The combined pretreatment using ultrasonication with different chemical pretreatments to enhance lignin production and enzymatic hydrolysis efficiency

Sugarcane bagasse is a lignocellulosic biomass and an abundant agricultural residue in Thailand. Therefore, it has been studied to maximize and convert it into high value bioproducts. However, due to its complex structure, pretreatment processes are important for enhancing the efficiency of component recovery. This study presents the combined ultrasonication and chemical pretreatment methods, specifically alkaline pretreatment and deep eutectic solvent (DES), to investigate their effects on lignin yield and enzymatic hydrolysis efficiency. The study examined the use of ultrasonication with 1M sodium hydroxide (Power rate 60%, 30 min) and the process sequence between ultrasonication before alkaline pretreatment (UBA) and ultrasonication after alkaline pretreatment (UAA) under the same conditions. Results showed that UBA obtained the highest lignin yield of 94%. The enzyme hydrolysis efficiency has higher reduced sugar yields from 44 to 189-190 mg/g biomass. In terms of DES pretreatment using a mixture of choline chloride-ethylene glycol-lactic acid (ChCl-EG-LA), different solid-liquid ratios 1:20 (20DES) and 1:40 (40DES). Lignin yields are 30% and 12%, respectively, which were less than those of ultrasonic combined with alkaline. The enzyme hydrolysis efficiency of 20DES has reducing sugar yields 186.79 mg/g biomass, while 40DES has highest reducing sugars yields 186.79 mg/g biomass.