Production of Polyhydroxyalkanoates from Waste Grape Must Using Cupriavidus necator DSM 545 and Hydrogenophaga pseudoflava DSM 1034

The valorization of agro-industrial surplus materials or residues is gaining significant attention as a sustainable approach to resource recovery and waste management. Having an excess of grape must can be a common situation in wineries, especially during years of abundant crops. Grape must, the liquid obtained from the pressing of grapes, can be preserved or transformed in various ways to avoid waste but a careful managing could turn the surplus of must into a valuable resource. A possible option could be the use of must as a substrate to obtain high value-added products such as polyhydroxyalkanoates (PHAs). PHAs, biopolymers accumulated by various microorganisms, have attracted considerable interest as alternatives to conventional plastics due to their biodegradability, compostability, and biocompatibility properties. Unfortunately, the PHAs prices are relatively high, mainly for the cost of the substrates used in the production process. The use of cheaper raw materials as substrates for microbial PHAs synthesis are perfect candidate for reducing production costs. This study evaluates the potential of grape must as a substrate for PHAs production by Cupriavidus necator DSM 545 and Hydrogenophaga pseudoflava DSM 1034, two well-known PHAs-accumulating bacteria. A PHAs content of 61.48 % of cell dry weight (CDW), and PHA yield of 4.56 g/L were achieved by C. necator DSM 545 with white grape must. Similar results were obtained with red grape must. H. pseudoflava DSM 1034 reached a polymer accumulation of 67.87% of CDW with a PHAs yield of 5.62 g/L and 63.46% of CDW with a PHAs concentration of 4.73 g/L in red and white grape must respectively. This study highlights the feasibility of using excess grape must as an economical and sustainable substrate for PHAs production, presenting a dual advantage of circular economy and the development of eco-friendly materials.