Selective Oxidation of Glucose-Galactose Syrup to Gluconic and Galactonic Acid

Abstract

The global food industry, inclusive of dairy, is searching for sustainable upgrading of the large volumes of inedible waste they produce. Presented here is the selective oxidation of Greek yoghurt acid-whey derived, glucose-galactose syrup (GGS) to gluconic and galactonic acid. Aldonic acids are marked as high value biproducts with many applications. Our straightforward approach combines efficient catalytic oxidation and simple separations to upgrade a large dairy waste product to higher value products. Under base free conditions, using Au/Al2O3 catalyst 73% & 55% selectivity towards gluconic and galactonic acid respectively under conditions of 2.5 bar O₂ for 24hr at 80^οC with a low Au:GGS ratio of 1:1000. A selective separation method was developed allowing separation of the two epimeric acids based solely on these solubilities with high purity.