2.5. Ethanol fermentation in a jar fermenter
Batch fermentations were carried out in a 5 l jar fermenter
(Microferm 114, New Brunswick, New Jersey, USA)
with a 3 l working volume, 5% inoculum size and 37 C
incubation temperature. A sugar cane juice medium composed
of the optimal concentrations of sugars, (NH4)2SO4, KH2PO4 and MgSO4 Æ 7H2O, and the optimal pH level, as
determined in the shaking flask experiments was employed.
Four conditions of batch fermentation were studied, i.e.,
(1) agitation at 300 rpm, (2) agitation at 300 rpm with aeration
at 0.2 vvm, (3) agitation at 300 rpm throughout the
fermentation with aeration at 0.2 vvm for the first 12 h
and (4) agitation at 300 rpm with aeration at 0.2 vvm for
the first 12 h, followed by only agitation at 150 rpm. During
the course of fermentation, samples were taken at 4 or
6 h intervals.