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 g l −1 of sorbitol at a constant feed rate of 0.6 l h −1 yielded a sorbose productivity of 12.64 g l −1 h −1. While fed-batch fermentation conducted by feeding nutrients containing 600 g l −1 of sorbitol at a linearly decreasing feed rate (0.5–0.04 l h −1) demonstrated a productivity of 17.01 g l −1 h −1. 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.