Unveiling the mechanism of various pretreatments on improving enzymatic hydrolysis efficiency of the giant reed by chromatic analysis

This work sought to understand relation between the variations in chromatic values of biomass during different pretreatments and substrate digestibility. The giant reed (Arundo donax) was subjected to hot water (HW) and dilute acid (DA) aqueous (0.5%, w/w, H2SO4) with elevated temperature. The effects of the pretreatments on the chemical, structure, enzymatic hydrolysis efficiency, and color traits of the giant reed were investigated. Results from the colorimetric system (CIE-L*a*b*) showed that the luminance (∆L*) decreased with temperature for all conditions, and the total color difference (∆E) was dramatically changed during DA pretreatment. The ∆E showed a correlation with the content of the lignin (R2 = 0.76) and xylan (R2 = 0.80). BET (Brunauer-Emmett-Teller) analysis and the images obtained from microscopes confirmed that the porosity of the cell wall increased with the severity of the pretreatments. The 180-DA-pretreated samples exhibited satisfactory enzymatic hydrolysis efficiency with 99.0%. There was a positive correlation between ∆E and enzymatic hydrolysis efficiency, which could serve as rough yet high-throughput judges for predicting the trend of saccharification efficiency of the giant reed.