Novel chelate-setting calcium-phosphate cements fabricated with wet-synthesized hydroxyapatite powder

The hydroxyapatite (HAp) powder preparation process was optimized to fabricate inositol phosphate-HAp (IP6-HAp) cement with enhanced mechanical properties. Starting HAp powders were synthesized via a wet chemical process. The effect of the powder preparation process on the morphology, crystallinity, median particle size, and specific surface area (SSA) of the cement powders was examined, together with the mechanical properties of the resulting cement specimens. The smallest crystallite and median particle sizes, and the highest SSA were obtained from ball-milling of as-synthesized HAp powder under wet conditions and then freeze-drying. IP6-HAp cement fabricated with this powder had a maximum compressive strength of 23.1 ± 2.1 MPa. In vivo histological studies using rabbit models revealed that the IP6-HAp cements were directly in contact with newly formed and host bones. Thus, the present chelate-setting HAp cement is promising for application as a novel paste-like artificial bone.     

A novel polysaccharide involved in the pellicle formation of Acetobacter aceti

Acetobacter aceti IFO 3284 has been shown to have two types of strains: one forms a smooth-surfaced colony (S strain) and the other forms a rough-surfaced colony (R strain) (Matsushita et al., 1992). In this study, both S and R strains were isolated and characterized. The S strain grew well in submerged culture but very poorly in static culture. In contrast, the R strain grew well in static culture by floating on the surface of the culture medium, as well as in shaking submerged culture. Scanning electron microscopy revealed that the R strain was covered by some amorphous materials that were not seen in the S strain. The R strain produced 5-fold higher levels of sugars related to polysaccharides responsible for pellicle formation than the S strain did. Unlike cellulose of Acetobacter xylinum, the polysaccharides of the R strain were cellulase-resistant and alkaline-sensitive. The polysaccharides were not secreted into the culture medium, and more than 90% of them were retained in the membrane fraction when the cells were disrupted under mild conditions by lysozyme treatment. Furthermore, the polysaccharides were shown to be mainly attached to the outer membrane when separated. After solubilization with beta-octylglucoside, the membrane-attached polysaccharides were purified by several steps including enzyme treatment, column chromatography and alcohol precipitation. The purified polysaccharide was estimated to have an apparent molecular mass of 700-kDa based on Sephacryl S-500 column chromatography, and to be composed of two monosaccharides, glucose and rhamnose, at an approximately equimolar ratio. Thus, in this study, we clarified that the A. aceti R strain produced a polysaccharide associated with the flotation of the cells on the medium surface, like A. xylinum, and that the polysaccharide was a novel one consisting of glucose and rhamnose.     

Deposition of Metal Oxide Films from Metal–EDTA Complexes by Flame Spray Technique

R₂O₃ (R = Y, Eu, Er) metal oxides were synthesized from metal–ethylenediaminetetraacetic acid (EDTA) complexes using a flame spray technique. As this technique enables high deposition rates, films with thickness of several tens of micrometers were obtained. Films of yttria, europia, and erbia phase were synthesized on stainless-steel substrates with reaction assistance by H₂–O₂ combustion gas. The oxide films consisted of the desired crystalline phase with micropores. The porosity of the films was in the range of 6–15%, varying with the metal used. These results suggest that the true density of the metal oxide obtained from metal–EDTA powder through the thermal reaction process plays an important role in achieving film with the desired porosity.     

Purification and characterisation of two extracellular acid proteinases from Monascus pilosus

Genus Monascus is one of the most important microorganisms in the fermentation industry in Asia. However, only a little attention has been paid to the proteinases produced by this fungus and their role in the fermentation process. The main objective of this study was to purify and characterise acid proteinases produced by Monascus pilosus. Two acid proteinases (MpiAP1 and MpiAP2) were purified to homogeneity. Both purified enzymes, MpiAP1 and MpiAP2, were monomeric structures with molecular masses of around 43 and 58 kDa, respectively. The former was an acidic non-glycoprotein, whereas the latter was an acidic glycoprotein with 27% carbohydrate content. Although amino-terminal amino acid sequence analysis of both enzymes (MpiAP1 and MpiAP2) of 20 amino acid length showed over 90% similarity, their amino-terminal amino acids were different from each other. Both enzymes were optimally active at 55 °C and at pH 2.5–3.0 against casein or human haemoglobin. The T_1/2 values of MpiAP1 and MpiAP2 were 65 and 70 °C, respectively. Both of the enzymes were completely inhibited by pepstatin A, and markedly by SDS. MoO₃ also showed a partial inhibition of both enzymes. Milk casein and haemoglobin were good substrates for these enzymes. Eleven cleavages were detected using the oxidised insulin B-chain as a peptide for the proteolytic specificity test of MpiAP1, while seven cleavages were detected for MpiAP2.     

Formaldehyde elimination with formaldehyde and formate oxidase in membrane of acetic acid bacteria

Formaldehyde elimination was successfully carried out with Acetobacter sp. SKU 14, having strong formaldehyde-oxidizing activity in the cytoplasmic membrane. Formaldehyde was decomposed via formate to carbon dioxide by formaldehyde- and formate-oxidizing activities. A resting-cell suspension of the organism was more convenient for practical purposes than the isolated membrane fraction. In Gluconobacter suboxydans IFO 12528, formaldehyde elimination was not so prominent when compared with that in Acetobacter sp. SKU 14.     

A firm as a knowledge-creating entity: a new perspective on the theory of the firm

The knowledge-based view of the firm views a firm as a knowledge-creatingentity, and argues that knowledge and the capability to createand utilize such knowledge are the most important source ofa firm's sustainable competitive advantage. Knowledge and skillsgive a firm a competitive advantage because it is through thisset of knowledge and skills that a firm is able to innovatenew products/processes/services, or improve existing ones moreefficiently and/or effectively. The raison d'être of afirm is to continuously create knowledge.     

Acetylated Xylan Degradation by Glycoside Hydrolase Family 10 and 11 Xylanases from the White-rot Fungus Phanerochaete chrysosporium

Endo-type xylanases are key enzymes in microbial xylanolytic systems, and xylanases belonging to glycoside hydrolase (GH) families 10 or 11 are the major enzymes degrading xylan in nature. These enzymes have typically been characterized using xylan prepared by alkaline extraction, which removes acetyl sidechains from the substrate, and thus the effect of acetyl groups on xylan degradation remains unclear. Here, we compare the ability of GH10 and 11 xylanases, PcXyn10A and PcXyn11B, from the white-rot basidiomycete Phanerochaete chrysosporium to degrade acetylated and deacetylated xylan from various plants. Product quantification revealed that PcXyn10A effectively degraded both acetylated xylan extracted from Arabidopsis thaliana and the deacetylated xylan obtained by alkaline treatment, generating xylooligosaccharides. In contrast, PcXyn11B showed limited activity towards acetyl xylan, but showed significantly increased activity after deacetylation of the xylan. Polysaccharide analysis using carbohydrate gel electrophoresis showed that PcXyn11B generated a broad range of products from native acetylated xylans extracted from birch wood and rice straw, including large residual xylooligosaccharides, while non-acetylated xylan from Japanese cedar was readily degraded into xylooligosaccharides. These results suggest that the degradability of native xylan by GH11 xylanases is highly dependent on the extent of acetyl group substitution. Analysis of 31 fungal genomes in the Carbohydrate-Active enZymes database indicated that the presence of GH11 xylanases is correlated to that of carbohydrate esterase (CE) family 1 acetyl xylan esterases (AXEs), while this is not the case for GH10 xylanases. These findings may imply co-evolution of GH11 xylanases and CE1 AXEs.