Present study proved that waste wheat-rye bread is a high eth-
anol yielding material in direct conversion to ethanol process using
GSHE resulting in ca. 354 g kgÀ1 of raw material. Moreover applica-
tion of various raw material pretreatment methods (enzymatic
prehydrolysis, sonification and microwave irradiation) further
increased the ethanol yield by ca. 12–35 g kgÀ1. However the stud-
ies were conducted at low raw material loading due to water hold-
ing capacity of bread what resulted in solid-like consistence of the
media at higher loadings. The solution to this seems to be the enzy-
matic prehydrolysis which causes preliminary liquefaction of raw
material.