In some situations, e.g., MW and boiling (Figs. 1 and 2), time hassignificant negative effect; yield decreases as pretreatment duration increases. This is mainly due to sugar degradation at higher temperatures in an acidic environment, which forms furfural and 5-hydroxymethylfurfural (Zheng et al., 2009). As treatment time increased, the accumulation of fermentation inhibitors and the degradation of the hemicellulose increased simultaneously. Among the tested residence times, 15 min for MW and 10 min for boiling are both considered to be effective methods for obtaining a valuable sugar yield. Higher gains in sugars were obtained with HPA pre-treatment regardless of the duration of sample exposure to stem (Fig. 3b). In detail, when the HPA was