Noting that water goes into a gaseous phase at 100°C, hot water pretreatment is a process in which pressure is used to maintain water in a liquid state at high temperatures (140-230°C) as water comes into contact with biomass. The major objective of hot water pretreatment is to wet and solubilize lignocellulosic biomass components especially hemicellulose and make the cellulose component accessible to hydrolytic enzymes. About 40%-60% of the total biomass is solubilized during hot water pretreatment, with 4%-22% of the cellulose, 35%- 60% of lignin, and all of the hemicellulose being removed (Mosier et al. 2005). LHW pre­treatment enhances the cleavage of o-acetyl and uronic acid from hemicellulose to generate acetic, ferulic, glucuronic, and other organic acids, which decreases the pH of lignocellulosic biomass hydrolysates. The structural and chemical changes that occur in lignocellulosic biomass during hot water pretreatment are aided by the presence of these acids in solution. These acids catalyze the formation of monomeric sugars from xylan, arabinan, galactan, mannan polymers as well as aldehydes such as furfural from xylose and 5-HMF from glucose (Ezeji et al. 2007b).