Hou-min Chang

... Forests No. 44, 183—193. (Japanese; English summary) Kirk, TK 1971. Effects of microorganisms on lignin. Ann. ... IUFRO Meeting, Div. 5, CSIR South Africa, Pretoria 1973. Wilcox, WW 1968. Changes in wood microstructure through progressive stages of decay. US Forest Serv. ...

We have studied the electrical-transport properties of individual single-crystalline IrO2 nanorods (NRs) prepared by MOCVD. With the help of e-beam lithography, individual NRs are contacted by Cr/Au submicron electrodes from above. Utilizing different probe configurations, not only the intrinsic properties of the NRs but also the temperature dependence of the contact resistance, Rcontact, has been determined down to liquid-helium temperatures.

The effects of ozone and chlorine dioxide on the structure of hardwood cellulose fibers were studied by chemical methods. Chlorine dioxide had very little effect on the cellulose degree of polymerization (DPv), although 40 - 50% of the chlorine dioxide charged was consumed. By contrast, ozonation of the cellulosic fibers resulted in a sub- stantial reduction in the cellulose DPv.

... 1986. Structural changes in lignin during oxygen bleaching. Nordic Pulp and Paper Research Journal. 3, 14–17. Gierer, J. 1980. Chemical aspects of kraft pulping. Wood Sci. Technol. 14, 241–266. Gierer, J., E. Yang and T. Reitberger. 1994. ...

Summary Peroxymonophosphoric acid (Pp) has been shown to be an excellent delignification chemical for kraft pulps. However, the reaction mechanism of Pp with lignin has not been elucidated. Therefore, the reactions of Pp with non-phenolic lignin model ...

Summary In peroxymonosulfuric acid bleaching, the presence of hydrogen peroxide is dependent on the reaction conditions and the conversion ratios used to generate the peroxy acid. Substantial amounts of hydrogen peroxide may be present in the reaction system ...

Iridium dioxide (IrO2) nanorods have been prepared by metal-organic chemical vapor deposition method. Applying the standard electron-beam lithography technique, a single nanorod with a diameter of 110 nm is contacted by three Cr/Au fingers from above. The resistance measurements on this nanorod have been performed between 10 and 300 K, using different probe configurations. We observe that the resistivity &rgr;

Kinetic and reaction mechanism of non-phenolic lignin model compounds under anaerobic polyoxometalate (POM), Na5(+1.9)(SiV1(-0.1)MoW10(+0.1)O40), bleaching conditions were examined. Analyses using a syringyl type model, 1-(3,4,5-trimethoxyphenyl)ethanol (1), a guaiacyl type, 1-(3,4-dimethoxyphenyl)ethanol (2), and 1- (4-ethoxy-3,5-dimethoxyphenyl)ethanol (3) suggest the significance of steric factor in POM oxidation of these compounds. A kinetic isotope effect was observed in isotope labeling experiments. It is suggested that the rate-determining step of POM oxidation of non-phenolic lignin model compound is the abstraction of benzylic hydrogen. An α-carbonyl type model compound, 1- (3,4,5-trimethoxyphenyl)ethanone (6), was degraded by the same rate with 1 while 3,4,5-trimethoxybenzaldehyde (7) was fairly stable. The existence of carbon-hydrogen bond at the β-position could be necessary for POM oxidation of α-carbonyl compound. A carbohydrate model compound, methyl β-D-glucopyranosi...

Dihydroconiferyl alcohol glucoside has been synthesized from cinnamic acid ethyl ester glucoside. Two reaction systems were investigated; one involving hydrogenation of the cinnamic acid ethyl ester glucoside intermediate followed by dii- sobutylaluminium hydride (DIBAL-H) reduction of the ester to the alcohol, and the other involving DIBAL-H reduction of the cinnamic acid ethyl ester to the alcohol (coniferin) followed by hydrogenation.

The structures of milled wood lignin (MWL) and cellulolytic enzyme lignin (CEL) have been analyzed using traditional chemical methods and solution-state NMR techniques. Comparisons of the results obtained reveal that subtle differences exist between the two lignin preparations. Thioacidolysis produced higher monomer yields from CEL than MWL, suggesting MWL has a more condensed structure. Quantitative (13)C NMR determined the degree of condensation in MWL to be 0.43 unit per aromatic moiety as compared to 0.36 in CEL. The MWL also contained a lower amount of beta-O-4' substructures per aromatic ring than CEL, 0.41 versus 0.47, respectively. Carbohydrate analysis revealed that the MWL may contain a higher proportion of middle lamella material as compared to the CEL. Because the middle lamella is considered to have a more condensed lignin structure, on the basis of the bulk polymerization theory, these results could explain the differences in beta-O-4' and degree of condensation.

A rapid transmittance near-infrared (NIR) spectroscopic method has been developed to characterize the lignin content of solid wood. Using simple, multiple regression, and partial least-squares statistical analysis the lignin contents of wood wafers, taken from increment cores, and synthetic wood, prepared by blending milled wood lignin and holocellulose, were compared and quantified. Strong correlations were obtained between the predicted NIR results and those obtained from traditional chemical methods. In addition to the experimental protocol and method development, NIR results from wood samples with different particle sizes and various lignin contents are discussed.

Cellulolytic enzyme lignin (CEL) and milled wood lignin (MWL) were prepared by three different ball-milling meth-ods. The structure of CEL at various yields was eluci-dated and compared with MWL using wet chemical analysis, FTIR and solution-state NMR techniques. Results ...

... Oktober 1975 Comparative Studies on Cellulolytic Enzyme Lignin and Milled Wood Lignin of Sweetgum and Spruce1'2) ... Keywords Milled wood lignin Cellulolytic enzyme lignin Enzyme lignin Liquidambar styraciflua Picea abies Sweetgum Spruce ...

Multi-stage and single-stage enzymatic hydrolysis of cellulose (Avicel PH-101) were conducted to investigate individual factors that affect the rate-reducing kinetics of enzymatic hydrolysis. Understanding factors affecting enzymatic hydrolysis of Avicel will help improve hydrolysis of various biomasses. Product inhibition, enzyme deactivation, and the changes of substrate are potential factors that can affect the hydrolysis efficiency of Avicel. Multi-stage enzymatic hydrolysis resulted in 36.9% and 25.4% higher carbohydrate conversion as compared to a single-stage enzymatic hydrolysis with an enzyme loading of 5 and 20 FPU/g in a 96 h reaction. However, a decline in carbohydrate conversion of 1.6% and 2.6% was observed through each stage with 5 and 20 FPU/g, respectively. This indicated that the substrate became more recalcitrant as hydrolysis progressed. The decreased reactivity was not due to crystallinity because no significant change in crystallinity was detected by X-ray diffraction. Product inhibition was significant at low enzyme loading, while it was marginal at high enzyme loading. Therefore, product inhibition can only partially explain this decreased conversion. Another important factor, enzyme deactivation, contributed to 20.3% and 25.4% decrease in the total carbohydrate conversion of 96 h hydrolysis with 5 and 20 FPU/g, respectively. This work shows that an important reason for the decreased Avicel digestibility is the effect of enzyme blockage, which refers to the enzymes that irreversibly adsorb on accessible sites of substrate. About 45.3% and 63.2% of the total decreased conversion at the end of the 8th stage with 5 and 20 FPU/g, respectively, was due to the presence of irreversibly adsorbed enzymes. This blockage of active sites by enzymes has been speculated by other researchers, but this article shows further evidence of this effect.

In this work, mixed hardwoods were pretreated by sodium sulfite-formaldehyde (SF). The effects of SF pretreatment on the chemical compositions and enzymatic hydrolysis of mixed hardwoods were investigated. SF pretreatment temperature had a significant effect on pulp yield and delignification, resulting in an increased efficiency of enzymatic hydrolysis. After 96 h of enzymatic hydrolysis at the cellulase loading of 40 FPU/g substrate, the yields of glucan and xylan on the basis of original wood were 37% and 11% for the pulp produced with 12% sulfite charge at 170 °C for 2 h. The total sugar recovery based on the sugar in original wood was 74%. These results indicate that sulfite-formaldehyde cooking is of great potential to be a pretreatment method for a greenfield mill to produce fuel ethanol from hardwood.

Enzymatic hydrolysis of insoluble biomass is a surface reaction. Part of the enzyme adsorb on the surface of biomass, whereas the others stay in the liquid phase. In this study, three substrates (Avicel cellulose, bleached hardwood pulp, and green-liquor pretreated hardwood pulp) were used to study the reactivity of bound and free enzyme. In a continuous enzymatic hydrolysis, 35-65% initially added enzymes became bound enzymes, which were primarily responsible for enzymatic hydrolysis. The contribution from free enzymes became insignificant after a certain period of reaction time. SDS-PAGE analysis showed that CBH I was significantly decreased in the free enzyme, which might be the reason for the low digestibility of free enzymes due to the loss of synergistic effect. When Tween 80 was added during enzymatic hydrolysis, the digestibility of free enzyme on Avicel was greatly enhanced. However, the benefit of surfactant was not noticeable for lignocellulosic pulps, comparing to Avicel.