Optimisation of catalytic oxidation conditions for the 2- keto-l-gulonic acid production using response surface methodology

Abstract

L-Ascorbic acid, also known as vitamin C, is a very important antioxidant ingredient situated many usage areas in different industries. 2-keto-L-gulonic acid (2-KLG) is the main precursor component of L-ascorbic acid production and it can be produced from L-sorbose via microbial fermentation or chemical (catalytic) oxidation. While some special strains are used in microbial fermentation, it is benefitted from some catalysts in chemical oxidation. Herein, it was aimed to determine the optimum reaction temperature, pH, and time conditions to produce maximum 2-KLG compound with the catalytic oxidation of L-sorbose in the presence of Pt/Al2O3 catalyst with response surface methodology approach. For this aim, the reaction temperature, pH, and time used as variable factors. The limit values of variable factors were applied as 40–60°C for the temperature, 7.00–9.00 for the pH value, and 3–9 h for the time. The analyses results demonstrated that the increasing temperature and time negatively effected the conversion of L-sorbose into the 2-KLG. The optimum conditions of variable factors were determined as 41.30°C for the temperature, 8.23 for the pH, and 3.25 h for the reaction time by the central composite design. Under these optimum conditions, L-sorbose was converted into 2-KLG with an average yield of 43.70%.