The initial concentration of reducing sugars and dissolved solids
in the fermentation media was the highest in samples after separate
hydrolysis and fermentation (SHF) pretreatment (Fig. 1a and
b respectively). Enzymatic pretreatment using Ceremix 6X MG
preparation resulted in preliminary hydrolysis and liquefaction of
waste bread giving initial content of sugars and dissolved solidsof ca. 25 and 30 g L1 respectively. Other pretreatment methods
applied (microwave and ultrasonic) did not affected initial concentration
of sugars and dissolved solids at the beginning of the fermentation
in comparison to unpretreated variant. The microwave
and ultrasonic pretreatment did not influenced the content of
non-dissolved solids (ca. 131 g kg1 of media) in comparison to
samples without pretreatment (Fig. 1c). Preliminary hydrolysis of
waste bread with Ceremix 6X MG caused reduction in non-dissolved
particles by ca. 80 g kg1 in comparison to control, microwaved
and sonificated samples, while samples after separate
two-stage hydrolysis with a-amylase, glucoamylase and protease
(SHF) contained the lowest amount of non-dissolved solids among
others (ca. 30 g kg1).