Purification and enzymatic properties of the extracellular and constitutive chitosanase produced by Bacillus subtilis RKY3

BACKGROUND: Purification and enzymatic properties of a chitosanase from Bacillus subtilis RKY3 have been investigated to produce a chitooligosaccharide. The enzyme reported was extracellular and constitutive, which was purified by two sequential steps including ammonium sulfate precipitation and ion exchange chromatography. RESULTS: Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis of the purified chitosanase revealed one single band corresponding to a molecular weight of around 24 kDa. The highest chitosanase activity was found to be at pH 6.0 and at 60 °C. Although the mercaptide forming agents such as Hg²⁺ (10 mmol L^?1) and p‐hydroxymercuribenzoic acid (1 mmol L^?1, 10 mmol L^?1) significantly or totally inhibited the enzyme activity, its activity was enhanced by the presence of 10 mmol L^?1 Mn²⁺. The enzyme showed activity for hydrolysis of soluble chitosan and glycol chitosan, but colloidal chitin, carboxymethyl cellulose, crystalline cellulose, and soluble starch were not hydrolyzed. The analysis of chitosan hydrolysis by thin‐layer chromatography and viscosity variation revealed that the purified enzyme should be endosplitting‐type chitosanase. CONCLUSION: The chitosanase produced by Bacillus subtilis RKY3 was a novel chitosanlytic enzyme with relatively low molecular weight, which is a versatile enzyme for chitosan hydrolysis because it could hydrolyze soluble chitosan into a biofunctional oligosaccharide at a high level. Copyright © 2011 Society of Chemical Industry     

Conceptual modeling of causal map: Object oriented causal map

This study has been started from question “Is there a methodology that can make causal map comprised of causality as a database by using conceptual modeling method?” In this research, causal map is proposed to represent causal relation by using conceptual modeling method. Therefore, we formalize causality as a cognitive rule to allow us to control changes in the decision making environment. Such causality is embedded in the real world (application domain). And, user (decision maker) use to represent set of causality which decision-makers have retrieved from the set of knowledge or experiences in application domain. Such set of causality that decision-makers possess in their know–how and short (long) term memory are usually formalized by causal map. It is verified for users whether this causal map is helpful in solving their problems. By extending the basis of conceptual modeling theory (ontology theory, classification theory, decomposition theory, and semantic network theory), we introduce a concept of causal entity diagram and address why causal map is needed to analyze a specific domain knowledge for given decision problem solving. Finally, object oriented causal map (O2CM) were employed to verify usefulness of causal map for user (decision maker) in this study.     

Increased quality and functionality of kimchi when fermented in Korean earthenware (onggi)

Kimchi was fermented in onggi and other containers at 4 °C for 4 weeks. Two types of onggi were used: glazed and nonglazed onggi. Other containers such as polyethylene plastic containers, polypropylene containers for use in a kimchi refrigerator, stainless steel and glass bottles were used. During the fermentation, kimchi fermented in onggi showed relatively stable acidity change compared with those in the other containers. Also it showed higher lactic acid bacteria multiplication (10⁸–10⁹ cfu g^?1 at 4th week) but slower general aerobic bacteria multiplication than the others. The springiness of kimchi fermented in onggi was more than 50% at 4th week, it is higher than the others. Its carbonic acid taste and overall acceptability were excellent in sensory evaluations. The antioxidative and cancer‐cell antiproliferative activities were also greater in kimchi fermented in onggi than the others. Between the two types of onggi, nonglazed onggi showed better results in both properties and functionalities of kimchi. Onggi showed higher gas permeability than polyethylene plastic containers and glass bottles because of its porous structure, and lactic acid bacteria could have benefited from this condition. It possibly contributes to optimal ripening of kimchi resulting in better properties, especially texture and taste, and health functionalities.     

Immobilization of DNA on nano-hydroxyapatite and their interaction with carbon nanotubes

Here we present a preliminary study on the interaction of bio-molecules (deoxyribonucleic acid (DNA) and nano-hydroxyapatite (HA)) with multi-wall carbon nanotubes (MWCNTs). Initially, nano-size hydroxyapatite was interacted with functionalized carbon nanotubes (FCNTs, HFCNTs) and then 100 base pair (bp) DNA was immobilized (DHFCNTs). Well-known acid treatment was used to functionalize the MWCNTs. The characteristic vibrational and stretching modes of hydroxyl and carbonyl group were observed at 3401, 1632 and 1708 cm^?1, validating fucntionalization. The existence of ³¹P and ¹H signals were measured by the solid state NMR spectroscopy for HA, HFCNTs and DHFCNTs which revealed the chemical interaction between HA powder and FCNTs. Appearance of an N 1s peak in the photoelectron spectra indicated the covalent attachment. Band deterioration is observed from slab gel-electrophoresis studies. Electrophoretic time study indicated that 20 min is required to run the DNA in column.     

Cytotoxic Petrosiacetylenes from the Marine Sponge Petrosia sp.

A novel petrosiacetylene analog (petrosiacetylene E) has been isolated from the Korean marine sponge Petrosia sp., along with petrosiacetylene A, B and C. Their structures were elucidated on the basis of spectroscopic methods and the stereochemistry of the new compound was determined by using the modified Mosher’s method. Petrosiacetylene E showed higher cytotoxicity against five human cancer cell lines than petrosiacetylene A and B, presumably due to the additional hydroxy group located at C-16.     

Correlation of Microstructure and Hydrogen Delayed Fracture for 1GPa Steels

Automobile industry tries to reduce the weight of automobile using high-strength steels.However,the high-strength steels are highly susceptible to delayed-fracture caused by hydrogen embrittlement.With increasing the strength,hydrogen embrittlement is more sensitive to diffusible hydrogen.The mechanism of delayed-fracture and the relationship with the microstructure and alloying elements are still ambiguous.This study analyzed the effect of the size and the spheroidization rate for the carbides on hydrogen-induced delayed fracture for 1GPa TS steel.     

Open‐Ended Waveguide Antenna Using a Single Split‐Ring Resonator

This letter proposes an open‐ended waveguide antenna with a single split‐ring resonator. In contrast to the waveguide antennas incorporating multiple rings reported in a previous study, which exhibited narrow bandwidth, the proposed antenna uses only one ring to achieve broader bandwidth while keeping the aperture small. A single ring has a relatively low quality factor compared to multiple rings. The simulated and measured fractional bandwidth was 4.13% and 4.03%, respectively, which is much broader than the fractional bandwidth of about 1% demonstrated in a previous study. This simple technique can be used in many applications that require small apertures including near‐field probes and array elements.     

Characterization of electromagnetic properties for durability performance and saturation in hardened cement mortar

Electromagnetic (EM) properties—dielectric constant and conductivity are changed with porosity and saturation in cement-based materials. In this paper, dielectric constant and conductivity are measured in cement mortar with 5 different mixture conditions considering saturation. For the same mixture proportions, durability tests including porosity, chloride diffusion, air permeability, sorptivity, and water diffusion are performed. Among the continuously measured EM properties within 5–20 GHz of frequency range for different saturation, results under 60% of saturation which shows stable results are selected and averaged as one value. The averaged measurements utilizing results under 60% of saturation are compared with those from durability tests.Through the normalization using the results of W/C 40% which shows best durability performances, changing ratios of durability characteristics are evaluated with normalized dielectric constant and conductivity. The behaviors of EM properties with different saturation and their relationships with durability performances are studied.     

Mechanical properties and durability of PMMA impregnated mortar

Polymer impregnated concrete (PIC) is known to exhibit better strength and durability characteristics than the other classes of polymer cement composites. In the work described herein the monomer was impregnated into cement mortar and polymerized by two methods — the conventional thermal method and using microwaves. The mechanical properties and durability characteristics of the samples and on exposure to chemical environments were then evaluated. The above studies revealed that the strengths of PIC specimens were almost 2–3 times better than those of conventional cement mortars. The chemical resistance was also found to be superior even on prolonged exposure to the chemical media. This may be attributed to the protective layer formed by the polymer on the cement mortar, which prevents the external chemical media from interacting with the cement particles. The properties of the PIC specimens prepared by both methods have also been compared and discussed in this paper.