Stability and emulsion-forming ability of water-soluble fish myofibrillar protein prepared by conjugation with alginate oligosaccharide

Carp myofibrillar protein (Mf) was conjugated with alginate oligosaccharide (AO) through the Maillard reaction under low relative humidity, and the functional properties of the Mf-AO conjugate were investigated under different NaCl concentrations and pH levels. Mf became highly solubilized at lower NaCl concentrations by conjugation with AO, with a slight loss of available lysine. The thermal stability of Mf was effectively improved by conjugation with AO. Heat treatment at 80 degrees C for 2 h had no effect on the solubility of the Mf-AO conjugate attached to 227 microg/mg of AO regardless of the NaCl concentration and pH. Furthermore, the Mf-AO conjugate showed excellent emulsion-forming ability regardless of NaCl concentration. The improved functionalities of Mf by conjugation with AO remained even at a nearly isoelectric point. These results indicate that conjugation with AO through the Maillard reaction is an effective way to prepare high-functional food material from fish muscle protein.     

Methane emissions from different vegetation zones in a Qinghai-Tibetan Plateau wetland

We measured methane (CH₄) emissions in the Luanhaizi wetland, a typical alpine wetland on the Qinghai-Tibetan Plateau, China, during the plant growth season (early July to mid-September) in 2002. Our aim was to quantify the spatial and temporal variation of CH₄ flux and to elucidate key factors in this variation. Static chamber measurements of CH₄ flux were made in four vegetation zones along a gradient of water depth. There were three emergent-plant zones (Hippuris-dominated; Scirpus-dominated; and Carex-dominated) and one submerged-plant zone (Potamogeton-dominated). The smallest CH₄ flux (seasonal mean=33.1 mg CH₄ m⁻² d⁻¹) was observed in the Potamogeton-dominated zone, which occupied about 74% of the total area of the wetland. The greatest CH₄ flux (seasonal mean=214 mg CH₄ m⁻² d⁻¹) was observed in the Hippuris-dominated zone, in the second-deepest water area. CH₄ flux from three zones (excluding the Carex-dominated zone) showed a marked diurnal change and decreased dramatically under dark conditions. Light intensity had a major influence on the temporal variation in CH₄ flux, at least in three of the zones. Methane fluxes from all zones increased during the growing season with increasing aboveground biomass. CH₄ flux from the Scirpus-dominated zone was significantly lower than in the other emergent-plant zones despite the large biomass, because the root and rhizome intake ports for CH₄ transport in the dominant species were distributed in shallower and more oxidative soil than occupied in the other zones. Spatial and temporal variation in CH₄ flux from the alpine wetland was determined by the vegetation zone. Among the dominant species in each zone, there were variations in the density and biomass of shoots, gas-transport system, and root-rhizome architecture. The CH₄ flux from a typical alpine wetland on the Qinghai-Tibetan Plateau was as high as those of other boreal and alpine wetlands.     

Apricot carotenoids possess potent anti-amyloidogenic activity in vitro

Alzheimer's disease (AD) is the most common form of dementia and is characterized by the progressive accumulation of amyloid β protein (Aβ) in areas of the brain. There has been an increased interest in screening for food-grade anti-amyloidogenic compounds in foodstuffs. The purpose of this study was to screen and identify bioactive compounds with anti-amyloidogenicity in apricot fruits using synthetic Aβ(1-42). The anti-amyloidogenicity was investigated using thioflavin T fluorescence assay, electron microscopy, and dot blotting analysis. The carotenoid fraction from apricot showed strong inhibitory effects against oligomer and fibril formation of Aβ and fibril-destabilizing effects. Among the peaks in the HPLC chromatogram, lutein showed the strongest inhibitory effect on Aβ fibril formation. The inhibitory effect was dependent on the number and portion of hydroxyl groups on both sides of carotenoids. These findings suggest that lutein in fruits may be useful as a preventive agent for amyloid-associated diseases.     

Chemical characteristics and potential source of fulvic acids leached from the plow layer of paddy soil

To understand better the chemical characteristics and source of dissolved organic matter (DOM) leached from the plow layer of rice paddies, a lysimeter study was conducted, which simulated submerged paddy topsoil during rice growth. The fulvic acid (FA) fraction in the percolation water from the lysimeter was collected by adsorption onto insoluble polyvinylpyrrolidone (PVP), and the temporal variations in its elemental composition, molecular size distribution, IR spectra, ¹³C CPMAS NMR spectra, and δ¹³C values were investigated. The proportion of the FA fraction to bulk DOM varied greatly, but the chemical characteristics of the FA fraction did not change appreciably during the experimental period. Thus, it is considered that the changes in the DOM composition in percolation water were mainly due to the differing contributions of the FA fraction. Further, to investigate the source of the FA fraction in the leachate, the chemical characteristics of the FA fraction in the leachate were compared with those extracted from the plow layer soil. A sequential extraction of the FA fraction was conducted using a sequence of water, 0.25 M Na₂SO₄, 0.1 M Na₄P₂O₇ (pH 7.0), 0.1 M Na₄P₂O₇ (pH 10.5), and NaBH₄+0.1 M Na₄P₂O₇ (pH 10.5). It was found that the water- and 0.25 M Na₂SO₄-extractable fractions, which were most mobile, were not the only source of the FA fraction in the leachate. The small molecular size sub-fraction of the NaBH₄+0.1 M Na₄P₂O₇ (pH 10.5)-extractable FAs, most of which are probably bound mainly to iron oxides, are considered to be another source of the FA fraction leached from the plow layer of paddy fields.     

Influence of surface printing materials on the degradability of biodegradable plastic films in soil

Effect of surface printing on the biodegradability of plastic films was studied. Biodegradable films (polybutylene-succinate (PBS)) printed with four kinds of gravure inks were placed in soil for 1 year. The inks consisted of carbon black-pigment with four kinds of resins: poly-(ε-caprolactone) (PCL), nitrocellulose-polyamide blended resin (NT), polyvinyl chloride-vinyl acetate copolymer (V), and nitrocellulose (NC). Degradation of film specimens printed on one side and both sides as well as the control film without printing was monitored every 3 months by collecting sample specimens for the measurement of weight loss. No appreciable degradation was observed until 6 months after placement in soil for the control specimens and until 9 months for the printed specimens. And the degradation of the PCL- and NC-printed specimens with one-side printing and V-printed specimens with both-side printing was significantly slower than that of the control specimens without printing after 9-month placement at p < 0.05. Only after 12 months of placement, was the degradation significantly faster for the specimens printed on one side than for those printed on both sides except of the specimens printed with NC. There was no difference in biodegradability among PCL, NT, NC, and V resins. Specimens printed on both sides did not show any appreciable weight loss after 1 year in soil (percentage of maintenance of weight exceeding 98%). Microscopic observation indicated that the degradation mainly proceeded from the non-printed side to the printed side cross-sectionally.     

Origin and properties of humus in the subsoil of irrigated rice paddies

Stability of humus in the plow layer soil is considered to affect the quantity and quality of dissolved organic matter leached from the plow layer soil. Therefore, a model experiment was conducted to analyze the effect of soil reduction under submerged conditions on the stability of humus in the plow layer soil. The changes in the stability of humus in the plow layer soil during submerged incubations with and without rice straw application were evaluated based on the changes in the binding type of humus. Binding type of humus in the plow layer soil was analyzed by successive extractions of organic matter with water, 0.25 M Na₂SO₄, 0.1 M Na₄P₂O₇ (pH 7.0), 0.1 M Na₄P₂O₇ (pH 10.5), and 0.1 M Na₄P₂O₇ (pH 10.5) with NaBH₄. Amounts of Fe, Mn, and Mg in each fraction were also determined to estimate the relationships between humus and metals.

The successive extraction of humus indicated that the amount of organic carbon which was extractable with the (NaBH₄ +0.1 M Na₄P₂O₇) solution decreased while that of the 0.1 M Na₄P₂O₇ (pH 7.0}-extractable organic carbon increased during submerged incubation with rice straw application. The origin of the increase in the amount of organic carbon in the Na₄P₂O₇ (pH 7.0)-extractable fraction during submerged incubation was investigated further by another incubation experiment using ¹³C-glucose as a reducing agent. Atom- 13C% analysis showed that the contribution of organic carbon derived from compounds other than glucose to the increase in the contents of humic acids and fulvic acids in the Na₄P₂O₇ (pH 7.0)-extractable fractions was ca. 80%. Therefore, it was concluded that the binding type of humus changed from (NaBH₄ + Na₄P₂O₇)-extractable to Na₄P₂O₇ (pH 7.0)-extractable humus under reducing conditions. Since the amounts of organic carbon and Fe increased in the Na₄P₂O₇ (pH 7.0)-extractable fraction and decreased in the (NaBH₄ +0.1 M Na₄P₂O₇)-extractable fraction simultaneously, iron reduction was presumably associated with the change in the binding type of humus in submerged paddy soil.     

Application of N2/Ar ratio method for N2 fixation studies in submerged soil

Abstract

Recently there has been developments in the measurement of N₂ fixation due mainly to the C₂H₂ reduction method (1). This method, however, has several disadvantages, especially for submerged soil, and the estimated amount of fixed N₂ on the basis of the C₂H₂ reduction activity is not very reliable. The tracer ¹⁵N₂ technique which gives a reliable estimation of the fixed N₂ is too expensive for common use. Development of an alternative method suitable for submerged soil would therefore be desirable. The present authors expected that the measurement of the ratio N₂/Ar in the soil solution might provide advantages for the estimation of the fixed N₂ in submerged soil.     

Comparison of Bacterial Communities Associated with Microcrustaceans from the Floodwater of a Paddy Field Microcosm: Estimation Based on DGGE Pattern and Sequence Analyses

Bacterial communities associated with five kinds of microcrustaceans ( Tanycypris sp., Moina sp., Mesocyclops sp., Cypretta sp. and Heterocypris sp.) from the floodwater of a paddy field microcosm were examined by the application of denaturing gradient gel electrophoresis (DGGE) to PCR-amplified 16S rDNA products with universal bacterial primers and by sequencing of characteristic DGGE bands. The number of DGGE bands of the associated bacteria was small, indicating the association of specific bacterial members with the microcrustaceans studied, among which Tanycypris sp. showed the smallest number of bands. Principal component analysis (PCA) demonstrated that the community structure of the associated bacteria could be divided into three groups: Podocopida ( Tanycypris sp., Cypretta sp. and Heterocypris sp.), Moina sp. and Mesocyclops sp., and further analysis separated Tanycypris sp. and Heterocypris sp. into different clusters. The duration of the incubation period affected the bacteria associated with Tanycypris sp., Moina sp. and Cypretta sp. only. Nearly all of the associated bacteria belonged to Gram-negative bacteria, especially the Cytophaga-Flavobacterium-Bacteroides (CFB) group. Closest relatives of the DGGE bands common to three Podocopida and Mesocyclops sp. belonged to an invertebrate endosymbiont.     

Long-Term Observation of Fogwater Composition at two Mountainous Sites in Gunma Prefecture, Japan

We made serial observations on acid fog at Mt. Akagi and Mt. Haruna, Japan for 5 years. The altitudes of the sampling sites were 1500 m (Mt. Akagi) and 1200 m (Mt. Haruna) above sea level, and the sites were approximately 30 km apart. The average liquid water content (LWC) at Mt. Akagi and Mt. Haruna was 74 mg m^?3 and 63 mg m^?3, respectively. The pH of fogwater was 2.72–7.14 (mean 3.71) at Mt. Akagi and 2.94–6.58 (mean 3.73) at Mt. Haruna. Our long-term observations indicate that there was no significant difference in the chemical components in fogwater at both sites except for ammonium ion. However, there were some cases where the chemical components of fogwater at each site were differed remarkably even in the concurrent fog event. Nitrate and sulfate ions contributed to acidification of fogwater at Mts. Akagi and Haruna and 95% of sulfate ion in the fogwater originated from air pollution. Ammonia gas in the air was the main neutralizer of acidity in fogwater. When absorption of excessive nitric acid gas over ammonia gas in the air occurred, the pH of fogwater was lowered. Our back trajectory analysis indicated that the fogwater at Mt. Akagi was mainly affected by an air mass from the Kanto Plain, including Tokyo, while the fogwater at Mt. Haruna was influenced by an air mass from large, western cities, such as Nagoya and Osaka, as well as Tokyo.     

Diurnal variations in absorption and translocation of a ferrated phytosiderophore in barley as affected by iron deficiency

The release of phytosiderophore (PS) from roots of Fe-deficient graminaceous plants follows a distinct diurnal rhythm with maximum release rates occurring usually 3 to 4 hours after the onset of light. However, it remains to be determined whether absorption of the PS-Fe³⁺ complex shows a diurnal rhythmicity similar to that of PS release, Barley plants grown with or without 10 µM FeEDTA for 7 days were fed with ferreted PS (10 µM labelled with ⁵⁹Fe) at 4-h intervals to study the diurnal variations in the absorption and transloca tion of ⁵⁹Fe, The absorption of ⁵⁹Fe, irrespective of the Fe nutritional status of the plants, was higher during the day and lower during the night but did not show any peak throughout the day-night cycle. On the other hand, the translocation of ⁵⁹Fe into shoots of Fe-deficient plants was lower than that of Fe-sufficient plants, while the Fe nutritional status of the plants did not affect the absorption of ⁵⁹Fe by roots, The formation of root apoplastic ⁵⁹Fe was lower during the day and higher during the night, regardless of the Fe nutritional status of plants. Our results showed that the absorption of the PS-Fe³⁺ complex by roots did not follow the PS release pattern.