Analysis of Transglucosylation Products of Aspergillus niger α-Glucosidase that Catalyzes the Formation of α-1,2- and α-1,3-Linked Oligosaccharides

According to whole-genome sequencing, Aspergillus niger produces multiple enzymes of glycoside hydrolases (GH) 31. Here we focus on a GH31 α-glucosidase, AgdB, from A. niger . AgdB has also previously been reported as being expressed in the yeast species, Pichia pastoris ; while the recombinant enzyme (rAgdB) has been shown to catalyze tranglycosylation via a complex mechanism. We constructed an expression system for A. niger AgdB using Aspergillus nidulans . To better elucidate the complicated mechanism employed by AgdB for transglucosylation, we also established a method to quantify glucosidic linkages in the transglucosylation products using 2D NMR spectroscopy. Results from the enzyme activity analysis indicated that the optimum temperature was 65 °C and optimum pH range was 6.0–7.0. Further, the NMR results showed that when maltose or maltopentaose served as the substrate, α-1,2-, α-1,3-, and small amount of α-1,1-β-linked oligosaccharides are present throughout the transglucosylation products of AgdB. These results suggest that AgdB is an α-glucosidase that serves as a transglucosylase capable of effectively producing oligosaccharides with α-1,2-, α-1,3-glucosidic linkages.     

Proposal of cause–effect pattern library for realizing sustainable businesses

Sustainable business design has gained growing interest in recent years. However, it is often difficult to clarify which business activities actually contribute to (or violate) the sustainability of the earth due to high complexity of environmental and economical system of our society. In order to help a business to generate sustainable business ideas handling this complexity in a systematic and comprehensive manner, this paper proposes a method to formulate a wide variety of causalities in our society into a cause–effect pattern library and illustrates how to use it for design and planning of sustainable businesses.     

Formation of Tetravalent Fe Ions in LaFeO3 Perovskite Through Mechanochemical Modification by Ball Milling

Mechanochemical modification of previously synthesized LaFeO₃ perovskite‐type oxide by a high‐energy ball milling was investigated to introduce Fe⁴⁺ ions or transform some Fe³⁺ into Fe⁴⁺ in LaFeO₃. X‐ray absorption fine structure studies revealed that the formation of Fe⁴⁺ ions into LaFeO₃ perovskite has been achieved at first time by ball milling at room temperature without any additives or replacement of La³⁺ ions by some divalent cations. The structural model of Fe⁴⁺ containing LaFeO₃ could be described as with a modified perovskite having equal amounts of La and Fe vacancies, which is supported by a good correlation between the results of Fe K‐edge XANES spectra and O₂‐TPD. The synthesis of Fe⁴⁺‐containing LaFeO₃ perovskite by ball milling was able to produce the O₂ adsorption capacity of nonsubstituted perovskite‐type oxide.     

A Single Mutation at the Ferredoxin Binding Site of P450 Vdh Enables Efficient Biocatalytic Production of 25‐Hydroxyvitamin D3

Vitamin D₃ hydroxylase (Vdh) from Pseudonocardia autotrophica is a cytochrome P450 monooxygenase that catalyzes the two‐step hydroxylation of vitamin D₃ (VD₃) to produce 25‐hydroxyvitamin D₃ (25(OH)VD₃) and 1α,25‐dihydroxyvitamin D₃ (1α,25(OH)₂VD₃). These hydroxylated forms of VD₃ are useful as pharmaceuticals for the treatment of conditions associated with VD₃ deficiency and VD₃ metabolic disorder. Herein, we describe the creation of a highly active T107A mutant of Vdh by engineering the putative ferredoxin‐binding site. Crystallographic and kinetic analyses indicate that the T107A mutation results in conformational change from an open to a closed state, thereby increasing the binding affinity with ferredoxin. We also report the efficient biocatalytic synthesis of 25(OH)VD₃, a promising intermediate for the synthesis of various hydroxylated VD₃ derivatives, by using nisin‐treated Rhodococcus erythropolis cells containing Vdh_T107A. The gene‐expression cassette encoding Bacillus megaterium glucose dehydrogenase‐IV was inserted into the R. erythropolis chromosome and expressed to avoid exhaustion of NADH in a cytoplasm during bioconversion. As a result, approximately 573 μg mL^?1 25(OH)VD₃ was successfully produced by a 2 h bioconversion.     

Transparent Hydroxyapatite Prepared by Hot Isostatic Pressing of Filter Cake

Hydroxyapatite powder was synthesized and formed into a compact in an aqueous medium using a filter-cake method. The compact was hot isostatically pressed at 700° to 1000°C and 100 MPa for 2 h. Fully dense, transparent materials were obtained above 800°C. Both forming and densification methods were found to be important in obtaining transparent materials.     

Direct observation of internal structure in spray-dried yttria-doped zirconia granule

Spray-dried yttria-doped zirconia granules were made transparent by immersion in a liquid and the internal structure was characterized using an optical microscope. This unique technique was found to be applicable for this system by using an immersion liquid with appropriate refractive index, and it enabled observation of the internal structure to be made over the entire volume of granules, in clear contrast to conventional SEM observation. Distinct features, which were considered to be agglomerates, were found in the granules. This was supported by SEM observation.     

Adsorption and photocatalytic decomposition of methylene blue on mesoporous metallosilicates

Mesoporous silica and mesoporous metallosilicates with Al, Ti and Fe as foreign metal species were successfully synthesized by the rapid room temperature method. Mesoporous metallosilicates with low contents of foreign metals possessed high surface area (S_a), large mesopore volume (V_mp) and highly ordered hexagonal mesoporous structure. Increases in foreign metal contents caused disordering the mesoporous structures and lowering the S_a and V_mp values. Bleaching of aqueous methylene blue (MB) by mesoporous silica and metallosilicates was investigated. Mesoporous aluminosilicate and ferrosilicate with cation-exchangeable ability showed the excellent property for the adsorption of MB of cationic dye, while mesoporous ferrosilicate and titanosilicate which absorbed UV lights catalyzed the photocatalytic decomposition of MB under UV-illumination.