Publications by authors named "Yasumitsu Uraki"

Lignin-based carbon fibers (LCFs) with graphitized structures decorated on their surfaces were successfully prepared using the simultaneous catalyst loading and chemical stabilization of melt-spun lignin fibers, followed by quick carbonization functionalized as catalytic graphitization. This technique not only enables surficial graphitized LCF preparation at a relatively low temperature of 1200 °C but also avoids additional treatments used in conventional carbon fiber production. The LCFs were then used as electrode materials in a supercapacitor assembly.

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To elucidate the influence of polysaccharides on hardwood lignification, dehydrogenative polymerization of monolignols, coniferyl alcohol (CA) and sinapyl alcohol (SA), was attempted with recombinant cationic cell wall-bound peroxidase (rCWPO-C) and horseradish peroxidase (HRP) in measurement cells of a quartz crystal microbalance with dissipation (QCM-D). Hardwood cellulose nanofibers were anchored; hemicelluloses, xylan, partially acetylated xylan (AcXY), galactoglucomannan, and xyloglucan, and the enzymes were subsequently adsorbed onto the QCM-D sensor surface, enabling fabrication of artificial polysaccharide matrices. The largest amount of rCWPO-C is found to be adsorbed onto AcXY among all the polysaccharides, which affords the largest amount and size of spherical dehydrogenation polymers (DHPs) from both CA and SA.

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A bacterial strain, Pseudomonas bohemica strain ins3 was newly isolated as a resistant strain against high concentrations of hinokitiol. This strain was revealed not only to show resistance but also completely remove this compound from its culture broth. In addition, its mechanism was revealed to be independent of conventional aromatic dioxygenases, ie catechol-1,2- or 2,3-dioxygenases.

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Hinokitiol has a broad antibacterial activity against bacteria and fungi. While its biosynthetic pathway has been intensively studied, its dynamics in natural environments, such as biodegradation pathway, remain unclear. In this study, the authors report a direct deuterium labeling of hinokitiol as a traceable molecular probe to serve those studies.

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Despite the importance of litter decomposition under snow cover in boreal forests and tundra, very little is known regarding the characteristics and functions of litter-decomposing fungi adapted to the cold climate. We investigated the decomposition of oak leaves in a heavy snowfall forest region of Japan. The rate of litter weight loss reached 26.

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Amphipathic lignin derivatives (A-LDs) prepared from the black liquor of soda pulping of Japanese cedar are strong accelerators for bioethanol production under a fed-batch simultaneous enzymatic saccharification and fermentation (SSF) process. To improve the bioethanol production concentration, conditions such as reaction temperature, stirring program, and A-LDs loadings were optimized in both small scale and large scale fed-batch SSF. The fed-batch SSF in the presence of 3.

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To elucidate the influence of wood polysaccharide components on lignin formation in vitro, models for polysaccharide matrix in wood secondary cell wall were fabricated from two types of bacterial cellulosic films, flat film (FBC) and honeycomb-patterned film (HPBC), as basic frameworks by depositing xylan onto the films. An endwise type of dehydrogenative polymerization, "Zutropfverfahren", of coniferyl alcohol was attempted in the films with/without xylan. The resultant dehydrogenation polymer (DHP) was generated inside and outside xylan-deposited films, whereas DHP was deposited only outside the films without xylan.

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Amphipathic lignin derivatives (A-LDs) were already demonstrated to improve enzymatic saccharification of lignocellulose. Based on this knowledge, two kinds of A-LDs prepared from black liquor of soda pulping of Japanese cedar were applied to a fed-batch simultaneous saccharification and fermentation (SSF) process for unbleached soda pulp of Japanese cedar to produce bioethanol. Both lignin derivatives slightly accelerated yeast fermentation of glucose but not inhibited it.

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Several lignin model polymers and their derivatives comprised exclusively of β-O-4 or 8-O-4' interunitary linkages were synthesized to better understand the relation between the thermal mobility of lignin, in particular, thermal fusibility and its chemical structure; an area of critical importance with respect to the biorefining of woody biomass and the future forest products industry. The phenylethane (C6-C2)-type lignin model (polymer 1) exhibited thermal fusibility, transforming into the rubbery/liquid phase upon exposure to increasing temperature, whereas the phenylpropane (C6-C3)-type model (polymer 2) did not, forming a char at higher temperature. However, modifying the Cγ or 9-carbon in polymer 2 to the corresponding ethyl ester or acetate derivative imparted thermal fusibility into this previously infusible polymer.

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Several kinds of natural woods and isolated lignins with various syringyl to guaiacyl (S/G) ratios were subjected to thioacidolysis followed by Raney nickel desulfuration to elucidate the relationships between the S/G ratio and the interunit linkage types of lignin. Furthermore, enzymatic dehydrogenation polymers (DHP) were produced by the Zutropf (gradual monolignol addition) method from mixtures of various ratios of coniferyl alcohol and sinapyl alcohol. The analysis of DHPs and natural wood lignins exhibited basically a similar tendency.

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We describe the synthesis and NMR spectroscopic analysis of three artificial lignin polymers containing only the beta-O-4 substructure: syringyl-type homopolymer, p-hydroxyphenyl-type homopolymer and guaiacyl/syringyl-type heteropolymer. Using gel permeation chromatography, the weight-average degree of polymerization (DP(w)) of the three polymers was determined as 19.2, 38.

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Human immunodeficiency virus type 1 (HIV-1) is a cytopathic retrovirus and the primary etiological agent of acquired immunodeficiency syndrome (AIDS) and related disorders. In cells chronically infected with HIV-1, nuclear factor-kappaB (NF-kappaB) activation by external stimuli such as tumor necrosis factor alpha (TNFalpha) augments replication of HIV-1. NF-kappaB involves in many diseases such as inflammation, cancer, and Crohn's disease.

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An artificial lignin polymer containing only the beta-O-4 substructure was synthesized. The procedure consists of two key steps: 1) polycondensation of a brominated monomer by aromatic Williamson reaction; and 2) subsequent reduction of the carbonyl polymer. 13C-NMR and HMQC spectra of the polymer were consistent with beta-O-4 substructures in milled wood lignin isolated from Japanese fir wood.

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Honeycomb and stripe patterned films were prepared from cellulose triacetate (CTA)/chloroform solution, as a result of the self-organization of the polymer during evaporation of the solvent. The honeycomb patterned CTA films were prepared by two methods, a direct pattern formation method and a transcription method. The latter method gave a well-organized microporous honeycomb pattern.

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The beta-O-4 structure is the most abundant substructure in lignin. Lignin related polymers composed of only the beta-O-4 structure were prepared using simple aromatic compounds as starting materials. Acetophenone derivatives were brominated, polymerized in the presence of K2CO3 and reduced with NaBH4 to give the lignin related polymers.

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Lignin gels were prepared from acetic acid lignin by use of polyethylene glycol diglycidyl ether as cross-linker. The gels were found to swell in aqueous ethanol solution, in particular 50% (v/v) solution. In addition, they also swelled in alkaline solution and shrank upon heating.

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