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1.
The effect of carbon/nitrogen (C/N) ratio manipulation in feed supplements on Artemia production and water quality was investigated in solar salt ponds in the Mekong Delta, Vietnam. It was assumed that development of bacterial bioflocs through C/N manipulation would improve Artemia production and water quality as demonstrated in freshwater and marine aquaculture. Twelve ponds were used for three treatments and the control, in triplicates. Green water (GW) was supplied to all ponds, with the standard Vietnamese procedure of supplying GW and chicken manure (CM) as the control (C/N 1.8). Treatment ponds were supplemented with tapioca (TAP) as carbon source, combined with either CM, pig manure (PM) or rice bran (RB), with C/N ratios of 7.4, 10.5 or 20.1 respectively. After 6 weeks of culture, no single treatment supported both improved water quality and enhanced Artemia production. Overall, improved water quality was observed at C/N 20.1 and higher Artemia production at C/N 7.4. Although external field factors could have interfered with the set‐up, this is the first study on the effect of C/N manipulation in feed supplements in Artemia pond production systems and provides the basis for development of bacterial bioflocs as a technology to improve water quality and Artemia production.  相似文献   
2.
Stable isotope analysis was used to determine the sources of dietary nitrogen (N) and carbon (C) for shrimp during the rearing phase in extensive rice‐shrimp ponds in My Xuyen and Gia Rai districts, Vietnam. Farm‐made feed was added as a food source in shrimp ponds in My Xuyen district, and based on stable isotope analyses, was generally a poor dietary source. The commercial formulated feed used in Gia Rai also appeared to contribute little directly to the nutritional needs of the shrimp. In contrast, the natural biota in all ponds appeared to contribute substantially. In particular, biota from beam trawls and benthic organic matter were the most likely sources of nutrition in My Xuyen ponds, while benthic organic matter was the main source in Gia Rai ponds. δ15N ratios in the natural biota in My Xuyen farms decreased over the growing season, suggesting increased N fixation in the case of the benthic organic matter reaching values as low as 1‰. This suggests N‐limitation in the ponds and that natural biota become increasingly dependent on N fixed by algae and/or other microorganisms. There is the potential to promote the growth of the plankton and hence, the other natural biota, by the judicious addition of fertilizer.  相似文献   
3.
The present study demonstrates the effects of different muscle types and chiller ageing periods on the chemical composition, meat quality parameters, sensory characteristics and volatile compounds of Karean native cattle beed. Longissimus dorsi (LD) and Semitendinosus (ST) muscles aged for 7 days and 28 days were used. Moisture, cooking loss, total collagen and Warner‐Bratzler shear force (WBSF) values for the ST were higher than the LD muscle regardless of ageing period (P < 0.05). The LD muscle had higher intramuscular fat (IMF) (P < 0.05). Ageing for 28 days decreased WBSF values whereas it increased thiobarbituric acid of both muscles. Moreover, tenderness, juiciness and flavor scores were significantly higher for the LD muscle at both ageing periods. Increased ageing time improved tenderness of both muscles, and increased juiciness of the LD muscle, whereas there was decreased flavor score of ST muscle (P < 0.05). The majority of the volatile compounds formed from the oxidation of lipids showed differences between the two muscles. Ageing for 28 days increased in the amounts of many volatile compounds; however, the amounts of some important volatile compounds were decreased. These results clearly demonstrate that muscle type and ageing have a potential effect on meat quality, sensory characteristics and volatile profile.  相似文献   
4.
5.
A commercial high-methoxy citrus pectin was treated with a purified salt-independent pectin methylesterase (PME) isozyme isolated from Valencia orange peel to prepare a series of deesterified pectins. A series of alkali-deesterified pectins was also prepared at pH 10 under conditions permitting beta-elimination. Analysis of these pectins using high-performance size exclusion chromatography (HPSEC) with on-line multiangle laser light-scattering, differential viscometer, and refractive index (RI) detectors revealed no reduction in weight-average molecular weight (M(w); 150000) in the PME-treated pectin series, whereas a 16% reduction in intrinsic viscosity (IV) occurred below a degree of esterification (DE) of 47%. In contrast, alkali deesterification rapidly reduced both M(w) and IV to less than half of that observed for untreated pectin. PME treatment of a non-calcium-sensitive citrus pectin introduced calcium sensitivity with only a 6% reduction in the DE. Triad blocks of unesterified galacturonic acid were observed in (1)H nuclear magnetic resonance spectra of this calcium-sensitive pectin (CSP). These results demonstrate that the orange salt-independent PME isozyme utilizes a blockwise mode of action. This is the first report of the preparation of a CSP by PME treatment without significant loss of the pectin's M(w) due to depolymerization.  相似文献   
6.
ABSTRACT

In

-situ sorbent amendment is a relatively low-cost, low-impact approach for remediation of soil contaminated with heavy metals (HMs), and thus is considered a way to be favored in developing countries. In this study, materials of non-hazardous, alkaline agronomic and industrial by-products were used as sorbents to explore their capacity of in situ immobilization of multiple HMs in mining-impacted arable soil. These sorbents included fly ash (FA), biochar (BC) and apatite (AP) and they were implemented with varying ratios of combinations. Results of soil microcosm tests showed that after incubation for 90 days, concentrations of Pb, Zn, and Cd in their exchangeable forms determined by a sequential extraction method significantly decreased in amended soils, as opposed to the unamended control. Of the five sets of amendments, the composite of FA, BC, and AP resulted in the maximum reduction (up to 80%) in the mobility of Pb, Zn, and Cd in soils. The mechanisms underlying the immobilization of HMs in amended soils might involve processes of surface precipitation, ion exchange and complexation, in which the physicochemical properties of sorbent materials played an important role. The immobilization efficacy of sorbent amendments on HMs in soil was further supported by pot experiments in which significant inhibition of HM accumulation in the belowground and aboveground tissues of maize was observed after 50-day cultivation in amended soils as compared with control soil. Together, these results suggest that the application of cost-saving and environmentally friendly materials derived from wastes as sorbents to remediate soils contaminated with multiple HMs is promising for developing countries like Vietnam.  相似文献   
7.
Global structure of microwave-assisted flash-extracted sugar beet pectin   总被引:3,自引:0,他引:3  
The global structure of microwave-assisted flash-extracted pectins isolated from fresh sugar beet pulp has been studied. The objective was to minimize the disassembly and possibly the degradation of pectin molecules during extraction. These pectins have been characterized by high-performance size exclusion chromatography with light scattering, viscometric detection, and atomic force microscopy (AFM). Analysis of molecular parameters was performed on 15 and 8 microm size column packings. Samples analyzed with 15 microm packing gave weight-average molar masses that ranged from 532,000 to 1.2 million Da, radii of gyration from about 35 to 51 nm, polydispersities from 1.78 to 2.58, intrinsic viscosities from about 3.00 to 4.30 dL/g, and recoveries from 8.40 to 14.81% of dry weight. Chromatography revealed that a bimodal distribution of high molar mass spherical particles and lower molar mass coils was obtained. AFM images of pectin corroborated this conclusion and further revealed that these strands and spherical particles were integrated into networks. It is demonstrated that microwave-assisted extraction of sugar beet pulp under moderate pressure and at relatively low temperature could extract under acid conditions high molar mass, moderate-viscosity pectin in minutes rather than hours as required by conventional heating.  相似文献   
8.
Unidirectional mass truncation selection for small‐sized cysts was carried out on brine shrimp (Artemia franciscana Kellogg 1906), Vinh Chau strain, Vietnam, through cyst sieving and then culturing the selected individuals (<5% of the population) under field and laboratory conditions over two successive generations (F1 and F2). The results showed that at both culture scales, the cyst size of the selected line was smaller (P < 0.05) compared with the control (non‐selected) line, illustrating that there was a response to selection. The cyst size decreased about 3% per generation and the accumulated gain on the target trait was in the range 5.82–6.07% at the end of the selection process compared with the base population. The realized heritability estimation (h2) for cyst size was 0.23 ± 0.06 and 0.74 ± 0.19 in the field trials and 0.34 and 0.51 in the laboratory test for the F1 and F2 generation respectively. The variations found between the respective trials may be explained as the result of environmental interaction with the selection process, but the results show that a selection program for small‐sized cysts in Artemia by mass selection is possible.  相似文献   
9.
Rat bite fever     
Rat bite fever (RBF) is a bacterial zoonosis for which two causal bacterial species have been identified: Streptobacillis moniliformis and Spirillum minus. Haverhill fever (HF) is a form of S. moniliformis infection believed to develop after ingestion of contaminated food or water.  相似文献   
10.
越南不同龙眼品种品质分析比较(英文)   总被引:1,自引:0,他引:1  
[目的]筛选出适合越南当地生产的龙眼品种。[方法]分别对引种至越南农科院北部山区农林研究所内栽培的5个龙眼品种的果实植物学性状和品种果实性状进行了比较分析。[结果]筛选出了可作为鲜食的优良龙眼品种PMP6,PHS1-1以及可用于加工的优良品种HuongChi。[结论]本研究将对越南北部山区的龙眼生产、育种提供参考。  相似文献   
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