Hot-compressed Water Treatment Research Articles

Effects of Hot Compressed Water Treatment with Phosphoric Acid for Enzymatic Saccharification of Rice Straw

Rice straw was treated using hot compressed water with or without phosphoric acid for enzymatic saccharification. The yields of xylose and glucose obtained from the treatment of the rice straw using hot compressed water without phosphoric acid were low. However, when 0.7% phosphoric acid solution was added to hot compressed water, the yield of xylose increased remarkably, and the highest yield (71%) was obtained at 160°C. Furthermore, the yield of glucose from the treated rice straw by enzymatic saccharification using an enzyme cocktail with a cellulase loading of 2 FPU/g- rice straw was 86%. It clarified that the hot compressed water treatment with phosphoric acid was effective in lowering the enzyme loading compared with the original hot compressed water treatment.

Ethanol Production from Sasa senanensis Wastes Using Hot Compressed Water Treatment for Enzymatic Saccharification

The saccharification of the Sasa senanensis waste using hot compressed water treatment for enzymatic hydrolysis was investigated. Hot compressed water treatment of the Sasa senanensis waste was conducted at 180-260 °C and followed by enzymatic saccharification. After the enzymatic saccharification treatment, the highest total sugar yield (52 % on the feedstock base) was obtained from the Sasa senanensis waste pretreated at a temperature of 200 °C and holding time of 5 min. Glucose enzymatically produced was rapidly converted to ethanol within 8 h without any fermentation inhibitor. Approximately 100 % of theoretical yield of ethanol was obtained from glucose. The Sasa senanensis waste may be suitable for the feedstock of ethanol production from fermentable sugars because no inhibition was observed during the enzymatic saccharification and ethanol fermentation.

Production and characterization of cellulases and hemicellulases by Acremonium cellulolyticus using rice straw subjected to various pretreatments as the carbon source

Cellulases and hemicellulases are key enzymes in the production of alternative fuels and chemicals from lignocellulosic biomass—an abundant renewable resource. Carbon source selection is an important factor in the production of cellulases and hemicellulases. Rice straw – a potential ethanol source – has recently gained considerable interest in Asian countries. Here, we investigated the production of cellulases by using rice straw subjected to various pretreatments as substrates in order to produce cellulases at low costs; we also identified the enzymes’ characteristics. Rice straw cutter milled to <3 mm was pretreated by wet disk milling, dry ball milling, or hot-compressed water treatment (HCWT). Pretreated rice straw and commercial cellulose, Solka Floc (SF), were used as carbon sources for cellulase production by the fungus Acremonium cellulolyticus. Filter paper cellulase, β-xylanase, and β-xylosidase production from ball- and disk-milled samples were higher than those from SF. Enzymatic activity was absent in cultures where HCWT rice straw was used as carbon source. Wet disk-milled rice straw cultures were more suitable for enzymatic hydrolysis of pretreated rice straw than SF cultures. Thus, wet disk milling may be a suitable pretreatment for producing substrates for enzymatic hydrolysis and generating inexpensive carbon sources for cellulase production.

Enzymatic saccharification of woody biomass micro/nanofibrillated by continuous extrusion process II: Effect of hot-compressed water treatment

An extrusion process involving a twin-screw extruder was used for the micro/nanofibrillation of Douglas fir and Eucalyptus treated with hot-compressed water (HCW). Partial removal of hemicellulose and lignin by HCW treatment effectively improved the fibrillation by extrusion. Only HCW treatment produced glucose less than 5 weight percent (wt.%) in Douglas fir in a temperature range of 140-180 degrees C by enzymatic hydrolysis. Glucose production yields of 18 and 26 wt.% were obtained by HCW treatment at 170 and 180 degrees C, respectively, in Eucalyptus. Use of extrusion after HCW treatment drastically improved monosaccharide production yield in both woods. In the case of Douglas fir, the obtained values were 5 times higher than those obtained by HCW treatment alone. Total monosaccharide production yields were higher in Eucalyptus than in Douglas fir. The extruded production had a fine fibrous morphology on a sub-micro/nanoscopic scale. This result shows the great potential of the extrusion process after HCW treatment as a cost-effective pretreatment for enzymatic saccharification of woody biomass.

Increase in enzyme accessibility by generation of nanospace in cell wall supramolecular structure

An energy efficient nanofibrillation method that combines disk milling and mild hot-compressed water (HCW) treatment was developed to improve enzymatic accessibility of Eucalyptus wood. In this method, the residual product of HCW treatment was fibrillated by disk milling under wet conditions. Relatively moderate HCW treatment conditions (temperature below 180 °C and reaction time of 30 min) were adopted, and the amount of water used was only five times that of wood. These conditions were sufficient for the partial removal of hemicellulose and lignin from cell wall supramolecular structure to create nanospace between cellulose microfibrils. This morphological characteristic effectively improved nanofibrillation by disk milling. The fibrillated products with a size of less than 20 nm can be obtained after very short milling time, and this process drastically improved the enzymatic saccharification yield. The energy consumption was much lower than that of other mechanical methods for size reduction to give the same monosaccharide-recovery yield.

P-114 イナワラのリン酸水熱処理による酵素量の低減化(ポスター1,ポスター発表)

P-114 イナワラのリン酸水熱処理による酵素量の低減化(ポスター1,ポスター発表)

Ethanol production with β-xylosidase, xylose isomerase, and Saccharomyces cerevisiae from the hydrolysate of Japanese beech after hot-compressed water treatment

Ethanol was produced from the hydrolysate collected as the water-soluble (WS) portion after hot-compressed water (HCW) treatment of Japanese beech. The process involved saccharification with β-xylosidase followed by isomerization with xylose isomerase and fermentation with Saccharomyces cerevisiae. Several process schemes were compared to investigate the effect of process integration of saccharification, isomerization, and fermentation. Higher ethanol yields were obtained for the processes that integrated isomerization and fermentation or saccharification and isomerization. Integration of isomerization and fermentation was effective in converting xylose into ethanol. Similarly, integration of saccharification and isomerization was effective in converting xylooligosaccharides into xylulose. It is presumed that the saccharification reaction toward xylose and the isomerization reaction toward xylulose were linked and therefore each reaction was enhanced.

Process integration of ethanol production from Japanese beech as treated with hot-compressed water followed by enzymatic treatment

Ethanol was produced from the hydrolysate collected as a water-soluble (WS) portion and a residue after hot-compressed water (HCW) treatment of Japanese beech with and without fractionation. Simultaneous saccharification with β-xylosidase and isomerization with xylose isomerase followed by fermentation with Saccharomyces cerevisiae were applied to the WS portion; simultaneous saccharification with cellulase and fermentation with S. cerevisiae was applied to the residue. Integration of the processes for the WS portion and the residue was investigated to improve the conversion efficiency throughout the whole process. The ethanol yield in the integrated process without fractionation was comparable with that for the process with fractionation. Ethanol yields were improved for both of the processes by modifying the operation pattern in which cellulase was added prior to fermentation of the residue.

3-90-7 水熱/酵素糖化処理を利用したクマイザサからのエタノール生産(Session 3 バイオマス等,ポスター発表)

3-90-7 水熱/酵素糖化処理を利用したクマイザサからのエタノール生産(Session 3 バイオマス等,ポスター発表)

Enzymatic saccharification of water-soluble portion after hot-compressed water treatment of Japanese beech with xylanase and β-xylosidase

Enzymatic saccharifications of the hydrolysate collected as the water-soluble (WS) portion after hot-compressed water (HCW) treatment of Japanese beech with xylanase and β-xylosidase were performed to investigate the hydrolytic properties of these enzymes. The WS portions with different molecular weight distributions and initial concentrations of xylooligosaccharides were prepared as substrates, one of which contained mainly smaller xylooligosaccharides [degree of polymerization (DP) = 2 or 3], while the other contained larger xylooligosaccharides (DP ≥ 4). The highest xylose recovery was obtained from both of the WS portions treated with β-xylosidase rather than with xylanase. This suggests that β-xylosidase could have a higher activity than xylanase toward larger xylooligosaccharides (DP ≥ 4) as well as smaller xylooligosaccharides (DP = 2 or 3) recovered from HCW treatment. As a result, the use of β-xylosidase was found to be effective for saccharifi cation of the WS portion, even with a short reaction time for the HCW treatment.

Wet disk milling pretreatment without sulfuric acid for enzymatic hydrolysis of rice straw

Rice straw has recently attracted interest in Japan as a potential source of raw material for ethanol production. Wet disk milling, a continuous pretreatment to enhance the enzymatic digestibility of rice straw, was compared with conventional ball milling and hot-compressed water treatment. Pretreated rice straw was evaluated by enzymatic hydrolysis using Acremonium cellulase and characterized by X-ray diffraction and scanning electron microscopy. Glucose and xylose yields by wet disk milling, ball milling, and hot-compressed water treatment were 78.5% and 41.5%, 89.4% and 54.3%, and 70.3% and 88.6%, respectively. Wet disk milling and hot-compressed water treatment increased sugar yields without decreasing their crystallinity. The feature size of the wet disk milled rice straw was similar to that of hot-compressed water-treated rice straw. The energy consumption of wet disk milling was lower than that of other pretreatments. Thus, wet disk milling is an economical, practical pretreatment for the enzymatic hydrolysis of lignocellulosic biomass, especially herbaceous biomass such as rice straw.

Characteristics of Solid Residues Obtained from Hot-Compressed-Water Treatment of Woody Biomass

Hydrolysis experiment of woody biomass in hot compressed water (HCW) was conducted in a batch-type reactor and the characteristics of solid residue after the HCW hydrolysis treatment were measured to understand the hydrolysis mechanism of woody biomass. Woody slurry of Douglas fir was used in this HCW experiment. Reaction temperature was controlled from 423 to 523 K, and the reaction time was set at 1 min. After separation of solid residues from the hydrolysis liquid material, the solid residue characteristics, such as proximate and ultimate analysis, particle size distribution, particle shape, surface area, pore size distribution, chemical composition, and equilibrium moisture content ratio, were measured and then the decomposition mechanism of woody biomass in HCW was discussed. It was found that the solid residue characteristics yielded in HCW changed drastically depending on the reaction temperature. For example, cellulose crystallinity decreased with increasing reaction temperature, and the physical characteristics of solid residue, such as particle shape, particle diameter, and pore size distribution, also changed dramatically depending on the reaction temperature. The physical or chemical characteristic change in HCW was strongly related to the decomposition of components of woody biomass at that reaction temperature. Dehydration of woody components was one of the most important factors to understand physical characteristics during HCW treatment.

Solubilization and Saccharification of Barley Straw by Hot-Compressed Water Treatment

Solubilization and Saccharification of Barley Straw by Hot-Compressed Water Treatment

P-223 バッチ式加圧熱水処理におけるセルロースおよびその構成糖の分解挙動1(ポスター発表)

P-223 バッチ式加圧熱水処理におけるセルロースおよびその構成糖の分解挙動1(ポスター発表)

Combining hot-compressed water and ball milling pretreatments to improve the efficiency of the enzymatic hydrolysis of eucalyptus

BackgroundLignocellulosic biomass such as wood is an attractive material for fuel ethanol production. Pretreatment technologies that increase the digestibility of cellulose and hemicellulose in the lignocellulosic biomass have a major influence on the cost of the subsequent enzymatic hydrolysis and ethanol fermentation processes. Pretreatments without chemicals such as acids, bases or organic solvents are less effective for an enzymatic hydrolysis process than those with chemicals, but they have a less negative effect on the environment.ResultsThe enzymatic digestibility of eucalyptus was examined following a combined pretreatment without chemicals comprising a ball milling (BM) and hot-compressed water (HCW) treatment. The BM treatment simultaneously improved the digestibility of both glucan and xylan, and was effective in lowering the enzyme loading compared with the HCW treatment. The combination of HCW and BM treatment reduced the BM time. The eucalyptus treated with HCW (160°C, 30 minutes) followed by BM (20 minutes) had an approximately 70% yield of total sugar with a cellulase loading of 4 FPU/g substrate. This yield was comparable to the yields from samples treated with HCW (200°C, 30 minutes) or BM (40 minutes) hydrolyzed with 40 FPU/g substrate.ConclusionThe HCW treatment is useful in improving the milling efficiency. The combined HCW-BM treatment can save energy and enzyme loading.

Fractionation and Solubilization of Cellulose in Rice Hulls by Hot-Compressed Water Treatment, and Production of Glucose from the Solubilized Products by Enzymatic Saccharification

本論文では，籾殻中のセルロースからグルコースを生産する方法として，加圧熱水処理と酵素処理を組み合わせた方法について検討した．まず，200°C以下の加圧熱水処理により，ヘミセルロースおよび一部のリグニンを可溶化，分離後の試料を，パーコレータ型反応器にて加圧熱水処理（280°C, 10 MPa, 10 mL/min）し，セルロースを可溶化した．続いて，可溶化物をセルラーゼにて処理することで，セルロース基準で68.1%の収率でグルコースに変換することができた．

3-44 加圧熱水処理により得られるキシロオリゴ糖からのSSFによるバイオエタノール生産((12)水熱反応2,Session 3 バイオマス等,研究発表(口頭発表))

3-44 加圧熱水処理により得られるキシロオリゴ糖からのSSFによるバイオエタノール生産((12)水熱反応2,Session 3 バイオマス等,研究発表(口頭発表))

風化炭から加圧熱水により生成されたフルボ酸の化学的特徴

Fulvic acid becomes the most valuable humic substance because of the water-solubility and the physi-ological action. However, a little amount of fuvic acid is extracted in general from a variety of natural humic resources. Therefore, in this work, its preparation was examined by hot compressed water treatment of Xinjiang (China) weathered coal. The resulting water-soluble product was proved to be a sort of fulvic acid. The yield of the produced fulvic acid by this procedure was at most 26 [wt%]. The formed fulvic acid showed a higher content of oxygen and carboxyl group than those of the extracted one from the original weathered coal. Furthermore, the phenolic hydroxyl group content was higher than that of products of the ozone oxidation of humic acid from the same weathered coal, reported previously.

3-18.加圧熱水条件による木材の炭化((5)水熱II,Session 3 バイオマス等)

3-18.加圧熱水条件による木材の炭化((5)水熱II,Session 3 バイオマス等)