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Research paper : Bioethanol production from woods with the aid of nanotechnology (T. Endo)−277−Synthesiology - English edition Vol.2 No.4 (2010) min or less, no major change was seen, while saccharification significantly improved in the wet-treated product obtained after dry treating for 20 min or more. When the dry mechanochemically treated product was observed by a scanning electron microscope (SEM), it was found that the large wood structure of the raw wood powder was almost entirely destroyed by the 20-min dry mechanochemical treatment. Since the ball mill process was not practical for destroying the hoop structure, we considered the method that had relatively large milling energy and enabled mass processing, and found that wet cutter mill was effective. The wet cutter mill we employed (Micro-Meister; Masuko Sangyo Co., Ltd.) had powerful shear force with a fixed blade and a rotary blade that rotated at ultra high-speed of 10,000 rpm or more, and was capable of instantly breaking down the raw material dispersed in water to 1 mm or less. In this case, water fluidized the milled product, prevented stagnation, and promoted the break down efficiently. Also, the water that permeated the wood structure during the process also worked effectively for the following autoclave and disk mill treatments.Next, we conducted the hydrothermal treatment using the autoclave as a method for reducing the adhesion effect of hemicellulose. The hydrothermal treatment allowed the selective hydrolysis of hemicellulose component according to the temperature condition[13]. Investigating a combination treatment method that combined the wet cutter mill and autoclave treatments, it was found that efficient pretreatment was possible regardless of the wood species by conducting the autoclave treatment (135 ºC) after conducting the wet cutter mill treatment (1 mm or less) on the roughly milled raw wood powders, and then conducting the disk mill treatment as the final stage. When the Eucalyptus raw material was roughly milled to 3 mm or less by the combined treatment, the degree of saccharification was 4 times or more compared to the case when wood powder 0.25 mm, which was finer, was treated with the disk mill only. Approximately the same saccharification was obtained as for the long dry ball milling (Fig. 8).6.3 Mechanism of improvement of enzymatic saccharification by combination wet mechanochemical treatmentThe mechanism by which the enzymatic saccharification improves due to the aforementioned combination wet mechanochemical treatment is thought to be as follows Fig. 9 Size image of combination wet mechanochemical treatment.Fig. 8 Increasing efficiency of disk mill treatment by combination treatment.Enzymatic saccharification time (h)Cellulose saccharification (%)0101030304050607080902002040Untreated Eucalyptus 0.2 mmEucalyptus 0.25 mm, wet disk millEucalyptus 3 mm, wet cutter mill + wet disk millEucalyptus 3 mm, autoclave + wet disk millEucalyptus 3 mm, wet cutter mill + autoclave + wet disk millEucalyptus 0.2 mm, dry milling 4 h (for comparison)SizeWoodWood structureCellulose moleculeRaw materialWood fiberCellulose microfibrilPrimary wallIntercellular layer20~500 µm0.5 nm2~60 µmHemicellulose lignin ~100 nm~10 µm~3~5 nm6 fibers6 fibersEnzyme saccharization1 m1 mm100 µm100 nm1 nmGlucoseGoalCellulose nanofiberEnzymes can approach easily, saccharification progressesPartial removal of hemicelluloses that act as adhesiveDestruction of microfibril layer corresponding to hoopEnzymeIncreased efficiencyRough milling treatmentSeparation of microfibrilWet disk mill treatmentPartial decomposition of wood componentAutoclave treatmentIncreased permeability of waterDestruction of wood structureWet cutter mill treatment300 nmS3 layerS2 layerS1 layerSecondary wall

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