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排序方式: 共有1216条查询结果,搜索用时 671 毫秒
71.
Jorunn Skjermo Trond R. Størseth Karina Hansen Gunvor Øie 《Aquaculture (Amsterdam, Netherlands)》2006,261(3):1088-1101
Stimulation of the non-specific defence enhances the disease resistance and growth, and has good potentials as a measure for increased microbial control in juvenile production of marine fish and shellfish. So far, the most commonly used immunostimulants are β-(1 → 3, 1 → 6)-glucans, and in this study the stimulatory potential of a β-(1 → 3, 1 → 6)-glucan of marine origin, the storage polysaccharide from the marine diatom Chaetoceros mülleri, was examined. The glucan (chrysolaminaran) was extracted from cultures of C. mülleri, and used as a dietary supplement in two first feeding experiments with larvae of Atlantic cod Gadus morhua L. In one experiment the microalgal glucan was compared to the commercial yeast-glucan product MacroGard®, and in the other to an alginate with a high content of mannuronic acid (High-M alginate) isolated from Durvillaea antarctica. The stimulants were given via rotifers, and weaning to formulated feed was initiated at day 17 or 18 after hatching. The survival ± SEM at day 27 after hatching was 24.5 ± 2.0%, 14.8 ± 4.5% and 13.1 ± 1.4% for the groups fed C. mülleri-glucan, yeast glucan and for the control, respectively, in the first experiment. The group fed C. mülleri-glucan group had higher survival compared to the control (P < 0.05) group, whereas the yeast glucan had no positive effect on the survival (p > 0.05). The dry weights of the groups at day 27 were low, with 203.2 ± 52.2, 165.2 ± 43.4 and 198.5 ± 58.1 μg per larva for the C. mülleri-glucan, yeast glucan and control groups, respectively. In the second experiment the survival in the period of feeding formulated feed (days 18-30) were 44.6 ± 4.3%, 44.7 ± 1.3%, and 33.8 ± 4.1% survival for the C. mülleri-glucan, High-M alginate and control group, respectively. The cod larvae fed C. mülleri-glucan reached an average weight of 531.6 ± 17.2 μg at day 30, which was significantly higher (p < 0.05) than the control group that had an average of 473.6 ± 3.5 μg. The larvae fed High-M alginate had an average weight of 470.3 ± 31.6 μg per larva at day 30, and not significantly different from the control (p > 0.05). The early weaning to formulated diet had detrimental effect on the growth of the larvae. In both experiments the C. mülleri-glucan group was the only group showing a positive growth rate in the period of weaning to dry feed. The microbial conditions in larval gut and water were monitored with respect to total colony forming units on Marine agar, and Vibrio- and Pseudomonas-like species on selective agars (TCBS and marine Pseudomonas Agar with CFC-supplement). The larvae were rapidly colonised after hatching, but no or weak effects of the stimulants were observed on the colonisation rates or the composition. The total CFU varied from 101 to 102 CFU per μg larva after initiation of the first feeding. The percentages of Pseudomonas-like bacteria increased throughout the period, whereas the levels of Vibrio-like bacteria were low and stable. The chrysolaminaran from the diatom C. mülleri was shown to be a promising candidate for use as an immunostimulatory feed additive, and which should be further explored. 相似文献
72.
《The Journal of Applied Poultry Research》2014,23(4):715-723
The experimental design consisted of 5 dietary treatments including a positive control (PC), a negative control (NC; with a reduction of 88 kcal/kg of AME through the starter and grower 1 phase and a reduction of 132 kcal/kg of AME in the grower 2, finisher, and withdrawal phases compared with the PC), and the NC supplemented with either β-mannanase, nonstarch polysaccharide-degrading enzymes (NSPase; cocktail carbohydrase), or β-mannanase and NSPase intermittently fed. The intermittent treatment included β-mannanase from d 1 to 21 (starter and grower 1 phases) and NSPase from d 22 to 47. Each treatment included 9 replicate pens with 35 male broilers placed per replicate (1,575 total chicks placed). The dietary program consisted of 5 dietary phases, including the starter through d 10, grower 1 through d 21, grower 2 through d 32, finisher through d 40, and withdrawal through d 47. Broilers were weighed and feed consumption determined on days of dietary changes. On d 48, following an 8-h feed withdrawal, 6 broilers from each replicate pen were removed and processed for whole bird and fat pad measurements. The reduction in energy in the NC diet reduced BW and increased mortality rate, and the inclusion of β-mannanase and NSPase separately and intermittently in the NC diet improved growth performance and reduced mortality to levels that were comparable to the PC. The NC yielded the highest cumulative mortality-corrected FCR and all enzyme inclusion treatments reduced FCR to levels comparable to the PC for the duration of the trial. The NC diet yielded the lowest processing yields and the inclusion of β-mannanase and NSPase separately and intermittently increased multiple processing parameters to a level similar to the PC. These data confirm the ability of β-mannanase and NSPase inclusion separately and intermittently to improve performance parameters in reduced-energy broiler diets. 相似文献
73.
Indaziflam is a preemergent herbicide widely used for the control of weeds in pecan (Carya illinoinensis) orchards in the southwestern region of the United States. Given the paucity of data regarding the effect of indaziflam on the biochemical properties of soils supporting pecan production, this study was conducted to evaluate the effects of different application rates of indaziflam on soil microbial activity, diversity, and biochemical processes related to nitrogen (N) cycling. During two consecutive growing seasons (2015 and 2016), soil samples were obtained from experimental mesocosms consisting of soil-filled pots where pecan saplings were grown and treated with indaziflam applied at two different rates (25 and 50 g active ingredient (ai) ha-1, with the higher rate being slightly lower than the recommended field application rate of 73.1 g ai ha-1). Soil samples were collected approximately one week before and one week after herbicide application for determination of soil microbial biomass and diversity, N mineralization, and β-glucosaminidase activity. Soil samples collected from the control mesocosms without herbicide application were treated in the laboratory with two rates of indaziflam (75 and 150 g ai ha-1) to determine the immediate effect on microbial activity. No significant effect of herbicide treatment on soil respiration and microbial biomass was detected. The results showed a slight to moderate decrease in microbial diversity (7% in 2015 and 44% in 2016). However, decreased β-glucosaminidase activity with herbicide treatment was observed in soils from the mesocosms (33%) and soils treated with indaziflam in the laboratory (45%). The mineral N pool was generally dominated by ammonium after indaziflam application, which was consistent with the drastic decrease (75%) in nitrification activity measured in the laboratory experiment. The results of this study indicate that indaziflam, even when applied at higher than recommended rates, has limited effects on soil microbial activity, but may affect N cycling processes. 相似文献
74.
天然β-胡萝卜素提取工艺研究进展 总被引:2,自引:0,他引:2
β-胡萝卜素是维生素A的重要来源并且可作为食品着色剂,同时其突出的抗癌特性和抗氧化性使其成为日常膳食补充剂的理想选择。综述了国内外近十年来不同来源的生物原料中天然β-胡萝卜素提取工艺的研究概况,将其归纳为有机溶剂萃取法、超临界CO2萃取法、超声波辅助萃取法、微波辅助萃取法和酶解辅助萃取法,并对比了各种方法的优缺点,以期为今后β-胡萝卜素及其他天然色素特别是类胡萝卜色素的提取与开发提供参考。 相似文献
75.
76.
77.
[目的]确定从三孢布拉氏霉干菌体中提取β-胡萝卜素的溶剂种类及提取条件。[方法]以发酵所得的三孢布拉氏霉干菌丝体为原料,通过单因素试验考察了不同溶剂种类、料液比、提取时间和提取温度对β-胡萝卜素提取得率的影响。[结果]试验得出,乙醇提取得率较低,而丙酮、石油醚、乙酸乙酯和正己烷4种溶剂从三孢布拉氏霉干菌体中提取β-胡萝卜素的得率几乎相同。从价格因素考虑,选取石油醚作为提取溶剂。适宜的提取条件为料液比1∶15 g/ml,提取时间2 h,提取温度40℃,提取得率可达约16 mgβ-胡萝卜素/g干菌体。[结论]该研究可为利用三孢布拉氏霉发酵法生产天然β-胡萝卜素提供依据和参考。 相似文献
78.
[目的]对重组毕赤酵母菌表达β-甘露聚糖酶的诱导条件进行优化。[方法]以重组毕赤酵母GS115为研究对象,通过单因素试验确定最佳产酶条件,并采用响应面试验确定3个因素的最佳水平。[结果]最佳产酶条件为:培养温度28℃,培养pH 6.5,摇床转速210 r/min,培养基装液量100 ml。响应面试验确定3个因素即装液量、甲醇添加量和pH最佳值分别为103.18 ml、1.77%和6.69;在此条件下,β-甘露聚糖酶的活力最大值为4 917.5 U/ml。[结论]验证试验证明模型预测值准确、可靠,为重组毕赤酵母菌的合理开发利用提供了依据。 相似文献
79.
对石菖蒲、当归挥发油的提取及β-环糊精包合工艺进行了研究。以挥发油提取率及包合率为评价指标,采用正交试验法优选最佳提取及包合工艺条件,并采用薄层色谱法(TLC)、紫外光谱分析法(UC)及红外光谱分析法(IR)对包合物进行分析鉴定。得到最佳提取工艺:药材粉碎度粗粉10目,无需浸泡,提取时间8h;最佳包合工艺条件:mL(挥发油)与g(β-环糊精)的投料比=1∶8,包合温度60℃,搅拌时间2h,所形成的包合物通过TLC、UC、IR法证实工艺稳定、可行,为其在生产中的应用提供了依据。 相似文献
80.