High yield production of nanocrystalline cellulose by microwave-assisted dilute-acid pretreatment combined with enzymatic hydrolysis

A dilute-acid pretreatment assisted with microwave irradiation was developed to efficiently fabricate nanocrystalline cellulose (NCC) with the single use of the cellulase from Aspergillus niger. The use of microwave heating and diluted sulfuric acid solution (1, 2, 5, and 10 wt. %) in pretreatment considerably increased the NCC yield of subsequent enzymatic hydrolysis (feedstock to enzyme ratio of 2:1) with a maximum value of 84.4 wt.% from less than 10 wt.% without the pretreatment. The severity of pretreatment conditions affected the crystal dimension of rod-like nanocrystals. The crystallinity and thermal stability of extracted NCC varied by the acid concentration used in pretreatment conditions and also by the duration of enzymatic hydrolysis. The highest peak decomposition temperature of 378.1 degrees C as well as the highest NCC yield were recorded in the NCC extracted in 5 wt.% sulfuric acid with microwave heating. The pretreatment effectively facilitated enzymatic hydrolysis, and the synergetic effect of microwave irradiation in the presence of sulfuric acid was associated with the improved thermal stability and crystallinity in the final products.