1. Introduction
Ethanol is considered as one of the most promising renewable
fuel that can replace fossil fuels-based transportation fuels. It is
most commonly produced by microbial (most often yeast) catalyzed
fermentations using plant biomass as a raw material. Starchy
raw materials (i.e. corn, wheat, sorghum) are still the most common
feedstocks for fuel ethanol production in temperate climate regions
of the world (Europe, North America, Central Asia). However its use
as fuel production resources may affect on the prices of food products
manufactured from them [1]. The use of non-edible parts of the
plant (straws, stalks), known as the lignocellulose biomass, as the
raw material in distillery is nowadays considered as the most promising
opportunity for ethanol production that does not affect the
prices of foodstuffs [2]. However, the conversion of lignocellusosic
biomass into fermentable sugars and, subsequently into ethanol
requires high temperature pretreatment which is often catalyzed
using corrosive, non-ecological or costly agents like acids, alkali,
ionic liquids and others [3]. Moreover the efficiency of saccharification
and fermentation of lignocellulose is still much less efficient in
comparison to starches [4], but starchy raw materials are very
costly and the cost of the feedstock can exceed 65% of the price of
final product [5]. The solution to the problems of affecting food
prices by using agricultural crops for fuel production and the technological
difficulties with conversion of lignocellulosic biomass is
utilization of food industry wastes for production of biofuels. One
of the most promising food waste that can be processed into ethanol
is waste bread. It contains significant amount of starch that is
easily hydrolyzed to monomeric sugars using amylases, the amount
of starch and simple sugars in bread ranges 500–750 and 3–50 g kg1 respectively [6]. Moreover bread contains 100–150 g kg1
of protein which, after hydrolysis to peptides and amino acids, is
essential for yeast growth and accelerated fermentation [7]. Waste
bread is also highly accessible raw material for ethanol processing.
The estimated wastage for bakery products ranges 7–10% of its total