different levels of skim, but the ratio of water-to-solids was not
controlled. The authors suggested that the fermentation rate could
be further increased by adjusting the water-to-solids ratio of the
initial corn–soy slurry because such a ratio was known to affect
the ethanol production rate (Wang et al., 1999). Other parameters,
such as corn particle size, yeast and enzyme doses also affect either
ethanol yield or final ethanol concentration (Naidu et al., 2007;
Rathore et al., 2009).
The stillage obtained from corn–soy co-fermentation should
have an increased lysine content attributable to the high lysine
content in soybean. Together with the high solid and protein contents,
the stillage from the co-fermentation may have significantly
improved feed quality compared to traditional distillers’ dried
grains with soluble (DDGS) (Yao et al., 2011). Thus a complete
compositional analysis of the resulting stillage is needed for future
animal feeding trials.
The objectives of the present study were to determine the effect
of soy skim addition with a fixed ratio of water-to-solids on fermentation
performance in order to provide conclusive evidence
for the beneficial effect of soy protein, and the effects of waterto-
solids ratio, corn particle size, addition of urea, and type of skim
on corn–soy co-fermentation performance, and to present the
composition of the soy-enhanced whole stillage.