Potassium contents of northeastern Thai foods

From our previous nutritional assessment, low potassium (K) intake among northeastern Thai males has been clearly demonstrated. This prompted us to undertake a survey of the K content of local foods. Food samples comprised of 57 animal and 142 plant products which were collected from various places in the northeast of Thailand. The dry ashing method was used to prepare the samples for K analysis using an atomic absorption spectrophotometer. Foods could be divided into 7 groups according to their K levels. Foods containing K > or = 1000 mg per 100 g fresh food were categorized in group 1. These were mainly foods in the legume group, i.e., soybean, cowpea and mungbean. While rice (polished) and rice products, the main staple, were in group 7, the lowest K group of less than 100 mg per 100 g fresh food. Comparison studies of the natural foods between those collected from the northeast and from the central regions of the country, and between the cooked foods purchased from the rural villages and from the urban areas of Khon Kaen municipality, showed that, for most food items, the K content was similar wherever it came from. However, when the K content in various parts or in different stages of growth of the same kind of plants or animals was compared, a great variation was clearly seen, for example, young tamarind leaves contained K in group 6 whereas ripe tamarind fruit contained K in group 1. According to our food consumption data, the analysis of food components of 48 meals taken during the hot season by 13 rural volunteers revealed that food items eaten with the highest frequencies and in the largest amount were those in the low K food groups, i.e., glutinous rice (group 7) and green papaya (group 6). Our results suggest that the low K intake of these northeast rural Thai people is not due to a low K content of foods in this region, but rather that their food habits and low socioeconomic status restricts consumption of those food items with higher K contents.     

Reconstitution and function of Tetragenococcus halophila chaperonin 60 tetradecamer

Tetragenococcus halophila originally isolated from soy sauce is a halophilic lactic acid bacterium which can grow under 4 M sodium chloride. T. halophila chaperonin composed of a core moiety of chaperonin 60 (cpn60) and a lid moiety of chaperonin 10 (cpn10), is thought to contribute to host halotolerant capability. In this report, we reconstituted and characterized the core complex of T. halophila chaperonin by using a recombinant T. halophila cpn60 (Tcpn60) overexpressed in Escherichia coli. The reconstitution of Tcpn60 was performed in the presence of 10 mM MgCl2, 2 mM ATP and 0.8 M (NH4)2SO4 and the resultant oligomer was purified by gel filtration chromatography. Electron microscopy of the reconstituted Tcpn60 revealed a double toroidal tetradecameric structure that is characteristic of bacterial cpn60. The T. halophila tetradecamer cpn60 exhibited an ATPase activity and a refolding activity of both chemically and thermally denatured enolases under wide range of salt concentrations. Furthermore, we demonstrated that heterologous expression of Tcpn60 allowed the normal growth of host Escherichia coli cells under salt stress conditions and this effect was further enhanced by co-expression with Tcpn10. These results suggested that Tcpn60 contributes to the halotolerance property of T. halophila cell as a tetradecamer complex, probably associated with the Tcpn10 complex.     

Anti-listeria activity of Pediococcus pentosaceus BCC 3772 and application as starter culture for Nham, a traditional fermented pork sausage

Lactic acid bacteria forming bacteriocin active against Listeria monocytogenes were screened for potential use in controlling growth of L. monocytogenes in Nham, a Thai traditional fermented pork sausage. Based on the spot-on-lawn assay, Pediococcus pentosaceus BCC 3772 was found to produce the highest anti-listeria activity. Through a series of chromatographic techniques, Edman N-terminal sequencing and mass spectrometry, this anti-listeria compound showed a complete homology to pediocin PA-1/AcH. Inoculation of P. pentosaceus BCC 3772 in Nham caused a significant decrease of 3.2 log in population of spiked L. monocytogenes within 18-24 h of fermentation, in comparison with the initial count with no significant changes in sensory properties and consumer acceptability on the overall characteristics of the final fermented Nham products. These results indicate that the P. pentosaceus BCC 3772 should be useful as a functional starter culture for control of L. monocytogenes without compromising the unique quality of Nham.     

Biogenic amine formation in Nham,a Thai fermented sausage,and the reduction by commercial starter culture, Lactobacillus plantarum BCC 9546

Biogenic amines are of concern for sausage due to their toxicological effects on nervous, blood pressure, gastric and intestinal systems. In this study, the influence of raw pork meat quality and starter culture inoculation on biogenic amines accumulation in Nham, a Thai traditional fermented pork, were studied. Before Nham processing, pork meat was stored at 30 °C for 6 h, and at 4 and −20 °C for 2 days. Formation of biogenic amines (cadaverine, putrescine, histamine and tyramine) was significantly higher in Nham processed from stored meat. Accumulation of these biogenic amines in Nham reduced significantly by the addition of Lactobacillus plantarum BCC 9546, a commercial Nham starter culture. The results highlight the importance of using fresh meat products and the inclusion of an appropriate starter culture to minimise the formation of biogenic amines during the process of Nham fermentation.     

Hydrogenation of Succinimide to 2-Pyrrolidone Over Solid Catalysts

2-Pyrrolidone (P-Done) is an important chemical which is widely used both as a solvent and as an intermediate in industrial syntheses. The preparation of P-Done by the catalytic hydrogenation of succinimide has attracted little attention. Previous attempts to carry out this reaction resulted in low reaction rates and poor selectivity towards the desired product. Here, we present the results of the selective catalytic hydrogenation of succinimide to P-Done in the presence of skeletal nickel catalysts in aqueous and non-aqueous solvents.     

Effect of heterologous expression of molecular chaperone DnaK from Tetragenococcus halophilus on salinity adaptation of Escherichia coli

Molecular chaperone DnaK of halophilic Tetragenococcus halophilus JCM5888 was characterized under salinity conditions both in vitro and in vivo. The dnaK gene was cloned into an expression vector and transformed into Escherichia coli. The DnaK protein obtained from the recombinant E. coli showed a significantly higher refolding activity of denatured lactate dehydrogenase than that from non-halophilic Lactococcus lactis under NaCl concentrations higher than 1 M. E. coli without the overexpression of DnaK exhibited a growth profile with a prolonged lag phase and suppressed maximum cell density in Luria-Bertani medium containing 5% (0.86 M) NaCl. On the contrary, the overexpression of T. halophilus DnaK greatly shortened this prolonged lag phase with no effect on maximum growth, while that of L. lactis DnaK decreased maximum growth. The amount of protein aggregates was increased by salt stress in the E. coli cells, while this aggregation was greatly suppressed by the overexpression of T, halophilus DnaK. These results suggest that heterologous overexpression of T. halophilus DnaK, via its chaperone activity, promotes salinity adaptation of E. coli.     

Hydrogenation of Succinimide to 2-Pyrrolidone Over Solid Catalysts

2-Pyrrolidone (P-Done) is an important chemical which is widely used both as a solvent and as an intermediate in industrial syntheses. The preparation of P-Done by the catalytic hydrogenation of succinimide has attracted little attention. Previous attempts to carry out this reaction resulted in low reaction rates and poor selectivity towards the desired product. Here, we present the results of the selective catalytic hydrogenation of succinimide to P-Done in the presence of skeletal nickel catalysts in aqueous and non-aqueous solvents.