conditions. The reducing sugars concentrations were calculated
using a calibration curve and reading the absorbance of the samples
at 550 nm. The ethanol concentration was determined for all
fractions collected from distillation by the dichromate method
(Williams and Reese, 1950). This chemical oxidation method is
based on the complete oxidation of ethanol by dichromate in the
presence of sulfuric acid with the formation of acetic acid. Dichromate
ðCr2O2
7 Þ is yellowish in color and the reduced chromic product
(Cr+++) is intensely green. A calibration curve was made with
pure ethanol at different concentrations and the absorbance of
the samples was read at 490 nm. The ethanol production was calculated
as the percent (v/v) of ethanol present in the body fraction
per volume of fermentation broth.