Valorization of Potato-processing Residues for the Production of Lactic Acid

Every year large amounts of residues accumulate from potato processing. The aim of this study is to develop a process to valorize these residues as feedstock for lactic acid fermentation in a way that is suitable for industrial production. An enzymatic hydrolysate obtained from potato residues (46 % w/w dry mass starch) was used as a substrate in batch and fed-batch fermentations with Lactobacillus casei. Supplementation of yeast extract (3 g L–1) was required to improve productivities. Despite the inhibitory effect exerted by phenolic compounds in the medium, reasonably high lactic acid concentrations (102 g L–1) and yields (92 %) were obtained, with 92 % (L-isomer) optical purity. It was clearly demonstrated that potato residues are suitable as feedstock for large-scale production of technical grade lactic acid and that the developed process is promising for large-scale biorefinery applications.