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