Utilization of wine lees as a substrate for polyhydroxyalkanoates production by employing halophilic and thermophilic bacteria

The increasing demand for sustainable alternatives to petroleum-based plastics has intensified research into polyhydroxyalkanoates (PHAs), biodegradable polyesters produced by microorganisms. Large-scale production remains economically challenging due to the high cost of substrates and the requirement for sterile fermentation conditions. The concept of Next-Generation Industrial Biotechnology suggests employing extremophilic microorganisms that can thrive in harsh conditions and reduce operational costs by minimizing contamination risks. This study explores the use of distilled wine lees, a nutrient-rich by-product of Prosecco winemaking, as a sustainable carbon source for PHAs production by extremophilic microorganisms. Among the 17 thermophilic and 9 halophilic screened strains, Caldimonas thermodepolymerans DSM 15344 exhibited the highest growth and PHAs accumulation on wine lees. Under optimized conditions, this strain achieved a cell dry weight (CDW) of 2.42 g/L and produced 1.17 g/L of poly(3-hydroxybutyrate) (PHB) homopolymer, representing 49.30 % of the CDW. Polymer characterization confirmed physicochemical and thermal properties were comparable to those obtained from standard sugar-based media, such as xylose. In simulated repeated-batch cultivation on DWL, C. thermodepolymerans DSM 15344 maintained stable performance over four subsequent cycles. These results underscore the suitability of C. thermodepolymerans DSM 15344 for cost-effective, sustainable PHAs production from agro-industrial waste and affirm the biotechnological relevance of thermophilic extremophiles in circular bioeconomy strategies.