Valorizzazione di sottoprodotti agr-alimentati con la produzione sostenibilt di poliidrossialcanoati (PHAs) e biocarburanti verdi in ottica di economia circolare

Sustainability has become a defining paradigm in addressing the environmental, social, and economic challenges of the 21st century. Within this framework, the circular economy and bioeconomy represent two complementary models aiming to decouple growth from resource depletion while minimizing waste and emissions. In particular, agri-food systems are at the central of this transition, sustaining human well-being and global economies while also producing large volumes of organic residues. When poorly managed, these residues cause environmental pressures and economic inefficiencies, making their transformation into valuable resources a key strategy for a circular and regenerative bioeconomy. The wine sector illustrates this challenge well. As one of the world’s largest agro-industrial sectors, it produces significant amounts of organic residues, including grape pomace, stems, wastewater, and wine lees, that are often underutilized or discarded. Among these, wine lees represent one of the most abundant and compositionally rich fractions, containing fermentable sugars, phenolic compounds, and microbial biomass. Despite their potential, these residues are still largely destined for distillation or low-value applications, with limited integration into high-value biotechnological processes. This creates both a challenge and an opportunity to embed circularity principles into vitiviniculture. This PhD thesis focuses on the development of innovative strategies for the valorization of Prosecco wine lees from the second fermentation, selected for their abundance, regular availability throughout the year, and relative purity compared to other winemaking residues. Prosecco, being one of the most produced and exported sparkling wines in Northern Italy, ensures a consistent stream of fine lees that can be efficiently recovered and redirected into biotechnological applications. The research focused on the valorization of Prosecco wine lees through three complementary strategies. First, they were employed as substrates for the microbial production of polyhydroxyalkanoates (PHAs), biodegradable and biocompatible bioplastics that can provide a sustainable alternative to fossil-based plastics. At the same time, their potential for renewable energy generation was explored via anaerobic digestion, demonstrating the capacity of lees to be converted into methane and hydrogen and thereby contribute to decarbonization efforts. Finally, wine lees were investigated as a growth medium for beneficial microorganisms to develop microbial inoculants to enhance soil fertility and reduce reliance on chemical fertilizers. In parallel, surplus grape must was also assessed as an additional carbon source for PHAs synthesis, further broadening the range of valorization pathways considered in this study. Overall, this work demonstrates that winemaking residues, particularly Prosecco lees, can be transformed into high-value bio-products and renewable energy, reinforcing the role of circular economy approaches in the agri-food sector. By integrating waste valorization strategies with biotechnological innovation, the thesis contributes to reducing environmental pressures, creating new economic value chains, and promoting a more sustainable and resilient wine industry.