Table 3.

Hydrolysis of pretreated wheat straw with recycled enzymes

Enzymes in recycling experiments	Hydrolysis yield, % of total carbohydrates
Small-scale
Reference (fresh CBM-lacking enzymes)	41.9 (1.2)
Recycled 100% (CBM-lacking enzymes)	38.9 (0.7)
Large-scale
Reference CBM-containing (100%)	53.6 (4.0)
Reference CBM-lacking (100%)	52.1 (0.4)
Recycled CBM-lacking (100%)	30.9 (1.1)
Recycled CBM-lacking (70% + fresh 30%)	45.9 (4.3)

Hydrolysis yields by recycled enzymes in small- (20% DM) and large-scale (25% DM) hydrolysis experiments of pretreated wheat straw for 72 hours at 50°C. In small-scale experiments the Thermoascus aurantiacus enzymes CBH I (CBM-), EG II, XYL and BG were collected after first hydrolysis (72 hours at 50°C), concentrated and dosed on the same protein load (10 mg/g DM) as the reference enzyme mixture. In large-scale experiments the enzymes were collected after fermentation and concentrated for reuse. Protein dosage in all experiments was 10 mg/g DM. Enzymes used in small-scale experiments were heat treated prior to first hydrolysis, while not in the large-scale experiments. The ratio of enzymes (protein-based) for the first hydrolyses was CBH I:EG II:XYL:BG 15:3:2:1. Hydrolysis yields are expressed as the percentage of total carbohydrates, measured as reducing sugars and the standard deviations are in parentheses. BG, β-glucosidase; CBH, cellobiohydrolase; CBM, carbohydrate-binding module; DM, dry matter; EG, endoglucanase; XYL, xylanase.