Hataichanoke Niamsup

Rapid detection of myrosinase-producing fungi: a plate method based on opaque barium sulphate formation

A simple and rapid technique to assess the capability of fungi to produce myrosinase is reported. This was carried out by growing the tested fungi in sinigrin–barium agar plates. Strains capable of producing myrosinase were indicated by an opaque barium sulphate zone forming underneath and/or surrounding their colonies. This simple test has been confirmed by determination of myrosinase activity in liquid culture. In positive isolates, enzyme acitivity was detected in cell-free extracts, not in culture filtrates. In the case of non-myrosinase-producing strains, no opaque zone was observed and the enzyme was not detected either in cell-free extracts or in culture filtrates.

Screening of filamentous fungi for production of myrosinase

A linhagem Aspergillus sp. NR46FB, isolada de solo atraves da tecnica do agar sulfato de bario-sinigrina, foi testada quanto a producao de mirosinase. O fungo degradou completamente o glicosinolato e produziu 3,19 U.mL-1 de mirosinase, apos 48 h de cultivo. Devido a alta producao de mirosinase, esse novo isolado e um potente candidato para aplicacoes industriais.

Evaluation of Sample Preparation Methods from Rice Seeds and Seedlings Suitable for Two-Dimensional Gel Electrophoresis

In a proteomic study, sample preparation is very important because it affects the quality of protein profiles on two-dimensional gel electrophoresis (2-DE). This study investigated the suitability of four protein extraction methods—direct lysis buffer extraction, trichloroacetic acid (TCA)/acetone precipitation, phenol extraction, and polyethylene glycol (PEG) fractionation—from rice seeds and seedlings (Oryza sativa L. ssp. indica cv. Khao Dawk Mali 105). The effectiveness of these methods was evaluated by the protein quantity and the 2-DE profiling quality. This included the number of protein spots, the consistency and uniqueness of protein spots, and their distribution in different ranges of pI and molecular weight (Mr). For protein quantity, the phenol and direct lysis extraction methods gave the highest protein yield in rice seeds and rice seedlings, respectively. However, in terms of the quality of 2-DE profiles, samples prepared by the TCA/acetone and phenol methods exhibited higher protein resolution and more spots than the protein profile derived from direct lysis extract. In addition, TCA/acetone method had the efficiency for high Mr protein detection. PEG fractionation provided the best 2-DE pattern in terms of resolution, number of spots, minimal streaking, and reproducibility. Moreover, PEG fractionation was better for determining low Mr basic proteins.

Proteomic Analysis of Isogenic Rice Reveals Proteins Correlated with Aroma Compound Biosynthesis at Different Developmental Stages

Fragrant rice has a potent flavor compound, 2-acetyl-1-pyrroline (2AP). A better understanding of the 2AP biosynthetic pathway is gained by proteomic analysis of two isogenic lines of Thai jasmine rice, Oryza sativa L. cv. Khao Dawk Mali 105, which differ only in the aromatic gene Os2AP. The protein profiles of two lines, from six growth stages, seedling to grain filling, had 41 identifiable protein spots. Four of these spots were betaine aldehyde dehydrogenase, a key enzyme responsible for 2AP production. This enzyme occurred in every growth stage of the non-aromatic rice line except smaller amount detected in the hard grain-filling stage of the aromatic line. Glyceraldehyde 3-phosphate dehydrogenase and aspartate aminotransferase, observed in the aromatic line, may involve in the metabolism of precursors for 2AP biosynthesis. In addition, glutamine synthetase and 1-cys peroxiredoxin A which function in ammonia reassimilation and hydrogen peroxide detoxification were unique in the aromatic line. However, proteins that correspond to photosynthesis and the nutrient reservoir were only detected in lower abundances. This possibly explains why the aroma rice grain weight is low. Our study proposed the possible role of these remarkable proteins which involved in 2AP biosynthesis in jasmine rice.

Role of Chitosan on Some Physical Properties and the Urea Controlled Release of the Silk Fibroin/Gelatin Hydrogel

Natural polymers are widely used as biodegradable matrices for the controlled release technology because they can improve the performance of the materials and make them environmentally friendly. In this work, the silk fibroin (SF)/gelatin hydrogel with chitosan (CS) was prepared by solvent casting aiming to reduce the rate of urea release from the hydrogels. Results from the Fourier transform infrared confirmed that no intermolecular interactions had taken place after the addition of CS into the SF/gelatin. Furthermore, the increase of CS content in the SF/gelatin blended hydrogels caused the decrease in their porosity that affected the increase in their crystallinity, degree of swelling, water solubility, and surface hydrophobicity. The rate of urea release from the hydrogels also depended on the content of CS of which its value of diffusion exponent characteristics (n) determined from the Korsmeyer-Peppas model for SF/gelatin/CS hydrogels were greater than 1.0. This indicated that the urea release from the SF/gelatin hydrogels with CS was a super case II transport type. Moreover, the urea release rate (k) of the SF/gelatin/CS hydrogels was lower than that of the SF/gelatin hydrogel itself indicating an extension of the urea release from the SF/gelatin hydrogels by CS which could be utilized for controlled release applications.

Effect of Gelatin on Secondary Structure, Crystallinity and Swelling Behavior of Silk Fibroin - Gelatin Hydrogels and its Application in Controlled Release of Nitrogen

Utilization of natural polymer as biodegradable matrix for the controlled releasing fertilizer can improve the performance of the materials and make them environmentally friendly. In this work, the effect of gelatin on the properties of hydrogels was investigated. The silk fibroin (SF)-gelatin hydrogels were prepared by solvent casting and β-crystallization of SF was promoted via methanol treatment. The secondary structure and the crystallinity of the blended hydrogels were investigated using Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction analysis (XRD), respectively. Moreover, the swelling ratio of the hydrogels and also their kinetics of nitrogen (N) release were also studied. Results from the FT-IR confirmed that no intermolecular interactions had taken place between SF and gelatin. Furthermore, the increase of gelatin content in the blended hydrogels caused the decrease of the SF crystallinity detected by XRD which corresponded to the swelling behavior of the hydrogel. The release rate of nitrogen (N) depends on the composition of SF and gelatin of which its value of diffusion exponent characteristics (n) determined from the Korsmeyer-Peppas model for all of the hydrogels are smaller than 0.5. This indicates that the release of N from the hydrogels is a quasi-Fickian diffusion. Moreover, the release rate (k) and diffusion coefficient (D) of the SF-gelatin hydrogels are lower than those of the SF itself indicating a potential to use the SF-gelatin hydrogel for nitrogen controlled release application.

Application of the PEGDE Modified Silk Fibroin Membrane to an Amperometric Glucose Biosensor

Stable silk fibroin (SF) membranes were prepared by modifying SF with polyethylene glycol diglycidyl ether (PEGDE) for use as enzyme immobilizing matrix. Morphology, structure, and water solubility of the modified silk fibroin (MSF) membrane were investigated. SEM images revealed greater porosity in the MSF membranes. IR spectra confirmed the predominant β-sheet conformation when the PEGDE was greater than 4%. In addition, the MSF membranes were highly insoluble within the pH range 4 10. An amperometric glucose biosensor was initially constructed using glucose oxidase (GOx) immobilized on the MSF membrane, coupled to a Prussian Blue (PB) deposited Au electrode. The response characteristics of the biosensors based on the GOx immobilized onto the 4% and 8% PEGDE modified SF membranes (4P-MSF and 8P-MSF) and the methanol treated SF membrane (MT-SF) were investigated. Amperometric measurements at the applied potential of 0.0 V demonstrated that the glucose biosensor based on the GOx immobilized onto the 4P-MSF membrane exhibited high sensitivity to glucose with a short response time, less than 3 s. Moreover, the stability of the biosensors based on the 4P-MSF membranes was better than those based on the MT-SF membrane after 2 weeks of storage in a phosphate buffer of pH 7.0 at 4 °C. These fundamental electroanalytical features of the sensor are therefore expected to be useful in biosensor application