No special strain, seed culture, inoculation or immobilization of
the saccharomyces cerevisiae was used in this study. A dry baker's
yeast packed in 100 g portion having long durability was immersed
in different amounts into 250 ml Erlenmeyer flasks used a batch
reactor with 100 ml deionized water (DIW). The substrate loading
(CER) was also varied to find optimum yield of ethanol under
different reaction conditions (temperature, fermentation time and
boiling of water with the substrate). Prior to the start of each
experiment, the reactor was purged and blanketed for 2 min by
nitrogen gas for removing air so that the reaction takes place under
anaerobic conditions. A loop trap for venting liberated CO2 during
the reaction was also connected to the reactor. In order to increase
the nutrient transfer between the substrate and yeast cells, a Teflon
magnetic stirrer at 30 rpm throughout the DHF was used and the
temperature was adjusted by a water bath. The liquid phase of the
fermented broth was filtered and placed in vials for analysis of
ethanol concentration. A GC (Agilent 6890) fitted with split inlet
and flame ionization detector (FID) and an HP-FAAP polyethylene
glycol TPA column was used for quantitative analysis of the products.
The oven temperature varied from 70 to 200 C at different
ramps and hold-up times and the carrier gas was helium. Calibration
of the GC was done by pure (99.5%) ethanol with dilute and
different concentrations to be fitted to the different peak areas
obtained for the samples.