Investigation of fermentable sugar production through microwave-assisted alkali pretreatment and subsequent acid hydrolysis on Prosopis juliflora biomass

Abstract

This study investigates the potential for producing fermentable sugars from Prosopis juliflora stem biomass using an unique approach using microwave-assisted KOH pretreatment. Various operating parameters in the microwave-assisted KOH pretreatment involves KOH conc (1, 2% and 3%), biomass loading (1, 3 and 5 g), microwave power (150, 300 and 450 W) and irradiation time (3, 4 and 5 min) were optimized by response surface methodology (RSM) using Box-Behnken Design (BBD). Hydrolysis was also optimized using various concentrations of sulphuric acid (1, 3, 5, 7% and 9%) for 60 min at 120 °C to produce fermentable sugars which was compared with the liquid obtained after the pretreatment. The native and the pretreated P. juliflora stem biomass was characterized by scanning electron microscope (SEM). Under the optimized conditions (2% KOH, 5 g biomass loading, 150 W, 4 min, followed by 5% H 2 SO 4 hydrolysis at 121 °C for 60 min), a maximum reducing sugar concentration of 2.25 mg/mL (225 mg g -1 biomass) was achieved. The integrated microwave-assisted alkaline pretreatment significantly enhanced biomass deconstruction and fermentable sugar recovery while employing low chemical concentration and short processing time. These findings demonstrate that P. juliflora stem biomass is a promising lignocellulosic feedstock and that the proposed low-severity, scalable pretreatment strategy has considerable potential for sustainable and economically viable bioethanol production.