3.4. Viscosity reduction of cassava substrates
Having demonstrated that the crude multi-enzyme contains all the activities required for degradation of plant cell wall, viscosity reduction of different cassava feedstocks using the multi-enzyme preparation was tested under VHG conditions. Fresh root mashat 32% initial solid content had a high viscosity of 12,841 mPa s,which resulted in difficulty in mixing, and thus the root mash couldnot be effectively hydrolyzed to sugars using the conventional pre-gelatinization/liquefaction method. Mechanical treatment by shearing and mixing for up to 2 h could reduce the viscosity by 28.0%. Next, fresh root slurry was treated with the multi-enzyme at 0.25–2.50% (w/w), equivalent to 1.96–19.61 IU/gsubstrate of carboxymethy lcellulose, 0.02–0.22 IU/gsubstrateof FPase,0.73–7.26 IU/gsubstrateof xylanase, 2.41–24.10 IU/gsubstrate of polygalacturonase, 9.55–95.53 IU/gsubstrateof -glucanase, and 1.46–14.60 IU/gsubstrate of mannanase. The maximum reduction of viscosity (98.5%) was achieved by incubation for 120 min with 2.5% multi-enzyme loading (Fig. 2a). Incubation with the multi-enzymefor the same duration, but at a lower loading of 0.5% was almost as