demand because of lack of the starch gelatinization and liquefaction
steps. Also some improvements for direct conversion of starch
to ethanol technology were done. Balcerek and Pielech-Przybylska
[22] studied, among other, the effect of thermal prehydrolysis of
triticale meal using a-amylase and application of protease on the
process of raw starch hydrolysis and fermentation. They discovered
that better efficiency of fermentation was obtained without
thermal activation but with added proteolytic enzyme. Montalbo-
Lomboy et al. [23] studied the effect of sonification of corn
meal slurry prior to direct conversion to ethanol. The results of this
research proved that sonification of raw material improved the
ethanol yield by ca. 20% in comparison to the control samples,
moreover the ethanol yield in sonificated samples was similar to
jet-cooked corn meal. The authors also conducted the economical
evaluation and energy usage for jet-cooking and ultrasonics installations
in industrial environments. They stated that the overall cost
for installation and maintenance for ultrasonic apparatus is lower
in comparison to hydrocooking, also the energy analysis proved
that much less energy is needed for sonification of raw material
than for jet cooking. Also microwave treatment improves enzymatic
hydrolysis of starch [24]. The usage of cheap, waste raw
material like bread leftovers in the cost-effective process of direct
starch hydrolysis and fermentation could be very attractive for ethanol
fuel production. Until now the usage of GSHE for the waste
bread processing into ethanol was not studied. This could be very
effective solution including high ethanol yield and vast reduction
of processing costs in comparison to traditional processes.
The object of this study was to asses the ethanol fermentation
course and efficiency of waste bread using granular starch hydrolyzing
enzyme in comparison to separate hydrolysis and fermentation
process. Also different methods of raw material pretreatment
(enzymatic, ultrasonic and microwave) was conducted to improve
raw starch hydrolysis and fermentation.