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Liquid hot water (LHW) extraction was used as a pretreatment method to separate the hemicellulose fraction from dried distiller's grain with solubles (DDGS) into liquid phase. Acid hydrolysis using 3.264 % w/w sulfuric acid at 130 °C was performed to convert polysaccharides in LHW extract to monosaccharides. The structure characterization of DDGS in anomeric carbon region based on proton NMR and heteronuclear single quantum coherence (HSQC) during acid hydrolysis was studied in this work. It reveals that the sugar units in DDGS hemicelluloses are constructed with (1-4)-β-D-xylopyranose and α-L-arabinofuranosyl residues. A kinetic model is included to explain the changing concentration of monomer, oligomer, and sugar units. The model was further tested based on the changing concentration of five carbon sugar units during hydrolysis.

Concentrated dilute acid hydrolysate was obtained from hot water extracts of Acer saccharum (sugar maple) and was fermented to ethanol by Pichia stipitis in a 1.3-L-benchtop bioreactor. The conditions under which the highest ethanol yield was achieved were when the air flow rate was set to 100 cm(3) and the agitation rate was set to 150 rpm resulting in an overall mass transfer coefficient (K(L)a) of 0.108 min(-1). A maximum ethanol concentration of 29.7 g/L was achieved after 120 h of fermentation; however, after 90 h of fermentation, the ethanol concentration was only slightly lower at 29.1 g/L with a yield of 0.39 g ethanol per gram of sugar consumed. Using the same air flow rate and adjusting the agitation rate resulted in lower ethanol yields of 0.25 g/g at 50 rpm and 0.30 g/g at 300 rpm. The time it takes to reach the maximum ethanol concentration was also affected by the agitation rate. The ethanol concentration continued to increase even after 130 h of fermentation when the agitation rate was set at 50 rpm, whereas the maximum ethanol concentration was reached after only 68.5 h at 300 rpm.