Pre-culture and continuous VHG ethanol fermentation
Pre-cultures in 250 mL shake-flasks and 2.5-L laboratory stirred tank
reactor (KoBioTech, Korea) with a working volume of 1.7 L were cultured
at 30°C and 300 rpm. The pH and aeration rate were controlled at 4.50
(adjusted with 2 mol/L sterilized NaOH) and 0.05 vvm for the bioreactor.
When residual glucose in the pre-culture was below 1.0 g/L, CVEF
operation was initiated at the same conditions as above. The VHG medium
was fed for continuous ethanol fermentation at a dilution rate of 0.027
h-1.