Bioethanol from lignocellulosic materials has a potential to
become an important sustainable fuel in the coming years. It
can substitute fossil fuels needed in the transportation sector
[1], and fuel ethanol is already produced in vast amounts
(74 hm3 in 2009). In summary, almost 90% of all produced fuel
ethanol comes from both Brazil (from sugar cane) and USA
(mainly from corn) [2]. In many countries bioethanol is
a mandatory supplement of gasoline. The market for ethanol
is expected to further increase in the future and more diverse
crops and materials should be found for the security of safe
supply.
Ethanol can be produced from fermentable sugars, e.g.
C6-glucose derived from starch or cellulose from any lignocellulosic
biomass, for example, agricultural waste or forest
residues [3,4].
A major task in lignocellulosic bioethanol is the pretreatment
step, which is necessary to disrupt and open up the tight
lignocellulosic structure of cellulose, hemicelluloses and
lignin, facilitating further conversion into fermentable sugars
[5]. During hydrothermal pretreatment, the lignocellulosic
biomass is fractionated into a water-soluble hemicellulose
fraction and a solid fraction of cellulose and lignin, which is
then accessible for hydrolytic enzymes. Following or simultaneous
with an enzymatic hydrolysis the pretreated substrate