Effects of graded removal of lysine from an intravenously infused amino acid mixture on lactation performance and mammary amino acid metabolism in lactating goats

To investigate responses of milk protein synthesis and mammary AA metabolism to a graded decrease of postruminal Lys supply, 4 lactating goats fitted with jugular vein, mammary vein, and carotid artery catheters and transonic blood flow detectors on the external pudic artery were used in a 4 × 4 Latin square experiment. Goats were fasted for 24 h and then received a 9-h intravenous infusion of an AA mixture plus glucose. Milk yield was recorded and samples were taken in h 2 to 8 of the infusion period; a mammary biopsy was performed in the last hour. Treatments were graded decrease of lysine content in the infusate to 100 (complete), 60, 30, or 0% as in casein. Lysine-removed infusions linearly decreased milk yield, tended to decrease lactose yield, and tended to increase milk fat to protein ratio. Milk protein content and yield were linearly decreased by graded Lys deficiency. Mammary Lys uptake was concomitantly decreased, but linear regression analysis found no significant relationship between mammary Lys uptake and milk protein yield. Treatments had no effects on phosphorylation levels of the downstream proteins measured in the mammalian target or rapamycin pathway except for a tended quadratic effect on that of eukaryotic initiation factor 2, which was increased and then decreased by graded Lys deficiency. Removal of Lys from the infusate linearly increased circulating glucagon and glucose. Removal of Lys from the infusate linearly decreased arterial and venous concentrations of Lys. Treatments also had a significant quadratic effect on venous Lys, suggesting mechanisms to stabilize circulating Lys at a certain range. The 2 infusions partially removing Lys resulted in a similar 20% decrease, whereas the 0% Lys infusion resulted in an abrupt 70% decrease in mammary Lys uptake compared with that of the full-AA mixture infusion. Consistent with the abrupt decrease, mammary Lys uptake-to-output ratio decreased from 2.2 to 0.92, suggesting catabolism of Lys in the mammary gland could be completely prevented when the animal faced severe Lys deficiency. Mammary blood flow was linearly increased, consistent with the linearly increased circulating nitric oxide by graded Lys deficiency, indicating mechanisms to ensure the priority of the mammary gland in acquiring AA for milk protein synthesis. Infusions with Lys removed increased mammary clearance rate of Lys numerically by 2 to 3 fold. In conclusion, the decreased milk protein yield by graded Lys deficiency was mainly a result of the varied physiological status, as indicated by the elevated circulating glucagon and glucose, rather than a result of the decreased mammary Lys uptake or depressed signals in the mTOR pathway. Mechanisms of Lys deficiency to promote glucagon secretion and mammary blood flow and glucagon to depress milk protein synthesis need to be clarified by future studies.     

新型液压驱动式山茶籽榨油装置设计

以简化榨油机的结构,提高其工作效率、机械效率及标准化程度为目标,设计了一种新型液压驱动式山茶籽榨油机,主要由进料装置、压榨装置、多级滤油系统、液压控制系统构成,通过液压控制系统实现压榨至卸料工序的自动化操作。该液压式榨油机运用冷压榨的方式,不仅保证了山茶籽油的原香以及微量营养物质,而且出油率高,油渣分离效果好,榨出的油优质清洁。实践证明,该榨油机具有体积小、占地面积小、能耗低、压缩比大、操作简便等优点,适于在油脂企业进一步推广应用。     

Preparation and Applications of Soybean Residue CNF Films

In this study, soybean residues were treated with HCl and soybean residue cellulose was extracted, which was used to prepare cellulose nanofiber (CNF) using the high-pressure homogenization method. The maximum yield of CNF, the reaction temperature, reaction time, and HCl concentration were optimized. The optimum HCl concentration for acid treatment was 6%, the reaction time was 60 min, the reaction temperature was 80℃, and the maximum yield of soybean residue cellulose was 78.8%. The different CNF films were then prepared; the color, mechanical property, and light transmittance of the CNF films were studied. Compared to the properties of the CNF film prepared with the soybean residue cellulose by high-pressure homogenization 15 times (HGT-15 film), the mechanical properties of the CNF film with soybean residue cellulose by decolorizing treatment decreased, but the light transmittance increased. The film prepared by adding HGT-15 CNF to whey protein was investigated for its mechanical property, light transmittance, and solubility. Unlike the pure whey protein film, addition of 2.0% CNF to the whey protein enhanced the mechanical property and water vapor transmission rate (WVT) of the film. With the increase in CNF content, the solubility of the whey protein film decreased, and then stabilized.     

再生蛋白纤维研究进展

再生蛋白纤维是一种性能优良,应用广泛的新型绿色环保材料,可分为再生植物蛋白质纤维与再生动物蛋白质纤维两大类。文章介绍了再生蛋白纤维的发展历程,以及以大豆蛋白、牛奶蛋白、玉米蛋白等为原料加工再生蛋白纤维的制备、性能及其应用,并对其今后的发展前景进行了展望。     

谷氨酰胺转移酶对大豆分离蛋白膜性能的影响

研究注模前酶作用时间对谷氨酰胺转移酶(TGase)改性大豆分离蛋白(SPI)膜性能的影响。在注模之前,将TGase(8U/g SPI)加入到成膜溶液中,分别在磁力搅拌下作用0、30、60、120min,然后注模成膜。利用质构仪检测蛋白膜的机械性能,结合哈克流变仪的动态黏弹实验及SDS-PAGE 实验进一步分析。注模前适度的酶作用(≤60min)在一定程度上有利于TGase 改性的SPI 膜机械强度的提高,特别是抗拉强度(TS)值;但是,时间不宜过长,因为注模前的酶作用也会诱导SPI 蛋白组分的聚沉反应,从而降低成膜溶液中可溶解蛋白的含量。结果表明,TGase改性SPI 膜时,一方面会诱导蛋白交联;另一方面,交联过多又会导致沉淀;在利用TGase 提高SPI 膜的机械性能时如何把握两者之间的关系,在交联的同时抑制酶促聚沉非常重要。     

酶法从全酯大豆中同时制备大豆油和大豆水解蛋白工艺的研究

研究了酶法从全脂大豆中同时制各大豆油和大豆水解蛋白的工艺，水提过程的最佳工艺条件为固液比１：１０，温度４４℃，ｐＨ７．７０和提取时间３６ｍｉｎ。含油大豆蛋白进行两次有控制的酶解，得到等电点可溶大豆水解蛋白（ＩＳＳＰＨ）和稳定性低的乳化油。确定了转相法破乳的工艺条件，从乳化油分离得到纯度较高的大豆油。水解蛋白和油的得率分别达到７４％和６６％。探讨了等电点或可溶大豆水解蛋白的功能性质及其在食品中的应用。     

甜瓜种子性状及甜瓜籽油中角鲨烯含量研究

采用气相色谱法等对黄色马泡瓜、包瓜等30个甜瓜品种角鲨烯含量进行测定。种子形态特征及相关性分析得知百粒重与面积比和角鲨烯含量均成极显著相关水平,但百粒重与面积比的极显著关系为负相关,即面积比越大,百粒重越小,而角鲨烯含量却随着百粒重的增加有所增加。这30个品种甜瓜籽油中角鲨烯的含量较高(641.7~2 858.3 mg/kg),经主成分分析表明,共有4个主成分对其贡献率较大。在此基础上进行聚类分析可以将其分为4类,其中第一、二类群,面积比和单个重量较小,但角鲨烯含量较高,第三、四类群则长/宽均值较大,角鲨烯含量较高。     

立地对油茶籽出油率及油茶籽油品质的影响研究

为了探明立地对油茶籽出油率及油茶籽油品质的影响,以9个立地的低温压榨油茶籽油为样品,测定油茶籽出油率及油茶籽油的理化性质、感官品质、脂肪酸组成、功能性成分含量及氧化诱导时间,分析坡向、坡位因子对油茶籽出油率及油茶籽油品质的影响。结果表明:立地对油茶籽出油率及油茶籽油的过氧化值、碘值、皂化值、感官品质、功能性成分含量及氧化诱导时间均具有明显影响,对油茶籽油的酸价、脂肪酸组成无明显影响。说明立地是影响油茶籽出油率及油茶籽油品质的重要因素。     

Development of a homogeneous competitive immunoassay for phosphorylated protein antigen based on the enhanced fluorescence resonance energy transfer technology

We describe a homogeneous competitive immunoassay for a phosphorylated protein antigen. The assay takes advantage of the enhanced fluorescence resonance energy transfer (FRET) technology, which has a unique characteristic that the FRET signal is increased by the specific interaction of two fluorolabeled leucine zippers. We chose extracellular signal-regulated kinase (ERK) as a model antigen and constructed two molecular probes in which either anti-phosphorylation site antibody or the antigen peptide was chemically conjugated to the enhanced FRET probes. While these molecular probes indicated sufficient FRET signal without antigen, they displayed a significant change in the fluorescent spectrum by mixing with phosphorylated antigens. With this competitive enhanced FRET immunoassay, a phosphorylated ERK concentration within the range from 15 nM to 250 nM could be determined. Because the assay is very simple, it would be applied to not only in vitro assay but also in vivo detection of protein phosphorylation.