Comparison of heating methods in corn cob pretreatment by 1-butyl-3-methylimida zolium tetrafluoroborate and dimethylsulfoxide to enhance the enzymatic hydrolysis

Ionic liquid (IL) is one of the most widely applied chemical pretreatment methods in delignification to enhance the enzymatic hydrolysis of biomass pretreatment. However, the costs of ILs are high when compared with other methods. Among them, 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) is cheaper, but its limitation is due to fact that ‘’F- complex cannot be easily separated from [BMIM]BF4, resulting in [BMIM]BF3- which is capable of breaking down H-bonds. This limitation is recently solved by using the low-toxic solvent as a dimethyl sulfoxide (DMSO). In this work, a study of delignification for enhancing the digestibility of enzymatic with different heating methods is presented. Corn cobs are pretreated with [BMIM]BF4: DMSO. Afterwards, temperature of substrate is increased by hot air oven, autoclave and hot plate to 120°C for 3 hours. It was discovered that delignification with hot air oven is higher than the delignification with autoclave and hot plate by 1.73 and 2.02 folds. According to XRD analysis, the lignocellulosic structures of substrates are more damaged by heating with hot air oven and autoclave than by heating with hot plate, as evidenced by CI values (27.17, 24.22 and 30.18, respectively). In terms of enzymatic digestibility, the hot air oven has the maximum cellulose conversion of 85.51 percent, while autoclave and hot plate have 79.78 and 69.76 percent. Furthermore, 5-hydroxymethyl-2-furaldehyde (HMF), known as an inhibitor, cannot be detected by heating with hot air oven. The results suggest that the heating method by hot air oven for [BMIM]BF4: DMSO pretreatment is an excellent alternative.