Table 1S presents the analytes that were detected and quantified using HPLC in the substrate hydrolysates after fermentation. Arabinose was detected in most samples and was generally more concentrated in experiments carried out with unwashed substrated. The highest acetic acid concentration was detected when unwashed steam-exploded substrates were used for hydrolysis and fermentation. Under some conditions of pretreatment, the analyte was not detected in the pretreated, washed samples at
0 h of fermentation. Lu et al. (2010) reported that concentrations of 3.3 g/L acetic and 145 mh/L of furfural were considered inhibitory to the fermentation of corn stover pretreated via explosion steam, whereas in the present study, minimal concentrations of these compounds were detected.
Substrate hydrolysates were also analysed by HPLC after fermentation by S. cereviseae CAT-1 using the same method described above for characterizing the pretreatment water solubles (data not shown). Apart from non-fermentable sugars (e.g., xylose and arabi- nose), acetic acid and other organic components that were not utilized by the yeast metabolism, glycerol and xylitol were also detected after fermentation of substrate hydrolysates derived from unwashed and water-washed steam-exploded samples as well as substrate controls (Celuflock and Avicel ). In most cases, the