Abstract: Four samples of Nham Hed which fermented from different carbon sources; Homnil rice (HN), sticky rice (SR), LeumPua rice (LP) and rice berry (RB) were evaluated for total viable count of lactic acid bacteria (LAB). The rice berry Nham Hed samples showed the highest of total lactic bacteria count with values 2.83 x 105 cfu/g. The thirty one distinct colonies of LAB were isolated and categorized into 6 groups on the basis of their colony characteristics on MRS agar, microscopic morphology and biochemical characteristic. These 6 isolates were screened for their antimicrobial activity against 2 strains of coliform bacteria and it was found that LAB isolate E exhibited the highest antimicrobial activity against Escherichia coli and Enterobacter sp. which the zone of inhibition zone 14.22 ± 1.50 mm and 13.38 ± 1.25 mm, respectively. According to the morphology characterization, isolate E was probably classified to Weissella spp. These obtained results revealed the possibility for further characterization and purification the antimicrobial compound produced by the studied isolate as food bio preservatives to control food spoilage and pathogenic bacteria.
Abstract: Turmeric (Curcuma longa L.), a member of Zingiberacaeae, is used for Thai traditional medicine, flavoring, preservative, and coloring agent. In Southern Thailand, turmeric is a famous ingredient for food recipes. Not only is the ripened rhizome used for cuisine, but also the young rhizomes. Previous studies have indicated that a variety of turmeric products from the ripened rhizome are valuable source of antioxidant compounds. However, there are ambiguous data regarding the level of antioxidant activity of the young rhizome. The aim of this study was to investigate the level of total phenolic content (TPC) and antioxidant activity of the young rhizomes by comparing to the ripened rhizome. TPC and antioxidant activity of aqueous and 80% methanolic extracts from the young turmeric grown in Southern Thailand were estimated using the Folin-Ciocalteu method and DPPH free radical scavenging activity (DPPH-RSA) assay, respectively. Results showed that the concentration of TPC determined in methanolic extract (19.80±0.25 mg GAE/ g extract) from the young rhizome was significantly higher than the corresponding aqueous extract (18.38±0.41 mg GAE/ g extract). The aqueous and methanolic extracts exhibited significant inhibition in DPPH-RSA with the half-maximal inhibitory concentration (IC50) value of 5.88±0.70 mg/mL and 3.00±0.31 mg/mL, respectively. However, in comparison with the ripened rhizome, TPC and DPPH-RSA of the young rhizome were lower. These results indicate that the young rhizome grown in Southern Thailand could be a source of antioxidant compounds, but the ripened rhizome provides better antioxidant properties than the young rhizome.
Abstract: Sizes of silver nanoparticles (AgNPs) have been shown to affect the biological activity of AgNPs. Hydrogel beads loaded with AgNPs have been extensively employed for biomedical applications. However, the influence of AgNPs sizes on biological activity of AgNP-loaded hydrogel beads has not much studied. Our objectives were to investigate the effect of AgNP sizes on the antibacterial activity, the cyto- and genotoxicity of AgNPs/alginate hydrogel beads. AgNPs of different sizes (⁓10 nm for S-AgNPs, and ⁓50 nm for L-AgNPs) were incorporated into alginate hydrogel beads during the preparation. The results showed that, S-AgNPs/alginate hydrogel beads (⁓89% inhibition) at AgNP concentration of 10 µg/ml tended to inhibit the growth of E. coli greater than L-AgNPs/alginate hydrogel beads (⁓49% inhibition) at the same dose. Moreover, at this effective antibacterial concentration (10 µg/ml), S-AgNPs/alginate hydrogel beads exhibited weak cytotoxic effect to HaCaT cells whereas L-AgNPs/alginate hydrogel beads showed non-cytotoxicity to this cell line. Furthermore, treatment of HaCaT cells with 10 µg/ml of S-AgNPs/ or L-AgNPs/alginate hydrogel beads did not result in a significant change in %DNA in tail when compared to untreated cells. Therefore, these AgNPs/alginate hydrogel beads, especially with smaller sized AgNPs, can be used as an antibacterial biomaterial with low cytotoxicity and genotoxicity to human cells.
Abstract: A simple, rapid, selective and sensitive square wave cathodic stripping voltammetry (SWCSV) at a hanging mercury drop electrode (HMDE) for the determination of As(III), As(V) and inorganic As(total) in seaweed was developed. The method was based on the formation of copper-arsenic intermetallic compound in the presence of HCl onto a HMDE at a constant potential of -0.40 V vs. Ag/AgCl in the deposition step, followed by the reduction of deposited compound to arsine at a potential of -0.78 V in the stripping step. In the system, only As(III) was directly measured, whereas inorganic As(total) was measured by reducing As(V) to As(III) using thiosulfate. In the deposition step, the use of 10 mg L-1 Cu(II) and 1 M HCl was recommended for the determination of 2 µg L-1 As(III) under the optimum instrumental variables obtained at 150 s for deposition time and 2000 rpm for stirring speed with the highest deposition efficiency of 16.15 and 88.49%, respectively. In the determination of As(V), two values of the highest reduction efficiency obtained using concentration of 40 mg L-1 thiosulfate, and reducing time at 300 s were 98.15% and 37.89%, respectively. In the measurement, the quantification limits of As(III) and As(V) were 0.46, and 1.62 µg L-1, respectively. The relative standard deviation (n=10) for 2 ug L-1 As(III) and As(V) were 5.20% and 2.57%, respectively. The proposed method was applied to the determination of inorganic arsenic species in seaweed Gracilaria fisheri.
Abstract: Antioxidant plays an important role in inhibiting and scavenging radicals, thus providing protection for human against infection and degenerative diseases. The aim of this study was to evaluate the effect of the solvent on the extraction of the antioxidant compounds from Careya arborea (CA) Roxb. The leaves of CA were extracted by using water, ethanol, methanol, and chloroform. The total phenolic content of the extracts was determined by the Folin-Ciocalteu reagent and their antioxidant activity was measured using 2, 2-diphenyl-1 picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) methods. The antioxidant activities of the extracts for DPPH and FRAP were in the order: water > methanol > ethanol > chloroform extract. According to the results, water is the most suitable solvent for extraction of active substances with antioxidant activities.
Abstract: The effects of reduced water activity and different packaging materials were investigated regarding shelf life extension of Thai red curry paste and sour curry paste. Curry pastes supplemented with 10% sodium chloride and dried at 50°C for 120 minutes and original red and sour curry pastes were evaluated for physical, chemical and microbiological properties. Results showed that L*, a*, and b* values and total viable count in supplemented curry pastes were less than in original curry pastes. Staphylococcus aureus, Bacillus cereus, Clostridium perfringens, Salmonella spp. and Escherchia coli were not detected in both supplemented and original curry pastes. Protein, fat, fibre, carbohydrate, total phenolic content and IC50 value of supplemented curry pastes did not differ from the original curry pastes. Both supplemented and original curry pastes were vacuum packed in aluminium foil and nylon bags and stored at 25°C for 8 weeks. Results revealed that nylon bags gave higher shelf life extension for supplemented curry pastes over the storage period. Values of water activity, moisture, aflatoxin, total viable count and mould count in supplemented curry pastes packed in nylon bags were less than the Thai community product standards.
Abstract: An effective biosurfactant-producing bacteria, isolate L5, was isolated from mangrove sediments from both east coast and west coast of Southern of Thailand. Analysis of the 16S rRNA gene sequence confirmed that isolate L5 was Agrobacterium rubi with 100% homology. The biosurfactant production was performed using a mineral salt medium (MSM) with molasses as a carbon and commercial monosodium glutamate (MSG) as nitrogen sources. Under optimized conditions, A. rubi L5 was able to grow and produce biosurfactant with the yield of 4.62 g/l at 54 h of cultivation. It could reduce the surface tension of pure water from 72.0 to 25.5 mN/m and exhibit emulsification activity toward palm oil with 65.4%. The biosurfactant found to be stable even under extreme pH, temperature and salinity conditions. The results revealed the potential use of a biosurfactant produced by A. rubi L5 to enhance mobilization sorbed motor oil from environment in comparison with those of synthetic surfactants, i.e. a nonionic surfactant Tween 80 and anionic surfactants sodium dodecyl sulfate.
Abstract: In this work, Au-TiO2 nanoparticles (NPs) were synthesized in a single step by flame spray pyrolysis (FSP) method. X-ray diffraction (XRD) results indicated that phase structures of all samples TiO2 were the mixture of anatase and rutile phases. High resolution transmission electron microscopy (HRTEM) showed that dark spots of Au NPs deposited on larger TiO2 nanoparticles. HRTEM results indicated TiO2 NPs were average crystallite size in the range of 10–30 nm whereas the average diameter of Au NPs was about 5–10 nm. UV–Vis absorption spectroscopy technique showed peaks attributable of surface plasmon resonance (SPR) to Au NPs loaded on TiO2 in the wavelength of 500–630 nm. The Au-TiO2 NPs showed excellent photocatalytic activity for the degradation of methylene blue (MB) under UV-Vis irradiation. It was found that 0.25 mol% Au-TiO2 which was a better photocatalyst than others under the same reaction conditions. The results showed that Au NPs-loading could effectively improve the photocatalytic activities of TiO2.
Abstract: In this paper, α–Fe2O3 photocatalyst with enhanced solar–driven photocatalytic activity was obtained from natural local groundwater sediment using a chemical solution method with subsequent calcination. The phase structures and crystallite size characterized by X–ray diffraction. The morphology and the particle size were investigated by scanning electron microscopy. The α–Fe2O3 was used as a catalyst to photodegrade MB under visible light illumination. The photocatalytic reaction rate constant of the α–Fe2O3 photocatalyst in the photocatalytic degradation of MB dye solution under LED light illumination with the presence of H2O2 was calculated to be 1.70×10–2 min–1. Moreover, the effect of H2O2 concentration on photocatalytic efficiency and the photocatalytic mechanism also were discussed.
Abstract: In this paper, the groundwater sediment/titanium dioxide (Gs/TiO2) were prepared via a conventional calcination process using groundwater sediment from natural resource at Pasao, Uttaradit province, Thailand and commercial TiO2 as starting materials. The as–prepared were characterized by X–ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR). The photocatalytic activity toward the decomposition of agricultural residues (diazinon) at 247 nm was demonstrated under visible light irradiation for 120 min. The maximum experimental decomposition efficiency was 73.6% with the rate constant of 0.0102 min–1 for prepared Gs/TiO2 photocatalyst.