Winery by-products as potential bioresources for green valorization and sustainable biotechnological applications

Abstract

The wine and distillery industries are among the most prominent sectors in EU agriculture, where 75% of grape production is dedicated to winemaking. The winemaking process generates substantial by-products—more than 30%, including both solid and liquid waste. To address the growing need for effective waste management, green and innovative valorization strategies are essential for transforming these by-products into value-added compounds for sustainable bio-based applications.

This study explores grape marc, along with pre- and post-distillation wine lees, as untapped sources of valuable compounds. The chemical composition of these by-products was analyzed, and the optimization of compound extraction using emerging technologies was investigated. The results indicated that these by-products have dry matter content ranging from 4 to 92 g/100g, low pH (3.4–4.6), and high total acidity (0.33–1.14 g/L). The most abundant source of organic acid in grape marc (GM) is tartaric acid, while pre-distillation (PRE) and post-distillation (POST) wine lees are rich in succinic acid.

Polysaccharide content varied from 83.4 to 16,869.4 mg/L, with GM being particularly abundant in high and medium molecular weight polysaccharides. In contrast, PRE and POST wine lees were more abundant in low molecular weight oligosaccharides. Proteins, measured by the BCA assay, ranged from 6.02 to 55.3 g/L, with PRE exhibiting the highest protein content, followed by POST and GM.

The total polyphenolic content ranged from 3.35 to 88.0 mg gallic acid equivalent per gram. GM was particularly rich in quercetin, while PRE and POST were more abundant in epicatechin and catechin. Additionally, the analysis of PRE and POST in both solid and liquid fractions revealed distinct polyphenolic content, underscoring the varied potential of each by-product.

These winery residues provide valuable source of polysaccharides, proteins, phenolic compounds, and other organic compounds, positioning them as potential bioresources for green valorization. The findings underscore the potential of winery by-products in driving sustainable applications, providing a viable pathway for recovering valuable compounds and advancing a circular, resource-efficient bioeconomy that supports sustainable development.

Acknowledgements

This research was funded by the European Commission, Horizon Europe research and innovation Programme, Marie Skłodowska-Curie Postdoctoral Fellowship, Grant agreement No. 101105437, Project BionovFOOD (Green processing and valorization of organic by-products of distilleries, as novel approaches for climate-smart protein applications for alternative food and circular bio-economy).