Publishing type：Research paper (scientific journal)   Kind of work：Joint Work  

DOI： 10.1038/s41598-018-36306-2

Publishing type：Research paper (scientific journal)  

Methods to control the particle sizes of active pharmaceutical ingredients were investigated using sodium ecabet (Na-ECA) hydrate, which tends to generate large plate-like crystals, as a model compound. In batch-cooling crystallization in H2O, the particle size decreased as the cooling rate was increased. Although the particle size reached 97 µm at a cooling rate of 40°C/h, this may be too large for formulation without further physical processing. A series of semi-batch crystallization experiments was conducted by adding aqueous Na-ECA solution to aqueous NaCl. In these experiments, the particle sizes decreased to less than 7 µm as the NaCl concentration was increased to >1.2% w/w. The particles yielded by semi-batch crystallization showed improved particle size distributions compared to those obtained by the batch-cooling crystallization method. The solubility of Na-ECA hydrate decreased to less than 10% of that in pure water as the NaCl concentration was increased to 3.0% w/w. This solubility change enabled the production of a highly supersaturated environment, allowing facile generation of microcrystals with a narrow particle size distribution.

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work  

<p>The crystallization mechanism of amino acid derivative <i>t</i>-butoxycarbonyl-L-asparagine (Boc-Asn) was investigated. NMR spectroscopy was used to observe the behavior of Boc-Asn molecules in under- and supersaturated solution. Nuclear Overhauser Effect (NOE) NMR measurements were performed to provide information concerning the intra- or intermolecular access of a particular hydrogen atom to other hydrogen atoms in solution. We compared the interactions identified by NOE measurements for under- and supersaturated solutions of Boc-Asn with those in the crystal, as determined by X-ray analysis. According to the X-ray analysis, intramolecular NOE should not be observed, but intermolecular NOE might be observed between the methyl protons of the <i>t</i>-butoxycarbonyl group and the protons belonging to other functional groups. The time course of the NOE intensity was followed for three solutions with different saturation ratios <i>S</i> (=concentration of solute/solubility). For undersaturated and nearly saturated conditions (<i>S</i>=0.8 and 1.12 at 0°C), the NOE intensity did not change for at least for 250 h. However, for the supersaturated solution (<i>S</i>=1.62 at 10°C), the NOE intensity increased suddenly and rapidly after about 120 h, and no crystals were observed during the NOE measurements. As the observed NOEs agreed with those expected from the arrangement of molecules in the crystal, it was suggested that Boc-Asn molecules aggregated after about 120 h with the same structure as that in the crystal. In addition to the behavior of the Boc-Asn solution before nucleation, we also investigated the effect of aggregation on the crystallization process. Solutions that were preincubated at 10°C for various periods were further cooled and crystallized at −30°C. It was found that when the solution was preincubated under the supersaturated condition for a long time before crystallization, nucleation was enhanced, and consequently, the crystal size distribution became homogeneous.</p>

DOI： 10.1252/jcej.17we027

CiNii Article

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work  

<p>Solvent selection is one of the most important factors for the control of crystal habits. However, this relationship is poorly understood. The aim of this study was to determine the solvent selectivity to obtain a desired crystal habit using <i>tert</i>-butoxycarbonyl-L-asparagine (BocASN) as a model compound. The [110], [100], and [001] faces were dominant for the BocASN crystals obtained from acetone and ethanol. However, the [011], [100], and [001] faces were dominant for those obtained from methanol. The interactions between the solvent molecules and the functional groups exposed on the crystal surface were examined. The solvent-surface interactions on each surface of the BocASN crystal were dependent on the type of solvent. The different solvent-surface interactions along the <i>a</i>-, <i>b</i>-, and <i>c</i>-axes affected the growth rate and aspect ratio of the crystal. The analysis of the solvent-surface interactions is useful to predict the crystal habit.</p>

DOI： 10.1252/jcej.16we140

CiNii Article

Publishing type：Research paper (scientific journal)  

<p>A mL-scale continuous crystallizer has been newly developed to produce small crystals with a narrow size distribution. The crystallizer is composed of a stainless-steel mixing vessel with an inner working volume of 7.9 mL and a high-speed agitator that can agitate the crystallization solution at up to 24,000 rpm. In a previous work, the crystallizer was used for the drowning-out crystallization of glycine and L-alanine. The crystals obtained with the novel crystallizer were small and uniform in size, comparing with those obtained with conventional beaker-scale semi-batch and continuous MSMPR type crystallizers. In this study, the cooling crystallization of L-alanine was attempted using the mL-scale crystallizer. The undersaturated hot solution of L-alanine and the water-immiscible coolant liquid were introduced into the crystallizer and were intensely agitated. The solution was dispersed as small droplets into the coolant liquid and rapidly cooled. The crystals obtained by the mL-scale cooling crystallizer are small and uniform in size as well as the drowning-out crystallization.</p>

DOI： 10.1252/jcej.16we079

CiNii Article

Publishing type：Research paper (scientific journal)  

The batch cooling crystallization of the organic compound, ibuprofen, was carried out under 2.45 GHz microwave irradiation. <i>n</i>-Hexane containing a small amount of acetone (5 mol%) and Fluorinert™, which did not absorb microwave, were selected as the solvent and coolant circulating through the jacket of crystallizer, respectively. The ibuprofen-hexane solution was cooled from 40 to −1°C under microwave irradiation and no irradiation. When the solution was not irradiated to the solution, ibuprofen crystals appeared at 35°C. On the other hand, when irradiation with 300 W microwave was carried out, nucleation did not occur even when the solution temperature reached to −1°C. At that time, the supersaturation ratio was 9.5. Thus, crystal nucleation of ibuprofen was inhibited by the microwave irradiation. The effect of microwave irradiation continued for at least 100 min after the irradiation was stopped at −1°C. By adding a small amount of crystals to the highly supersaturated solution, small crystals with a narrow size distribution were produced.

DOI： 10.1252/jcej.13we189

CiNii Article

Publishing type：Research paper (scientific journal)  

The effect of a seed crystal on nucleation of l-alanine from a quiescent supersaturated solution was investigated. When a seed crystal was not used, nucleation did not occur at least for 5 h. When a seed crystal was introduced into the supersaturated solution with careful attention to avoid convection of the solution, fine crystals appeared at the place far from the seed crystal. At that time, there was no convection at the place that fine crystals appeared. Namely, there was no possibility that those fine crystals came from the surface of seed crystal. We supposed that nucleation was induced by directional diffusion of solute molecules caused by growth of the seed crystal. In order to prove this hypothesis, we designed an experiment using an apparatus composed of two compartments divided by a dialysis membrane that l-alanine molecules could freely permeate. Two supersaturated solutions having a supersaturation ratio of 1.2 and a smaller ratio were placed in the two compartments in the absence of seed crystals. This apparatus allowed the directional diffusion of solute molecules between two solutions. Nucleation occurred within 30 min. The frequency of nucleation among 7-times repeated experiments was in proportion to the difference of supersaturation ratio between the two solutions. This result poses a new mechanism of the secondary nucleation that the directional diffusion caused by growth of existing crystals induces nucleation.

DOI： 10.1016/j.jcrysgro.2012.12.008

Publishing type：Research paper (scientific journal)  

The batch cooling crystallization of an organic compound, p-acetanisidide, was carried out using methanol as a solvent and no seed crystal. The crystallization needed an induction period of 10–200 min before nucleation, and the size distribution of the product crystals was broad with sizes ranging from 10 to 270 µm determined as the diameter of a circle with equal projection area. In order to control the nucleation process and obtain microcrystals with a narrow size distribution, the dissolution of crystals obtained by cooling crystallization, followed by recrystallization was adopted. Thus, the crystals once obtained by cooling crystallization were completely dissolved by heating the slurry to a temperature 17°C that was higher than the saturation temperature by 1.5°C. After the solution was maintained at that temperature for a given time, it was cooled again. In the case of repeated crystallization, the induction period observed in the first crystallization disappeared, and small crystals with a mean diameter of 40 µm and a narrow size distribution were obtained. However, the effect of the complete dissolution of crystals on the production of microcrystals with a narrow size distribution disappeared when the solution was incubated at 17°C over 90 min. These results were explained on the basis of the history of the solution structure.

Publishing type：Research paper (scientific journal)  

A mL-scale continuous crystallizer has been newly developed to produce small crystals with a narrow size distribution. The crystallizer is used for the poor solvent crystallization of glycine and <small>L</small>-alanine. The crystallizer is composed of a stainless-steel mixing vessel with an inner volume of 0.9 mL and a high-speed agitator that can agitate the crystallization solution up to 24,000 rpm. Glycine or <small>L</small>-alanine aqueous solution and poor solvent (methanol) are supplied into the vessel at a constant flow rate and intensely mixed by the agitator. The average residence time was set at 0.33, 3.3 and 33 s by changing the flow rate of an amino acid solution and poor solvent. The crystals obtained by the crystallizer are small and uniform in size, comparing with those obtained by a conventional beaker-scale semi-batch and continuous MSMPR type crystallizers. For example, glycine crystals having the 1/38 of the size of crystals obtained by a semi batch crystallizer were obtained. The short residence time that can be attained by the present mL-scale crystallizer is advantageous for the production of small crystals with a narrow size distribution. The size distribution can be further controlled by changing the mixing ratio of poor solvent.

DOI： 10.1252/jcej.11we158

CiNii Article

Publishing type：Research paper (scientific journal)  

The batch cooling crystallization of an organic compound, <i>p</i>-acetanisidide, was carried out using methanol as a solvent and no seed crystal. The crystallization needed an induction period of 10–200 min before nucleation, and the size distribution of the product crystals was broad with sizes ranging from 10 to 270 µm determined as the diameter of a circle with equal projection area. In order to control the nucleation process and obtain microcrystals with a narrow size distribution, the dissolution of crystals obtained by cooling crystallization, followed by recrystallization was adopted. Thus, the crystals once obtained by cooling crystallization were completely dissolved by heating the slurry to a temperature 17°C that was higher than the saturation temperature by 1.5°C. After the solution was maintained at that temperature for a given time, it was cooled again. In the case of repeated crystallization, the induction period observed in the first crystallization disappeared, and small crystals with a mean diameter of 40 µm and a narrow size distribution were obtained. However, the effect of the complete dissolution of crystals on the production of microcrystals with a narrow size distribution disappeared when the solution was incubated at 17°C over 90 min. These results were explained on the basis of the history of the solution structure.

DOI： 10.1252/jcej.12we131

CiNii Article

Publishing type：Research paper (scientific journal)  

An imidazopyridine derivative developed for osteoporosis treatment (a bone proton pump inhibitor, abbreviated BPPI) was crystallized in two kinds of alcohol. Two crystal polymorphs appeared: an unstable B01 form and a stable B02 form. The B01 form was obtained only from an ethanol solution and was never obtained from a methanol solution. The B02 form was obtained from a methanol solution. In order to understand these different behaviors in the appearance of polymorphs from alcohol, the intra- and inter-molecular interactions of BPPI molecules in solution were analyzed by NMR. As a result, the conformation of BPPI molecules and the structure of molecular aggregates in solution were found to resemble those of the polymorphic crystals that appeared in each alcohol. This result suggests that the control of the conformation of solute molecules is important at first to control the appearing polymorph.

DOI： 10.1252/jcej.08we299

CiNii Article

Publishing type：Research paper (scientific journal)  

The detailed properties of the enzyme from Pseudomonas aeruginosa, which catalyzes the N-acyl linkage between myristic acid and the N-terminal glycine residue of the octapeptide GNAAAARR-NH_2(PKA) in aqueous solution without ATP and CoA, were studied. The substrate specificity for the acyl peptide in the synthetic reaction was examined, and it was found that at least eight amino acid residues are required for the reaction and that the N-terminal glycine residue is not absolutely essential for the reaction because the activity was detected using the octapeptide that has an N-terminal alanine. The activity was also strongly affected by the amino acid sequence because the activity was very weak in the reaction using GARASVLS-NH_2(HIV-1p17^<gag>). The substrate specificity for fatty acids was also examined. In the reactions using lauric acid and decanoic acid, only slight activities were detected; however, those activities were very small compared with the activity in the reaction using myristic acid. In addition, the degradation of myristoyl PKA by the enzyme was detected, although there are only a few reports on demyristoylation. The optimum pH and temperature of the degradation reaction were consistent with those of the synthetic reaction. The degradation reaction was inhibited by divalent cations.

CiNii Article

Publishing type：Research paper (scientific journal)  

The detailed properties of the enzyme from Pseudomonas aeruginosa, which catalyzes the N-acyl linkage between myristic acid and the N-terminal glycine residue of the octapeptide GNAAAARR-NH2 (PKA) in aqueous solution without ATP and CoA, were studied. The substrate specificity for the acyl peptide in the synthetic reaction was examined, and it was found that at least eight amino acid residues are required for the reaction and that the N-terminal glycine residue is not absolutely essential for the reaction because the activity was detected using the octapeptide that has an N-terminal alanine. The activity was also strongly affected by the amino acid sequence because the activity was very weak in the reaction using GARASVLS-NH2 (HIV-1p17(gag)). The substrate specificity for fatty acids was also examined. In the reactions using lauric acid and decanoic acid, only slight activities were detected; however, those activities were very small compared with the activity in the reaction using myristic acid. In addition, the degradation of myristoyl PKA by the enzyme was detected, although there are only a few reports on demyristoylation. The optimum pH and temperature of the degradation reaction were consistent with those of the synthetic reaction. The degradation reaction was inhibited by divalent cations.

DOI： 10.1263/jbb.105.282

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Tubular agglomerates of calcium carbonate crystals (the CC-tubes) were formed from 1 M calcium chloride and 1 M sodium carbonate, and the formation mechanism was investigated. A cylindrical jacketed glass vessel was used as a crystallizer. The newly designed crystallizer was composed of two compartments that were divided by a cation-exchange membrane. The crystallizer was vertically placed and the two solutions were separately placed in each compartment. The CC-tubes were formed in vertical against the surface of the cation-exchange membrane in the upper sodium carbonate solution side. The growth of the CC-tubes was observed through a plane window of the top of the crystallizer by a digital microscope in order to study the growth mechanism of the tubes. In the early stage of crystallization, small cubic crystals appeared on the membrane. Although most parts of the membrane surface were covered with crystals, some small spots on the membrane surface were not covered with crystals. The CC-tubes grew from the uncovered parts. We concluded that the uncovered spots are important for the generation of the CC-tubes. A possible mechanism of the growth of the CC-tubes was proposed.<br>

DOI： 10.2109/jcersj2.116.111

CiNii Article

Publishing type：Research paper (scientific journal)  

DOI： 10.1263/jbb.103.161

Publishing type：Research paper (scientific journal)  

DOI： 10.1021/cg0604576

Publishing type：Research paper (scientific journal)  

The enzyme that catalyzes N-acyl linkage between myristic acid and the NH_2-terminal glycine residue of the octapeptide Gly-Asn-Ala-Ala-Ala-Ala-Arg-Arg-NH_2 in aqueous solution without ATP and coenzyme A was found in Pseudomonas aeruginosa. The enzyme was purified from cellfree crude extract using DEAE-Cellulose, Sephadex G-200, CM-Sephadex C-50, and hydroxyapatite column chromatographies, and then purified approximately 1900-fold with about 1.5% recovery of enzyme activity from the crude extract. Finally, the purified enzyme showed a main band on SDS polyacrylamide gel electrophoresis after staining with Coomassie Brilliant Blue. The band corresponded to a molecular mass of approximately 60 kDa. The K_ms of the purified enzyme for the substrate myristic acid and the octapeptide were 0.36 and 2.6mM, respectively. When myristoyl-CoA instead of myristic acid was used as the substrate for the enzyme reaction, myristoyl octapeptide could be synthesized as observed in the case of myristic acid. The K_m of myristoyl-CoA was 0.17mM.

CiNii Article

Publishing type：Research paper (scientific journal)  

The enzyme that catalyzes N-acyl linkage between myristic acid and the NH2-terminal glycine residue of the octapeptide Gly-Asn-Ala-Ala-Ala-Ala-Arg-Arg-NH2, in aqueous solution without ATP and coenzyme A was found in Pseudomonas aeruginosa. The enzyme was purified from cell-free crude extract using DEAE-Cellulose, Sephadex G-200, CM-Sephadex C-50, and hydroxyapatite column chromatographies, and then purified approximately 1900-fold with about 1.5% recovery of enzyme activity from the crude extract. Finally, the purified enzyme showed a main band on SDS polyacrylamide gel electrophoresis after staining with Coomassie Brilliant Blue. The band corresponded to a molecular mass of approximately 60 kDa. The K(m)s of the purified enzyme for the substrate myristic acid and the octapeptide were 0.36 and 2.6 mM, respectively. When myristoyl-CoA instead of myristic acid was used as the substrate for the enzyme reaction, myristoyl octapeptide could be synthesized as observed in the case of myristic acid. The K-m of myristoyl-CoA was 0.17 mM.

DOI： 10.1263/jbb.102.193

Publishing type：Research paper (scientific journal)  

Cooling crystallization of <I>β</I>-sitosterol that is a kind of phytosterol was carried out, where a water-immiscible solvent hexane containing a ppm level of water was used as a solvent. The initial ratio of water and <I>β</I>-sitosterol concentration adopted in this work was 330/10, 1315/10 and 645/20 ppm/(g/L), which corresponded to 0.51, 2.0, and 0.50 in water/<I>β</I>-sitosterol mole ratio, respectively. When the initial ratio of water and <I>β</I>-sitosterol concentration was 1315/10 ppm/(g/L), thin plate-like crystals were precipitated and were identified as the monohydrate crystals of <I>β</I>-sitosterol. On the other hand, when the initial ratio of water and <I>β</I>-sitosterol concentration was 645/20 ppm/(g/L), needle-like crystals of hemihydrate were precipitated. This result meant that the ppm level of water plays an important role for the pseudo-polymorphism. Since the crystal structure of <I>β</I>-sitosterol hemihydrate had never been reported, we determined it by a single crystal XRD analysis.

DOI： 10.1252/jcej.39.869

CiNii Article

Publishing type：Research paper (scientific journal)  

DOI： 10.1021/cg060045x

Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.jct.2005.07.021

Publishing type：Research paper (scientific journal)  

CiNii Article

Publishing type：Research paper (scientific journal)  

CiNii Article

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Microbial metabolites were screened for inhibitors of hyphal growth in Candida albicans. Inhibitory activity was found among metabolites of a culture of an actinomycete, which had been isolated from soil. The active substance inhibited hyphal growth and induced growth as a chain of yeast cells under hyphal growth induction conditions. The active substance was purified and analyzed with 1H-NMR, 13C-NMR and mass spectra. The substance was identified as valinomycin, and commercial valinomycin inhibited hyphal growth as effectively as the purified metabolite. The effective concentration was from 0.49 to 62.5 microg/ml. Valinomycin also inhibited hyphal growth in other dimorphic fungi, Candida tropicalis and Aureobasidium pullulans. These results suggest that valinomycin may be a useful tool for understanding the morphological transition of dimorphic fungi.

CiNii Article

Publishing type：Research paper (scientific journal)  

Saccharomyces cerevisiae has the potential for morphological differentiation. In order to positively utilize the morphological transition of S. cerevisiae for the separation of cells from culture broth, the cell settling of mutant J19 having pseudohyphal form was examined. Mutant cells settled faster in stationary test tubes than those of the parental strain having yeast-like form. Furthermore, in an attempt to establish a basis for manipulation of the morphological transition between the yeast-like and pseudohyphal forms, a plasmid harboring the SCL1 gene under the control of the GAL1 promoter was constructed. The SCL1 gene complements the morphological phenotype of mutant J19. The plasmid was transformed into mutant J19, and the morphological transition of the transformant by changes in carbon source was examined. It was found that partial manipulation of the morphological transition was possible.

DOI： 10.1016/j.bej.2005.07.001

Publishing type：Research paper (scientific journal)  

Microbial metabolites were screened for inhibitors of hyphal growth in Candida albicans. Inhibitory activity was found among metabolites of a culture of an actinomycete, which had been isolated from soil. The active substance inhibited hyphal growth and induced growth as a chain of yeast cells under hyphal growth induction conditions. The active substance was purified and analyzed with 1H-NMR, 13C-NMR and mass spectra. The substance was identified as valinomycin, and commercial valinomycin inhibited hyphal growth as effectively as the purified metabolite. The effective concentration was from 0.49 to 62.5 μg/ml. Valinomycin also inhibited hyphal growth in other dimorphic fungi, Candida tropicalis and Aureobasidium pullulans. These results suggest that valinomycin may be a useful tool for understanding the morphological transition of dimorphic fungi. © Japan Antibiotics Research Association.

DOI： 10.1038/ja.2005.102

PubMed

Publishing type：Research paper (scientific journal)  

Most proteins involved in the synthesis of the GPI core structure of Saccharomyces cerevisiae are essential for growth. To explore the relationship between the GPI anchor structure and β-1,6-glucan synthesis, we screened deletion mutants in genes involved in GPI synthesis for osmotic remedial growth. Heterozygous diploid strains were dissected on medium with osmotic support and slow growth of the mcd4 deletion mutant was observed. The mcd4 mutant showed abnormal morphology and cell aggregation, and was hypersensitive to SDS, hygromycin B and K1 killer toxin. Incorporation of GPI cell wall proteins was examined using a GPI-Flo1 fusion protein. The result suggested that the mcd4 deletion causes a decrease in GPI cell wall proteins levels. The mutation also caused a decrease in mannan levels and an increase in alkali-insoluble β-1,6-glucan and chitin levels in the cell wall.

CiNii Article

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work  

Staining with calcofluor white (CFW), which is known to bind chitin-rich areas of the cell wall, revealed a difference in the fluorescence intensity at the hyphal tip between <I>Candida albicans</I> hyphal cells that were grown in modified Lee (M-Lee) and SPG media. The fluorescence intensity at the tip increased with the addition of salts and sugar to SPG. The chitin levels per dry cell weight in cells grown in modified Lee and SPG with 1.0 <small>M</small> NaCl were also higher than in SPG. These results suggest that chitin synthesis at the tip of <I>C. albicans</I> might be activated by the addition of salts and sugar to a medium.

DOI： 10.1271/bbb.69.1798

CiNii Article

Publishing type：Research paper (scientific journal)  

The effects of seven kinds of impurities on the solvent-mediated transformation of crystal polymorphs of a drug substance AE1-923 were investigated. AE1-923 was developed for an indication of pollakiuria and pain. It has three polymorphs, namely the unstable A-form, the metastable B-form and the stable C-form. The impurities tested were the starting compounds, the reaction reagents and the intermediates in the synthesis of AE1-923. One of the impurities, an intermediate AE1-923ME (methylester of AE1-923), inhibited the solvent-mediated polymorph transformation of the B-form to the C-form, although the transformation of the A-form to the B-form was not inhibited. The other impurities had no effect on the two steps of polymorph transformation. The inhibitory effect of AE1-923ME that was evaluated by the overall transformation rate constant kc exponentially increased with an increase in the concentration of AE1-923ME. AE1-923ME of 0.5 wt% completely suppressed the nucleation of the stable C-form crystals. However, crystal growth of the C-form was not inhibited.

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work  

Crystallization of p-acetanisidide (PAC) was carried out in the presence of p-acetoacetanisidide (APAC) as a solute analogue impurity. Addition of APAC into the supersaturated solution of PAC did not affect the structure of crystals of PAC, but affected the nucleation and crystal growth and also the morphology (crystal shape) of PAC crystals. APAC made the induction period before the beginning of precipitation of PAC crystals longer. The growth rate of PAC crystals was decreased. In particular, the growth of 11001 surface was inhibited, resulting in the change of the crystal shape from plate-like to rod-like. Hydrogen bonding between PAC and APAC in solution was observed by analyzing the chemical shift of N-H hydrogen. As a result, the effects of APAC on the crystallization of PAC could be explained in terms of the hydrogen bonding between PAC and APAC molecules.

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

The control of crystal polymorphs was investigated using a WWDJ batch crystallizer and glycine as a model compound. The WWDJ batch crystallizer is a newly developed crystallizer, which is equipped with a slurry sprinkler named Wall Wetter fixed on the shaft of an impeller and a double‐deck jacket. When a conventional crystallizer was used, the unstable α‐form crystals were always obtained. However, when the WWDJ batch crystallizer was used, the stable γ‐form crystals were obtained. The appearance of different polymorphs depends on the cooling rate during the crystallization. The γ‐form crystals were obtained by slow cooling, while the α‐form was obtained by rapid cooling. It means that the solvent‐mediated transformation of glycine crystal polymorphs can be controlled by changing the cooling rate in the WWDJ crystallizer. These results were obtained due to the fact that the WWDJ batch crystallizer accelerates the dissolution of metastable crystals and the growth of stable crystals.

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work  

The aggregation behavior of solute molecules in under- and supersaturated solutions was investigated using an organic compound p-acetanisidide (PAC) as a model compound and NMR method. The aggregation behavior was discussed by comparing the structure of aggregates with that of a single crystal determined by X-ray crystallographic analysis. And also, the relationship between the aggregation and the nucleation was discussed. PAC molecules were found in aggregates before nucleation, not only in the super-saturated solution but also in the under-saturated solution. The growth of aggregates in the under-saturated solution was slower than that in the super-saturated solution. The local structures observed in the aggregates were intermolecular hydrogen bonding between N-H hydrogen and C=O oxygen, and the intra- and intermolecular access of methoxy group hydrogen to (orto-) hydrogen on a benzene ring within a distance of 4 Å. These interactions were also observed between adjacent PAC molecules in crystal. The whole structure of aggregates, however, was not the same as that of the crystal. The formation of aggregates before nucleation in the under-saturation condition suppressed the nucleation, and the formation of aggregates in the super-saturation condition accelerated the nucleation.

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work  

The kinetics of the dissolution of l-aspartic acid crystals under the gentle and vigorous agitation was investigated. A dissolution rate equation was derived by assuming two steps: the disintegration of molecules from the surface of crystals and the mass transfer of disintegrated molecules into the bulk solution. An intrinsic expression of the relationship between the solute concentration of the bulk solution and the dissolution time was also derived. The dissolution process of monodisperse and polydisperse crystals of l-aspartic acid was well estimated, and the change of crystal size distribution of polydisperse crystals during dissolution was simulated with good accuracy.

DOI： 10.1016/S1385-8947(01)00259-5

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work  

A novel batch crystallizer has been developed and used for the crystallization of l-aspartic acid, resulting in large product crystals with a narrow crystal size distribution.

The batch crystallizer was equipped with a slurry sprinkler fixed on the shaft of an impeller, and a double-deck jacket. The slurry sprinkler, known as Wall Wetter, is specially designed for agitating the slurry and sprinkling it on the wall of the crystallizer headspace which is covered by the upper jacket. It was expected that by setting the upper jacket temperature at an appropriate high temperature, fine crystals could be dissolved during the fall of slurry along the wall, and consequently the crystal size distribution would shift to the large side. l-aspartic acid was chosen as an example to demonstrate this process. l-aspartic acid was crystallized at an initial supersaturation ratio (C/Cs) of 1.7 with no seeds. The classification exponent n and characteristic size De of product crystals, which were evaluated by the Rosin Rammler Sperling Bennet (RRSB) distribution function, were 3.9 and 302 μm, respectively, compared with 2.2 and 237 μm, respectively, in a control crystallization experiment not using the Wall Wetter.

DOI： 10.1016/S1385-8947(01)00153-X

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work  

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work  

Using a newly developed batch crystallizer (WWDJ-crystallizer) equipped with a slurry sprinkler named Wall Wetter and a double-deck jacket, a suppression of the solvent-mediated transformation of the metastable polymorphic crystals was attempted. Crystallization of l-glutamic acid was carried out to show an example of the suppression. The target polymorphic crystals, namely the metastable α-form crystals were exclusively obtained from the aqueous solution without transformation to the stable β-form polymorph even at a temperature where the transformation could not be avoided if a conventional batch crystallizer was used. The characteristic size of crystals obtained by WWDJ-crystallizer was large and their size distribution was narrow, comparing with those obtained by a conventional crystallizer.

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work  

The light distribution in the externally illuminated cylindrical photo-bioreactor for production of hydrogen by a photosynthetic bacterium Rhodobacter capsulatus ST-410 was estimated. The estimation was performed on the basis of the Matsuura and Smith’s diffuse model [1]. In the diffuse model, the incident light rays are assumed to proceed in every direction and the local intensity is calculated as the sum of the intensities of light. Since Lambert–Beer’s law, extensively used in photometry, was not useful for explaining the decrease in the intensity of light by the biomass, an empirical expression was used. The measurement of the intensities from every direction was conducted in an externally illuminated cylindrical photo-bioreactor having an inner diameter of 60 mm and a working volume of 550 ml. The obtained results confirmed our estimation. The light distribution was applied to estimate the hydrogen production by R. capsulatus ST-410 using the same photo-bioreactor. The overall hydrogen-production rate was successfully estimated.

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work  

We examined cadmium removal from aqueous solution using the moss Pohlia flexuosa. The amounts of cadmium ions removed increased with increasing initial concentration of the ion over the range from 10 to 100 μg/ml. The concentration factor, which is an indicator of the ability to remove heavy metals, was 770 ml/g of dry moss at 10 μg/ml of CdCl2. We examined the effects of temperature, respiratory inhibitors, and pH on the cadmium removal from 30 and 100 μg/ml CdCl2 solution. The results suggested that cadmium removal at these concentrations may be mainly dependent on physical adsorption on the cell surface. The carboxyl groups of the moss were modified by the HCl/methanol esterification method. The modified moss showed almost no cadmium ions removal. Carboxyl groups on the cell surface may markedly contribute to the adsorption. We discussed the process of cadmium removal from solution using the moss in comparison with the process of mercury removal, which was reported previously.

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work  

The initial stage of crystallization of hen-egg-white lysozyme was investigated. Lysozyme molecules formed a structure just after the supersaturated solution was prepared. The structure could be understood as changes in solution three-dimensional structure induced by attractive interactions or aggregates with an average size of 6.5 nm. The structure formation, however, did not immediately link to crystal growth. An induction period was needed before the start of crystal growth. DSC analysis of the supersaturated solution revealed that the structure thus formed at the beginning of crystallization is transformed just before the end of the induction period. DSC analysis also revealed that the driving force of the transformation is the formation of hydrophobic bonds between lysozyme molecules. Our understanding of the behavior of lysozyme molecules before crystal growth was furthered by measurement of the ζ-potential of the aggregates. Based on the present results, a possible model of the early stage of crystal growth of lysozyme was proposed.

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work  

Mechanism of crystal growth of thermolysin was investigated through a thermal measurement by differential scanning calorimetry (DSC) of a crystal suspension which is under the progress of crystallization. The DSC curve obtained for the crystal suspension indicates that there are at least three groups of thermolysin differing in the thermal stability. The presence of the three groups is consistent with the two step mechanism of crystal growth of thermolysin previously proposed: the crystallization of thermolysin proceeds through two steps; the first step is the formation of primary particles with 20 nm in diameter; and the second step is the crystal growth by highly ordered aggregation of the primary particles. In the DSC curve, Peak 1 (the denaturation temperature: 74.5-75.0 °C), Peak 2 (85.5-87.0 °C) and Peak 3 (95.5 °C) are assigned to the denaturation of monomers, primary particles (oligomers), and crystals, respectively.

Presentation type：Poster presentation  

Venue：University of Strathclyde, Glasgow, Scotland  

Presentation type：Oral presentation (general)  

Venue：東京農工大学  

Presentation type：Oral presentation (invited, special)  

Venue：信州大学  

Presentation type：Oral presentation (general)  

Venue：信州大学  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Poster presentation  

Presentation type：Oral presentation (general)  

Presentation type：Poster presentation  

Presentation type：Oral presentation (invited, special)  

Presentation type：Poster presentation  

Presentation type：Oral presentation (invited, special)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)