Introduction
The immoderate consumption of non-renewable energy, together with the fact that large urban areas,
has greatly resulted in environmental deterioration and public health problems, has led to find a new
renewable energy [1, 2]. Converting a renewable non-fossil carbon, such as energy crops and
lignocellulosic residues (plants, grasses, fruit wastes and algae) to fuel would assure a continual energy
supply [3]. Lignocellulosic material is the most abundant biopolymer on Earth and its annual production
is estimated at approximately 50 billion tons [4]. Ethanol and hydrogen can be produced by microbial
fermentations from such biomass [5]. However, the economics of biofuel production by fermentation are
significantly influenced by the cost of the raw materials, which accounts for more than half of the
production costs [6]. To achieve a lower production cost, the supply of cheap raw material is thus a