Table 1 Several common pretreatment methods for lignin removal and their effects on enzymatic hydrolysis
Substrate | Pretreatment | Enzymatic hydrolysis | Lignin removal/% | Result | Refs. |
|---|---|---|---|---|---|
Wheat straw | 2% NaOH, 80 °C, and 2 h | 10%, 150 rpm, 50 °C, 72 h, and pH = 4.8 | 71.8 | Increasing the hydrolysis yield by 32.4% | [39] |
Corn stover | NaOH + Na2S, 8% total titratable alkali, 40% sulfidity, 140 °C, and 1 h | 5%, 180 rpm, 50 °C, 48 h, and pH = 4.8 | 45.0 | The original polysaccharides conversion: 70.0% | [40] |
Barley straw | 2% NaOH, 105 °C, and 10 min | 1%, 180 rpm, 50 °C, and pH = 4.8 | 84.8 | The reducing sugar yield: 86.5% | [41] |
Corncob | 12% sodium sulfite, 160 °C, 20 min and pH = 7 | 2%, 95 rpm, 50 °C, 48 h, and pH = 4.8 | 77.4 | Increasing the glucose yield by 20.1% | [25] |
Wheat straw | 20% ammonium sulfite, 4% sodium carbonate, 180 °C, and 1 h | 2%, 50 °C, 24 h, and pH = 5.0 | 82.6 | 99.9% of glucan and 88.0% of xylan were hydrolyzed | [26] |
Eucalyptus | 50% 2-propanol, 220 °C, and 2 h | 5%, 150 rpm, 50 °C, 72 h, and pH = 4.8 | 81.3 | The glucose yields: 88.6% | [42] |
Wheat straw | 70% Glycerol, 220 °C, and 3 h | 2%, 150 rpm, 50 °C, 24 h, and pH = 4.8 | 65.0 | The reducing sugar conversion: 90.0% | [43] |
Eucalyptus | 80% tetrahydro-2-furanmethanol, 1% HCl, 120–180 °C, and 30 min | 2%, 150 rpm, 50 °C, 72 h, and pH = 4.8 | 94.0 | The hydrolysis conversion: 94.2% | [44] |
Corncob | Choline chloride: Glycerol (1:2), 90 °C, and 24 h | 0.25%, 180 rpm, 50 °C, 72 h, and pH = 4.8 | 87.6 | The glucose yield: 85.3% | [32] |
Eucalyptus | Choline chloride: lactic acid (1:10), 110 °C, and 6 h | 2%, 150 rpm, 50 °C, 72 h, and pH = 4.8 | 80.0 | The glucose yield: 94.3% | [45] |
Corncob | Choline chloride: imidazol (3:7), 150 °C, and 15 h | 6%, 180 rpm, 50 °C, 80 h, and pH = 4.8 | 88.0 | The glucose yield: 94.6% | [46] |
Corn stalk | N-methyl-2-pyrrolidonium chloride/H2O, 90 °C, and 30 min | 1%, 150 rpm, 50 °C, 72 h, and pH = 4.8 | 85.9 | The glucose yield: 79.6% | [47] |
Switchgrass | 1-Ethyl-3-methylimidazolium acetate,160 °C, and 3 h | 0.5%, 150 rpm, 50 °C, 24 h, and pH = 4.8 | 69.2 | The glucose yield: 96.0% | [48] |
Rice straw | 1-Buthyl-3-methylimidazolium acetate, 120 °C, and 5 h | 3%, 100 rpm, 45 °C, 72 h, and pH = 4.8 | 41.4 | The glucose yield: 95.9% | [49] |