP) or apple pomace (AP). In this work, GP and AP were submitted to a liquid–solid extraction using different solvents of industrial interest. Process kinetics were studied measuring the total phenolic content (TPC) and antioxidant capacity (AC), while the extraction liquor composition was analyzed employing chromatographic methods. Extraction processes using water-solvent mixtures stood out as the better options, with a particular preference for water 30%–ethanol 70% (v/v) at 90 °C, a mixture that quickly extracts up to 68.46 mg GAE/gds (Gallic Acid Equivalent per gram dry solid) and 122.67 TEAC/gds (TROLOX equivalent antioxidant capacity per gram dry solid) in case of GP, while ethylene water 10%–ethylene glycol 90% (v/v) at 70 °C allows to reach 27.19 mg GAE/gds and 27.45 TEAC/gds, in the case of AP. These extraction processes can be well-described by a second-order kinetic model that includes a solubility-related parameter for the first and fast-washing and two parameters for the slow mass transfer controlled second extraction phase. AP liquors were found to be rich in quercetin with different sugar moieties and GP extracts highlighted flavonols, cinnamic acids, and anthocyanins. Therefore, using identical extraction conditions for AP and GP and a comparative kinetic analysis of TPC and AC results for the first time, we concluded that ethanol/water mixtures are adequate solvents for polyphenols extraction due to their high efficiency and environmentally benign nature.

Fumaric acid is one of the most promising biorefinery platform chemicals, fruit residues being a very suitable raw material for its production in second generation biorefineries. In particular, apple pomace is a plentiful residue from the apple juice industry, with apple being the second largest fruit crop in the world, with a production that increased from 46 to 86 Mtons in the 1994–2021 period. With a global apple juice production of more than 4.5 Mtons, a similar amount of apple pomace is produced yearly. In this work, apple pomace hydrolysate has been obtained by enzymatic hydrolysis and further characterized for its content in sugars, phenolics and nitrogen using different analytic methods, based on HPLC and colorimetric techniques. Previous to the use of this hydrolysate (APH), we studied if the addition of fructose to the usual glucose-rich broth could lead to high fumaric acid yields, titers and productivities. Afterwards, APH fermentation was performed and improved using different nitrogen initial amounts, obtaining production yields (0.32 g_{Fumaric acid}/g_{consumed sugar}) similar to those obtained with synthetic media (0.38 g_{Fumaric acid}/g_{consumed sugar}). Kinetic modelling was employed to evaluate, explain, and understand the experimental values and trends of relevant components in the fermentation broth as functions of the bioprocess time, proposing a suitable reaction scheme and a non-structured, non-segregated kinetic model based on it.

Rosin is a biomass-based chemical raw material employed in multiple industries: paper, polymers, coatings, adhesives, and more, while glycerol production has experienced a notable increment in recent decades due to it being an unavoidable by-product of the biodiesel industry. Rosin polyol esters are of high interest, and a potential route for the valorization of glycerol. In this work, we compare in detail the esterification routes of rosin triglycerides via classical, industrial thermal processes at 260–280 °C and similar processes catalyzed by Irganox 1425, a high-molecular-weight, multifunctional, phenolic, primary antioxidant produced by BASF and usually in rosin processes. Its chemical name is calcium bis(ethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate). To this end, a novel RP-HPLC method provided us with a detailed description of the compositional evolution of the reacting media. These data have been the basis of a non-linear kinetic modeling procedure where we applied non-linear regression and numerical integration algorithms to determine the network of chemical reactions and the kinetic model of the rosin–glycerol esterification process. Furthermore, the comparison of such kinetic models and their parameters allows us to understand the kinetic effect of the addition of the homogeneous catalyst. The effect of Irganox 1425 results in a notable enhancement of the reaction rates, thus allowing for operation at lower temperatures and a reduction in side reactions as decarboxylation.

Real-time monitoring and dynamic kinetic modeling reveal the role of dissolved oxygen in controlling laccase-catalyzed oxidation reactions.

Vine shoot residues represent an abundant lignocellulosic by-product of the wine industry and a promising source of phenolic compounds with potential functional applications. In this work, a biocatalytic strategy combining aqueous citric acid treatment and subsequent laccase-mediated oxidation was developed for the valorization of vine shoot-derived phenolic liquors. The pretreatment was optimized by response surface methodology, and the selected conditions, 190 °C, 75 min, and 0.82% citric acid, yielded a pretreated solid containing 2.9 ± 0.02% hemicellulose, 47.5 ± 0.20% cellulose, and 51.8 ± 1.87% lignin, together with a phenolic-rich liquor containing 27.66 ± 0.39 mg GAE g⁻¹ dry solid. Chemical characterization by UHPLC-timsTOF-MS revealed a complex mixture of phenolic acids, lignin-derived compounds, carbohydrate derivatives, and secondary metabolites. Laccase-catalyzed oxidation was first used as a reactivity assessment step, showing that the phenolic compounds present in the liquor were susceptible to enzymatic transformation. This treatment decreased the total phenolic content, antioxidant capacity, and antimicrobial activity of the liquor. Subsequently, enzymatic oxidation was carried out in the presence of starch, yielding washed starch solids with retained Folin-reactive phenolic content of approximately 4 mg GAE g⁻¹ starch and measurable antioxidant capacity. Overall, this study demonstrates an integrated valorization route in which citric acid-assisted fractionation of vine shoot residues generates phenolic-rich liquors that can be chemically characterized, enzymatically activated, and directly used for starch functionalization, providing a sustainable strategy to convert agro-industrial residues into bio-based functional systems.

Laccase-catalyzed repolymerization of technical lignins is an emerging biocatalytic strategy for upgrading lignin streams into polymeric systems and biomaterial precursors under mild reaction conditions. Lignosulfonates are attractive substrates for enzymatic polymerization due to their high water-solubility; however, their relatively low reactivity can limit their application. In contrast, organosolv lignin typically presents low-molecular weight and high phenolic content, which increase its susceptibility to laccase-mediated oxidation; however, its limited water solubility restricts enzymatic processing. In this work, lignin blending was evaluated as a strategy to modulate laccase-catalyzed polymerization by combining lignosulfonates (LS) with organosolv lignin from vine shoots (LVS). The effect of LVS incorporation on enzymatic oxidation was investigated through oxygen consumption measurements, viscosity evolution, molecular weight analysis and characterization of LS-based films. The presence of LVS modified oxidation kinetics, leading to prolonged oxidative activity, accelerated viscosity development and higher apparent molecular weight fractions at shorter reaction times compared to LS alone. LS-LVS films were produced to evaluate whether blending affected material surface properties. FTIR analysis supported structural changes consistent with oxidative coupling, while water contact angle measurements showed increased surface hydrophobicity in LS/LVS systems. Overall, the results demonstrate that blending lignins with different structural features can modulate enzymatic polymerization and influence the properties of LS films. This work highlights lignin blending as a simple biocatalytic strategy to modulate laccase-catalyzed polymerization and upgrade heterogeneous lignin streams toward lignin-based biomaterials within biorefinery concepts.