Comparative study of different chemical pretreatments for enhanced enzymatic hydrolysis of sorghum straw

Sorghum straw (SS) is a probable biomass for the synthesis of fermentable sugars. Nevertheless, the saccharification percentage of cellulose in SS is comparatively lower because of the existence of hemicellulose and lignin. The aim of the study was to improve the enzyme-mediated conversion of SS. In the present study, the influence of six diverse pretreatments, namely 2% (w/v) sodium hydroxide (NaOH), 2% (w/v) sulfuric acid (H2SO4), 2% (w/v) sodium carbonate (Na2CO3), 2% (w/v) oxalic acid, 2.15% (w/v) hydrogen peroxide (H2O2) and 95% (v/v) glycerol pretreatment, on the enzymatic digestions was analysed. Among the six pretreatment methods, the maximum cellulose conversion rate (87.7%) was attained with the 2% (w/v) NaOH pretreatment at 121 degrees C. Additionally, the 2% (w/v) NaOH pretreatment demonstrated significant efficiency in lignin removal, whereas the 2% (w/v) H2SO4 pretreatment was effective in hemicellulose removal. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses revealed that most of the crystalline cellulose was hydrolysed during enzymatic saccharification after NaOH-pretreatment. The results of this work suggest that, with NaOH-pretreatment of SS and its efficient enzymatic hydrolysis, the entire process becomes more cost-effective without the use of costly chemicals and commercial enzymes.