Production of 2-keto-L-gulonic acid using pseudogluconobacter saccharoketogenes with recycling

A method for producing 2-keto-L-gulonic acid which comprises

• (1) culturing a Pseudogluconobacter saccharoketogenes microorganism capable of producing 2-keto-L-gulonic acid from L-sorbose without immobilization, and with another microorganism capable of supplying a growth factor to the Pseudogluconobacter saccharoketogenes, in a liquid culture medium containing L-sorbose as a substrate and producing 2-keto-L-gulonic acid,
• (2) recovering the produced 2-keto-L-gulonic acid, while recovering the microorganism in the culture broth,
• (3) inoculating the recovered microorganism to a new sterilized liquid culture medium comprising L-sorbose, sucrose, ammonium sulfate, and optionally urea, and at least one cell reactivity retention aid selected from the group consisting of yeast extract, dry yeast and corn steep liquor, and,
• (4) repeating the steps (2) and (3) at least once.