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 and used in many industries. 2-keto-L-gulonic acid (2-KLG) is the main precursor 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, some catalysts are used in chemical oxidation. The aim of this research is to determine the optimum conditions by using the reaction temperature, pH value and time as the variable factors for the production of maximum 2-KLG content with the catalytic oxidation of L-sorbose in the presence of Pt/Al2O3 catalyst with response surface methodology approach. The limit values of variable factors were applied as 40, 50 and 60°C for the temperature; 7, 8 and 9 for the pH value and 3, 6 and 9 h for the time. According to the analyses results, the increasing time and temperature effected the conversion of L-sorbose into the 2-KLG negatively. The optimum conditions as regards the central composite design were determined as 41.30°C for the temperature, 8.23 for the pH and 3.25 h for the reaction time. Under these conditions L-sorbose was converted into 2-KLG with an average yield of 43.70%.