Abstract
Dry chemo-mechanical (DCM) pretreatment is an interesting eco-friendly approach for bioconversion of lignocellulosic biomass into sugars and other valuable molecules. In this study, different dry DCM pretreatments were developed using a combination of alkaline and vibro-milling “VBM”. High-resolution fractional factorial 2k-1 design (FFD) was applied to evaluate statistically the effects of NaOH concentration (2–10%), impregnation ratio (20–50%), milling time (10–60 min), milling frequency (15–30 Hz), and ball diameter (1 or 2.5 cm) on reducing sugars release from chickpea straw (CS). The optimal conditions ensuring the maximum concentration of reducing sugars (374.70 mg/g biomass) after 72 h of enzymatic hydrolysis were 10% of NaOH, impregnation of 50%, 60 min of VBM, frequency VBM of 30 Hz, and ball diameter of 2.5 cm. Furthermore, an ethanol concentration of 17.81 g/L was obtained after simultaneous saccharification and fermentation of the pretreated CS under the defined optimized conditions.