Pretreatment of sugarcane bagasse using ionic liquid for enhanced enzymatic saccharification and lignin recovery: process optimization by response surface methodology

Using Ionic Liquids (ILs) to convert lignocellulosic biomass (LCB) to high-value products has emerged as an environmentally benign process. The present study reports the potential of recovering reducing sugars and lignin from sugarcane bagasse (SCB) using two novel ILs, N, N-Diisopropylethylammonium hydrogen sulfate (IL-1) and N, N-Diisopropylethylammonium perchlorate (IL-2). The process parameters—reaction temperature, time, and IL concentration have been optimized using the Response surface methodology (RSM). At optimum reaction conditions, a reducing sugar yield of 53.4 ± 0.25% and 55.93 ± 0.7%, and lignin recovery of 28.92 ± 0.23% and 31.35 ± 0.45% were obtained for IL-1 and IL-2 , respectively. The effect of ILs-based pretreatment on SCB was investigated by using Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance ( 1 H-NMR), powder X-ray diffraction (P-XRD), and scanning electron microscopy (SEM) analysis. Enzymatic hydrolysis of the IL-1 and IL-2 pretreated SCB has shown a 3.9 and 4.7-fold increase in saccharification efficiency compared to raw SCB. The compositional changes of ILs during recycling have been analyzed using 1 H-NMR analysis. The IL reuse and recyclability studies demonstrate that both recycled ILs could be utilized till the fourth cycle.