The fractionation of lignocellulose materials, such as olive
stones, into value added products derived from their structural
components has led to the biorefinery concept [3]. When the main
target is the production of fuel-ethanol, the biorefinery scheme is
currently composed of four major unit operations: pretreatment,
hydrolysis of polysaccharides and oligosaccharides, sugars
fermentation to ethanol and, finally, ethanol separation. Pretreatment
is required for initial lignocellulose fractionation and hemicellulose
is usually solubilised in this step [3]. It is also used to
reduce cellulose crystallinity and thereby improve the accessibility
of enzymes to polysaccharide [4]. The choice of pretreatment type
is critical as it influences all subsequent downstream processing
stage and the efficiency of the whole process. With regard to the
chemical pretreatments, liquid hot water (LHW) and dilute sulphuric
acid (DSA) pretreatments are regarded as two of the most
suitable methods for industrial applications and have been studied
for pretreating a wide range of lignocellulosic biomasses [3e6].
Because acid catalyst addition is not needed in LHW pretreatment,
this alternative offers several potential advantages compared to the
dilute acid pretreatment, such as the limited equipment corrosion