Efficient production of l-sorbose from d-sorbitol by whole cell immobilization of Gluconobacter oxydans WSH-003

The effect of immobilizing Gluconobacter oxydans WSH-003 on a novel combination carrier material to produce l-sorbose was investigated. A combination carrier of sodium alginate and diatomite was shown to be biocompatible and durable. Our results showed that the carrier material concentration and bead diameter of immobilized cells significantly affected l-sorbose yield. Optimal medium conditions for fermenting l-sorbose were determined to be concentrations of 2.5% (w/v) sodium and 0.5% (w/v) diatomite as well as 2.0-mm bead diameter. Under optimal conditions, fermentation time was 1.3 times lower compared to previous experiments involving free cells. Additionally, the immobilized cells showed excellent stability and were maintained for more than 15 days in a bioreactor. l-sorbose yield was more than 81.0% in the previous nine runs of repeated-batch fermentation. These results indicate that maintaining highly active immobilized cells is feasible for the biosynthesis of l-sorbose.