Fig. 5

A Strain CGK4 was cultured in LBRC medium in fed-batch fermentation at 30 °C and 350 rpm in a 5-L fermenter under aeration of 1 vvm. B When the titer of acetoin reached 15 g/L, the aeration and rotational speed were adjusted to keep the dissolved oxygen between 0.5–1%. A stock solution comprising 1000 g/L glucose was added when the glucose concentration dropped below 20 g/L to keep the glucose concentration between 20 and 60 g/L