Previous studies dealing with utilization of waste bread into
ethanol reported similar or even lower ethanol yields. Ebrahimi
et al. [11] studied the separate hydrolysis and fermentation of
waste wheat bread at a raw material loading of 350 g kg1. They
obtained overall ethanol yield of 350 g per kilogram of bread dry
matter and the alcohol concentration in the fermentation media
about 100 g L1. Kawa-Rygielska et al. [12] reported that prehydrolysis
of waste wheat-rye bread with Ceremix 6X MG preparation
increase the ethanol yield from mashes at 320 g kg1 waste
wheat-rye bread loading from 352.4 to 366.0 g kg1 in comparison
to control. In present study the ethanol yield from substrate (sugars
in raw material) unit was also very high without high-temperature
liquefaction and separate saccharification, however the raw
material loadings were relatively low so the impact of substrate
and product inhibition on yeast cells was minor. In industrial
application higher raw material loadings would be more profitable
because if the higher ethanol concentration is achieved the less
energy is needed to distill it [33].