Upcycling waste apples into platform chemicals: pilot-scale production of lactic and succinic acids.

The conversion of renewable biological resources into value-added products is essential for supporting the transition to a sustainable bioeconomy. This study explores the use of waste apples-a by-product generated in large quantities along the fresh apple supply chain-as feedstock for the production of two industrially relevant platform chemicals: lactic acid (LA) and succinic acid (SA). A screening identified Heyndrickxia coagulans A203 and Actinobacillus succinogenes DSM 22257 as the most suitable strains for LA and SA production from apple mash, the sugar-rich fraction obtained by pressing waste apples (excluding the solid peel and seed residues). A simplified procedure, omitting costly centrifugation and sterilization steps between enzymatic liquefaction and fermentation, was successfully scaled up, resulting in 73.8 g L-1 LA with a yield of 0.91 g g-1 and 36.8 g L-1 SA with a yield of 0.69 g g-1. The results demonstrate the potential of waste apples as a low-cost, effective feedstock for the biotechnological production of high-value platform chemicals, contributing to the valorization of agri-food waste within a sustainable and circular bioeconomy.