2.4. General fermentation procedure
The liquefaction and simultaneous saccharification and fermentation
were done using the Alcohol Fermentation Monitor (or AFM,
Metrohm Applikon, Netherlands) that could handle six samples at
a time. The total amount of corn slurry was maintained at 400 to
410 g. Ground corn was mixed with cold water or soy skim in a
500-mL AFM glass bottle, and then amylase (0.5 g) was added.
The bottle was connected to the AFM and the mixture was heated
to 76 C (maximum temperature for the instrument) with continuous
stirring at 300 rpm. After 2 h, the bottle was cooled to 30 C
with tap water. The bottle was removed from the AFM to adjust
the pH to 4.7 with 6 mol/L sulfuric acid. Dry yeast (0.5 g), glucoamylase
(0.5 g), lactrol (10 mg), and urea (250 mg) were added. Urea
was added to the fermentation media in most studies except for
those described in Sections 2.7 and 3.3, in which the effect of
nitrogenous nutrient adequacy was examined. The bottle was
tightly connected to the AFM, and the AFM started to monitor
the fermentation by measuring the CO2 flow rate. The CO2 production
rate (mL/min) and total CO2 production (mL) were obtained
from the automated AFM as shown in Fig. 2.
2.4. General fermentation procedureThe liquefaction and simultaneous saccharification and fermentationwere done using the Alcohol Fermentation Monitor (or AFM,Metrohm Applikon, Netherlands) that could handle six samples ata time. The total amount of corn slurry was maintained at 400 to410 g. Ground corn was mixed with cold water or soy skim in a500-mL AFM glass bottle, and then amylase (0.5 g) was added.The bottle was connected to the AFM and the mixture was heatedto 76 C (maximum temperature for the instrument) with continuousstirring at 300 rpm. After 2 h, the bottle was cooled to 30 Cwith tap water. The bottle was removed from the AFM to adjustthe pH to 4.7 with 6 mol/L sulfuric acid. Dry yeast (0.5 g), glucoamylase(0.5 g), lactrol (10 mg), and urea (250 mg) were added. Ureawas added to the fermentation media in most studies except forthose described in Sections 2.7 and 3.3, in which the effect ofnitrogenous nutrient adequacy was examined. The bottle wastightly connected to the AFM, and the AFM started to monitorthe fermentation by measuring the CO2 flow rate. The CO2 productionrate (mL/min) and total CO2 production (mL) were obtainedfrom the automated AFM as shown in Fig. 2.
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