Yoshio Harano

Microwave treatment of cellulosic materials for their enzymatic hydrolysis

SummaryRice straw and bagasse with water content 84 or 94% were irradiated with microwave (2450MHz) in sealed glass vessels. This treatment enhanced markedly the accessibility of the cellulosic materials for the enzymatic hydrolysis: for example, 1.6 times in the rice straw by the microwave treatment at 170 °C for 5 min and 3.2 times in the bagasse by the treatment at 200 °C for 5 min, compared with the untreated.

Pretreatment of bagasse by nonionic surfactant for the enzymatic hydrolysis

Abstract Enzymatic hydrolysis of bagasse was accelerated by pretreatment with 3·33% wt nonionic surfactant (Tween 20; polyoxyethylene sorbitan monolaurate) at 170–190°C. The amount of the lignin remaining in the pretreated bagasse decreased by about 22–27% and the enzymatic hydrolysis rate increased, because of an increase in the surface area of cellulose accessible to enzyme, compared to those pretreated with water. This effect is based on the fact that surfactant makes hydrophobic degradation products extractable to water. The pretreatment effect varied with the HLB (hydrophile-lipophile balance) values of surfactant. The hydrophilic surfactant having high HLB values was useful for the extraction of hydrophobic degradation products from lignin and hemicellulose. In the pretreatment at 190°C, an addition of Tween 20 to the UCT-solvent (binary solvent with water, having upper critical-temperature in the manual solubility curve) increased the effect of UCT-solvent pretreatment. This is because the surfactant makes the separation of the degradation products easier.

Synthesis of aspartame precursor by solid thermolysin in organic solvent

SummaryThe enzymatic synthesis of a peptide compound was carried out successfully in homogeneous organic solvent.Solid Thermolysin was found to catalyze the synthetic reaction of N-benzyloxycarbonyl-L-aspartyl-L-phenylalanine methyl ester (Z-APM; a precursor of sweetner Aspartame) from N-benzyloxycarbonyl-L-aspartic acid (Z-L-Asp) and L-phenylalanine methyl ester (L-PheOMe) in a 98 percent organic medium (ethylacetate∶benzene∶methanol∶water=50∶29∶19∶2). The dissolution of enzyme was not observed. The optimal pH shifted to acidic side by 1.0 pH unit, compared with that in aqueous medium. The enzymatic activity of solid thermolysin with an average size of 3.4×9.5 μm was determined to be 0.18 μmoles-product/(mg-solid)·h under the initial concentrations of L-PheOMe of 0.1M and Z-L-Asp of 0.05M, and at pH 6.0 and 40°C.

Effects of agitation on enzymatic saccharification of cellulose

SummaryCrystalline cellulose Avicel has been hydrolyzed byTrichodermaviride cellulase (Meicelase CEPB) under vaned agitation conditions and the effect of agitation on the adsorption of cellulase on cellulose has been studied. Agitation was found to enhance the hydrolysis pf crystalline cellulose; possibly the agitation enhances the adsorption of exoglucanase to shift the adsorption balance of exoglucanase and endoglucanase to a direction favorable for their synergistic action on the surface of cellulose.

Mechanism of crystallization of enzyme protein thermolysin

Abstract The mechanism of crystallization of enzyme protein thermolysin was investigated. The size distribution of thermolysin precipitates was measured by dynamic light scattering during precipitation, and the surface and cross section of the finally obtained precipitate were observed by scanning electron microscopy. The thermolysin precipitates obtained at the initial supersaturation ratio of 8.9 to 164 and pH 7.0 were hexagonal rods having an average size of 9.2×1.5 μm, and were composed of a number of small particles of 15 to 200 nm in diameter. The average size of the small particles was 60 nm in diameter, and the formation of the particles was found to be completed in the early stage of precipitation. Observation of the finally recovered thermolysin precipitate by polarizing microscopy revealed that the precipitate is a crystalline solid. From these data, a possible mechanism of thermolysin crystallization was proposed. The crystallization proceeds through two steps: the first step is the formation of primary particles, and the second step is crystal growth by highly ordered aggregation of the primary particles.

Characteristics of immobilized invertase: IMMOBILIZED INVERTASE

Five kinds of immobilized invertases (IMI)—covalently of porous glass and ion‐exchange resins and ionically on ion‐exchange resins—have been prepared and their kinetic characteristics for sucrose hydrolysis, such as Km, K, pH profile, and thermal stability were studied. Comparing the values of Km and activation energy and the entropy of IMI with those of native invertase, it was concluded that the immobilization influences not binding but kinetic specificity. The effects of the immobilization method on thermal stability were also discussed.

Kinetic study on thermal stability of immobilized invertase

The kinetic study of the thermal stability of three kinds of invertases: native, immobilized on porous glass covalently, and on ion‐exchange resin ionically, has been carried out, measuring their enzymatic activity for sucrose hydrolysis. Thermal deactivations of all invertases obeyed first‐order kinetics, being independent of substrate concentration, with kd and ΔEd, ΔSd* as shown in Tables I and II, respectively. Based on these parameter values, the effects of immobilization and pH at deactivation on the stability have been considered, and it was suggested that the ionic bond gives a more loosely deformed enzyme than the covalent bond.

Applicability of an empirical rate expression to enzymatic hydrolysis of cellulosic materials

SummaryThe empirical rate expression previously proposed for the hydrolysis of avicel and tissue paper by Meicelase from Trichoderma viride also held for the hydrolysis of dewaxing cotton, Whatmann CF-11, Solka Floc SW-40, tissue paper and 1% NaOH-pretreated sawdust by Meicelase, Trichoderma reesei QM9414 or Cellulosin from Aspergillus nigar.

NiO deposition on support during preparation of Ni/SiO2 catalyst by chemical vapor deposition.

化学気相析出法 (CVD) により調製したNiO/SiO2粒子は数十nmのNiOとsiO2の凝集体と考えられる.この粒子の生成環境は自由分子領域にあり, NiO, SiO2蒸気の過飽和度Sは反応温度, 反応管内の位置により異なるが最大1020のオーダーである.そして, 核化速度はきわめて速い.そこで, 粒子生成過程はブラウン凝集過程であるとし解析し, 反応管軸方向温度補正を加えると, 粒子径dと滞留時間τとの間には, d=ατ2/5の関係が得られた.さらに, 単一のNiO粒子成長系から得た付着係数はNiO/SiO2系中から求めた値と比較して, 明らかに単一粒子系の付着係数が大きく, その割合はNiOの含有量にほぼ一致した.以上のことから, NiO/SiO2系のNiO粒子の成長はSiO2粒子により抑制されるが, SiO2 matrix中へのNiO粒子の均一分散には有利であることが明らかとなった.

Effects of sulfur on reduction behavior of supported NiO.

触媒の担体として広く用いられている Neobead-Cは不純物として硫黄化合物を含んでいる.そして, この硫黄は IR吸収スペクトル測定により SO42-の形で存在することが明らかとなった.本報では Neobead-C中のこの硫黄化合物が触媒前駆物質である担持 NiOの水素による還元に与える効果を調べた.この硫黄化合物は773Kでの水素還元ではほとんど除去されない.水素還元-酸素酸化を繰り返し, 水素, 酸素の消費量, 捕集された H2S, SO2の量を測定し, Neobead-C中の SO42-イオンの還元プロセスを考察した.NiOの還元に必要な量論量より過剰の水素が消費されているにもかかわらず, Neobead-Cに担持した NiOは773Kでは還元されにくい. Neobead-Cと同様, 還元-酸化を繰り返した結果から, Nioの還元性は SO42-により抑制されることが明らかとなった.還元-酸化の繰り返し実験から, 1回だけ含浸, 〓焼を施したγ-AM3.5とγ-AI13.5中の NiOの還元率は除去された SO42-と担持 Niのモル比 (S/Ni) が0.3になるまで0.3に達しない.しかし二回含浸, 〓焼した γ-AM6.0は (S/Ni) 比が0.1近傍になるまで還元率は0.5に近づく.これらの事実は前者の触媒では1回しか〓焼していないが, 後者の触媒は2回の〓焼で担体と強く結合し, 初めに担持したNi部分は還元しにくいことを示唆している.