Pretreatment of corn cobs and corn stalks with tetrabutyl phosphate hydroxide ionic liquid to enhance enzymatic hydrolysis process

The abundant lignocellulosic biomass used to produce biofuels was considered the most promising alternative to fossil fuels. In view of this, many studies directly use ionic liquids (ILs) to pretreat lignocellulose for subsequent fermentation. Herein, the strong proton acceptor tetrabutyl phosphorus hydroxide (TBPH) aqueous solution was employed to pretreat corn cobs and corn stalks. The effects of pretreatment time (0.5-2 h), temperature (20-80 degrees C), TBPH aqueous solution concentration (10-40 wt%) and liquid to solid ratio (4 wt/wt-9 wt/wt) on the components and sugar yield were investigated. For the pretreatment of corn cob and corn stalk, the sugar yield was 90.75% and 80.84%, which were about 4 and 4.6 folds of the raw materials (unpretreated corn cob: 22.5% and unpretreated corn stalk: 17.7%). Characterization results confirmed that the lignin and hemicellulose were significantly removed, and the cellulose crystals remained intact. Before and after pretreatment, the two raw materials changed from the initial dense surface morphology to porous and therefore contributed to enhancing the accessibility of cellulose during enzymatic hydrolysis. Furthermore, the sugar yield could still be maintained above 70% after the TBPH aqueous solution was reused 5 times. These results provide guidance for the conversion of other biomass to sugar and further fermentation to prepare the essential products.

Automated summary

The study employed the strong proton acceptor tetrabutyl phosphorus hydroxide (TBPH) aqueous solution to pretreat corn cobs and corn stalks, significantly increasing the sugar yield; removal of lignin and hemicellulose while keeping cellulose crystals intact was confirmed; even after the TBPH aqueous solution was reused 5 times, the sugar yield could still be maintained above 70%.