Computer coupled substrate feeding strategies for efficient conversion of D-sorbitol to L-sorbose in fed-batch culture

Abstract

L-sorbose fermentation is of industrial importance since it is an intermediate step in the industrial production of vitamin C. It involves the biological oxidation of D-sorbitol to L-sorbose using Acetobacter suboxydans. Batch sorbose fermentation features substrate inhibition and hence it is impossible to obtain high sorbose productivity in batch bioreactors. Fed-batch fermentations can eliminate substrate inhibition and improve sorbose productivity. Fed-batch sorbose fermentations were conducted using two different nutrient feeding strategies. Fed-batch fermentation conducted by feeding nutrients containing 600 g1 of sorbitol at a constant feed rate of 0.6 l yielded a sorbose productivity of 12.64 g1-h. While fed-batch fermentation conducted by feeding nutrients containing 600 g1 of sorbitol at a linearly decreasing feed rate (0.5–0.041 h) demonstrated a productivity of 17.01 g1 h. The productivity obtained by feeding nutrients at a linearly decreasing feed rate was higher than that obtained by the constant fed-batch fermentation and, therefore, is a better substrate feeding strategy for improving sorbose productivity.