Ball milling promotes saccharification of agricultural biomass by heteropolyacid and enzyme: unlock the lignin cage for sugars recovery

An integrative process for efficient saccharification of hemicellulose and cellulose components from lignocellulosic biomass is of strategic significance for a sustainable society. Raw carbohydrate-lignin matrix demonstrates low reactivity due to existence of crystalline zones and lignin inhibition. To overcome these obstacles, the process synergistically integrating ball milling, heteropolyacid as well as enzymatic hydrolysis, is proposed to unlock the lignin cage for sugars releasing. Among these gathered technologies, ball milling is an alternative pretreatment method for decrystallization of cellulose in bamboo shoot shell (BSS), endowing cellulose I with 71.3% crystallinity index (CrI) to cellulose II with 9.5% CrI accompanying particles decreasing from 283 to 29 μm in D50 size. Under the optimum condition, phosphotungstic acid (HPW) hydrolysis at 150 °C for 2.0 h and subsequently enzymatic hydrolysis at 50 °C for 7.0 h, the results indicate that BSS milled without HPW obtains 763.6 mg/g of monomeric sugars, employing 0.7 g HPW /g substrate while BSS milled with 2.5% HPW can achieve 741.6 mg/g of monomeric sugars but only employing 0.1 g HPW /g substrate in reaction. This integrative strategy provides a good guidance for promoting the conversion of raw lignocellulosic biomass to monosaccharides in high efficiency.