Wine Lees as a substrate for the production of polyhydroxyalkanoates (PHAs)

Biomass is a renewable, carbon-neutral resource, and it is the perfect candidate for sustainable production of energy, fuels, materials, and chemical products. Italian wine is one of the most important agro-industrial products of the Mediterranean Area. As reported by the International Organization of Vine and Wine, 4.75 107 hectoliters of wine have been produced in Italy in 2020 and, during the winemaking process, an enormous quantity of by-products and waste is generally produced, with wine lees as the main solid material remaining after alcoholic fermentation. Although several valorization strategies have already been proposed, such as the extraction of antioxidants and the recovery of tartaric acid and ethanol, the production of polyhydroxyalkanoates (PHAs), the so-called “bioplastics”, was never explored. The utilization of such residues as carbon sources could also contribute to the reduction of the PHAs production costs, which strongly depends on the substrate availability and price. The purpose of the present study was to evaluate different bacterial strains, such as Cupriavidus necator DSM 545 and Hydrogenophaga pseudoflava DSM 1034, for their growth and PHAs accumulation in the liquid phase of Prosecco wine lees. Several wine lees pretreatments (ie, autoclave, centrifugation, filtration and/or pH adjustment) were considered and those supporting the highest bacterial growth were identified. In the ameliorated conditions, Cupriavidus necator DSM 545 yielded the highest PHAs content (about 60% of cell dry matter). This study demonstrates the potential of wine lees as a cheap carbon substrate for the PHAs accumulation by Cupriavidus necator DSM 545 and Hydrogenophaga pseudoflava DSM 1034. Further studies are ongoing to improve the biopolymer yields by further optimising substrate treatments, inoculum size as well as media composition and up-scaling the process. These promising results open the way towards effective low-cost PHAs production from wine waste streams.