Alkaline hydrogen peroxide (AHP) pretreatment of softwood: Enhanced enzymatic hydrolysability at low peroxide loadings

This study investigated the specific effects of hydrogen peroxide (H2O2), alkali and temperature on substrate hydrolysability during alkaline hydrogen peroxide (AHP) pretreatment of Douglas fir. We demonstrated that the presence of a small amount of hydrogen peroxide is essential for effective pretreatment of Douglas fir by alkali. However contradictory to previous finding from others, we found that increasing H2O2 did not directly correlate to enhanced substrate hydrolysability, whereas the alkali charge played a more dominant role. The paper illustrated a strategy to apply AHP for softwood pretreatment with low peroxide loadings and achieve high cellulose-to-glucose yield (up to 95%). It was also found that glucomannan gelation (physicochemical change) occurred during AHP pretreatment of softwood which presents a newly identified recalcitrance factor to substrate hydrolysability. The resulting glucomannan derived hydrogel-like material has a high affinity toward cellulases and can cause a non-productive binding effect.