Fig. 4From: Enhanced 2-keto-l-gulonic acid production by applying l-sorbose-tolerant helper strain in the co-culture systemDetermination of cell density of helper strains in the second screening step. Open bar: the OD of helper strain at 0 h of fermentation; filled bar: the OD of helper strain at 12 h of fermentation under the condition of 15% l-sorboseBack to article page