732离子交换树脂法制备L-亮氨酸钙及其表征

主要讨论了利用732离子交换树脂制备L-亮氨酸钙的工艺条件。在静态实验法中,通过单因子实验,分别考察温度、氢氧化钠和亮氨酸的摩尔比、L-亮氨酸浓度、树脂量对交换率的影响规律,同时测定了25℃下的交换动力学曲线。结果表明:交换可在室温下进行;适宜的摩尔比为1∶1～1.3∶1;L-亮氨酸浓度应控制在0.3mol·L-1以下;适宜的树脂用量应满足树脂中的钙与溶液中亮氨酸的摩尔比为1∶2;交换的平衡时间为15min。同时对不同入口浓度和不同流速下,亮氨酸钠在固定床交换柱上的动态交换过程进行了研究。用红外光谱、热重差热分析对螯合物进行表征,其组成为｛Ca[NH2CHCH2CH(CH3)2COO]2｝·H2O。     

鸡蛋壳赖氨酸螯合钙的制备及其结构表征

为提高废弃鸡蛋壳的利用率,对鸡蛋壳赖氨酸螯合钙的制备工艺进行研究,并对其结构进行表征,以开发一种新型氨基酸生物钙制剂。本文以鸡蛋壳和L-赖氨酸为原料,赖氨酸螯合钙螯合率为指标,优化鸡蛋壳赖氨酸螯合钙的制备工艺。通过单因素试验和响应面试验,考察螯合反应时间、反应温度、溶液p H和L-赖氨酸与Ca Cl2摩尔比等因素对赖氨酸螯合钙螯合率的影响,优化确定最佳螯合工艺为:反应时间为49 min,反应温度为70℃,溶液p H为8.7,L-赖氨酸与Ca Cl2摩尔比为2:1。在此条件下,赖氨酸螯合钙螯合率为82.84%,较柠檬酸钙和谷氨酸钙螯合率分别高3.55%和1.72%。采用红外光谱、X衍射分析了鸡蛋壳赖氨酸螯合钙的结构,结果表明L-赖氨酸中的-NH2键和-COOH键均参与了螯合反应,L-赖氨酸中氨基上的N原子和羧基上的O原子均参与了反应,因此赖氨酸与钙形成了螯合物。     

以贝壳粉为钙源的复合氨基酸螯合钙制备工艺优化

以废弃贝壳制得贝壳粉作为钙源,采用水体系合成法同时制备L-组氨酸和L-精氨酸复合氨基酸螯合钙,以螯合率为指标,设计单因素试验与正交试验,考察复合氨基酸与贝壳粉的摩尔比、pH值、反应温度、反应时间等因素对螯合率的影响。结果显示最佳螯合条件：复合氨基酸-贝壳粉摩尔比为1∶1,反应时间为60 min,反应温度为50℃,溶液pH值为9,在此条件下得到的复合氨基酸螯合钙螯合率最高。为废弃贝壳粉的高附加值利用和复合氨基酸螯合钙的制备工艺提供新思路。     

复合L-氨基酸镁络合物合成的研究

以豆粕为原料,利用酶水解工艺制备复合L-氨基酸,将氯化镁与复合L-氨基酸螯合制备复合L-氨基酸镁。结果表明:豆粕酶水解最佳工艺条件为:固液比1∶25、pH8.5、加10%胰蛋白酶与8%植物蛋白酶、酶解时间4h,所得豆粕水解度为37.80%。复合氨基酸与氯化镁螯合的最佳工艺条件为:配位摩尔比3∶1、pH8.0、温度80℃、时间50min,此条件下螯合率为45.82%。经红外光谱分析,复合L-氨基酸与氯化镁之间存在螯合作用。     

以鸡蛋壳为钙源制备谷氨酸螯合钙工艺研究

本文运用响应面法和控制变量法对以鸡蛋壳为钙源的谷氨酸螯合钙制备工艺进行优化,探讨p H、摩尔比、温度、时间等因子对谷氨酸螯合钙的螯合率的影响。通过实验分析得出:p H、摩尔比、温度、时间对氨基酸螯合钙的螯合率均具有显著影响,其影响大小依次为摩尔比、p H、螯合温度、螯合时间;优化后的谷氨酸螯合率为63.88%,其最佳工艺条件为:蛋壳粉/谷氨酸比为1∶3;溶液p H7.0;螯合温度70℃;螯合时间60min。此优化工艺为禽蛋壳的深入研究及在食品领域中工业化生产创造了一定的条件。     

蚕蛹多肽螯合钙的生物可及性研究

补钙制剂在人体肠道环境中必须保持可溶状态,才可被吸收利用。以CaCO_3、葡萄糖酸钙为对照,利用体外模拟消化法测定蚕蛹多肽螯合钙在胃肠道环境中的可溶性钙含量,评价其生物可及性。结果发现,在模拟胃消化环境中,蚕蛹多肽螯合钙的可溶性钙释放率达90%以上;在模拟肠道消化环境中,其钙沉淀量显著低于CaCO_3、葡萄糖酸钙;在食物共存成分草酸、植酸、膳食纤维的影响下,其可溶性钙含量显著高于CaCO_3、葡萄糖酸钙。综合考虑,蚕蛹多肽螯合钙稳定性较好,生物可及性较高,具有补钙制剂开发的潜力。     

双酶解工艺制备复合L-氨基酸钙及生物利用的研究

本文采用胰蛋白酶、酸性蛋白酶和木瓜蛋白酶水解鸡骨和变性豆粕,制备复合L-氨基酸钙,并以SD大鼠为模型,评价该产品的生物利用率.结果表明复合L-氨基酸钙最适宜的螯合条件为复合L-氨基酸和钙浓度比为1∶2,在pH8.0,30min,70℃时钙的螯和率为22.73%,动物代谢实验表明复合L-氨基酸钙组和"乐力"氨基酸螯和钙组大鼠的股骨长度、股骨重量,钙吸收率、钙存留率和股骨钙的含量均高于对照组(P＜0.01).大鼠股骨钙的含量复合L-氨基酸钙组比"乐力"氨基酸螯合钙组有不同程度的增加(P＞0.05).由此可见复合L-氨基酸钙是一种高吸收型的活性钙.     

食源肽螯合钙的研究进展

钙是人体必需的营养物质,在生命健康中起着重要作用。钙摄入不足常会引发骨质疏松、佝偻病等诸多疾病。近年来随着越来越多的肽螯合钙从食物中制备出来,肽螯合钙稳定性好、生物利用度高等优点备受关注,它也在诸多研究中被视为一类理想的钙源补充剂。本文就食源性肽螯合钙的研究进展进行概述,介绍了肽螯合钙的制备及分离纯化方法,分析了影响其螯合能力的因素,并探讨了其促进钙生物利用度的方式,为肽螯合钙今后在功能性食品上的开发利用提供帮助。     

双酶解工艺制备复合L-氨基酸钙及生物利用的研究

本文采用胰蛋白酶、酸性蛋白酶和木瓜蛋白酶水解鸡骨和变性豆粕,制备复合L-氨基酸钙,并以SD大鼠为模型,评价该产品的生物利用率.结果表明复合L-氨基酸钙最适宜的螯合条件为复合L-氨基酸和钙浓度比为12,在pH8.0,30min,70℃时钙的螯和率为22.73%,动物代谢实验表明复合L-氨基酸钙组和"乐力"氨基酸螯和钙组大鼠的股骨长度、股骨重量,钙吸收率、钙存留率和股骨钙的含量均高于对照组(P＜0.01).大鼠股骨钙的含量复合L-氨基酸钙组比"乐力"氨基酸螯合钙组有不同程度的增加(P＞0.05).由此可见复合L-氨基酸钙是一种高吸收型的活性钙.     

响应面法优化海湾扇贝壳赖氨酸螯合钙的制备工艺

为提高废弃扇贝壳的利用率,对扇贝壳制备赖氨酸螯合钙的工艺进行研究。以海湾扇贝壳和L-赖氨酸为原料,在一定条件下制备赖氨酸螯合钙,考察了反应温度、时间、L-赖氨酸与Ca~(2+)摩尔比例和pH对螯合产率的影响。在单因素的基础上进行响应面实验,确定螯合工艺为:反应温度63.4℃,反应时间34.0 min,L-赖氨酸与Ca~(2+)摩尔比例2.1∶1,pH为8.4。在此最优条件下,获得的产品螯合产率为82.16%,螯合物中的钙含量为9.58%。傅里叶红外光谱显示钙离子与L-赖氨酸发生了螯合反应,形成了Ca-N键和Ca-O键,有赖氨酸螯合钙的生成。     

Effects of dietary leucine and phenylalanine on pancreas development,enzyme activity,and relative gene expression in milk-fed Holstein dairy calves

This study aimed to investigate the effect of dietary supplementation with leucine and phenylalanine on pancreas development, enzyme activity, and related gene expression in male Holstein calves. Twenty male Holstein calves [1 d of age, 38 ± 3 kg of body weight (BW)] were randomly assigned to 1 of the following 4 treatment groups with 5 calves in each group: control, leucine supplementation (1.435 g/L of milk), phenylalanine supplementation (0.725 g/L of milk), and leucine and phenylalanine (1.435 + 0.725 g/L of milk). The diets were made isonitrogenous with the inclusion of alanine in each respective treatment. The feeding trial lasted for 8 wk, including 1 wk for adaption and 7 wk for the feeding experiment. Leucine tended to increase the concentration of total pancreatic protein (mg/kg of BW). Phenylalanine increased the concentrations of plasma insulin, cholecystokinin, and pancreatic DNA (mg/g) and the expression of trypsin gene but decreased the pancreatic protein:DNA ratio and tended to decrease the pancreas weight (g/kg of BW). No differences were observed in total pancreatic DNA (mg/pancreas and mg/kg of BW), pancreatic protein (mg/pancreas), or activities of α-amylase, trypsin, and lipase. The relative expression levels of the genes encoding α-amylase and lipase did not differ among the 4 groups. The supplementation of both leucine and phenylalanine showed an interaction on the pancreas weight (g and g/kg of BW) and a tendency of an interaction on the pancreatic protein concentration (mg/g of pancreas and mg/kg of BW) and the plasma glucose concentration. Leucine tended to increase the size of the pancreatic cells, whereas phenylalanine tended to increase the number of pancreatic cells. However, neither AA affected the activities of the pancreatic enzymes of the calves. These results indicate that leucine and phenylalanine supplementation in milk-fed Holstein calves differentially affect pancreatic growth and development.     

Leucine aminopeptidase from Streptomyces hygroscopicus is controlled by a low molecular weight inhibitor

In culture filtrate of Streptomyces hygroscopicus a producer of polyketide antibiotics, a leucine aminopeptidase and its autogenous inhibitor were detected. The leucine aminopeptidase was purified 4573-fold with yield of 82% by combination of ion exchange and hydrophobic chromatography. The enzyme is monomeric with a molecular mass of 51 kDa determined by gel chromatography and 67 kDa determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Optimal activity was at pH 8.0 and 40 degrees C. The pI of leucine aminopeptidase is 8.2. The enzyme is strongly inhibited by 1,10-phenantroline, amastatin and dithiothreitol. Atomic absorption spectrometry indicated 2 mols of ion zinc per mol of enzyme. The enzyme is stable at up to 70 degrees C. Leucine aminopeptidase prefers leucine and methionine as N-terminal amino acids. Activity of leucine aminopeptidase is strongly modulated by an autogenous low-molecular weight inhibitor during fermentation, especially during periods of intensive antibiotic production.     

Effects of environmental factors on leucine catabolism by Carnobacterium piscicola

The metabolites from leucine degradation are involved in dry fermented sausage aroma. The catabolism of leucine by a strain of Carnobacterium piscicola was studied directly in the growth medium with 3H-labelled leucine to investigate the effect of five parameters: phase of growth, pH, oxygen, glucose and alpha-ketoisocaproic acid. Resting cells (RC) were also incubated with 3H-labelled leucine. The radioactive metabolites from leucine catabolism were analysed by high performance liquid chromatography (HPLC). At pH 5.4 and 7.2, the main metabolites detected were 3-methyl butanal, 3-methyl butanol and alpha-ketoisocaproic acid. At pH 6.5, the leucine catabolism was maximum and was characterised by a high production of 3-methyl butanoic acid. Leucine catabolism was most important during the exponential phase of growth. The addition of alpha-ketoisocaproic acid at 1%, glucose at levels of 0.5% to 2% and shaking of the growth medium increased leucine catabolism.     

离子交换法提取木瓜皮中果胶的动力学研究

以木瓜皮为原料,分别研究了离子交换树脂法和酸提法提取果胶的动力学模型,获得速率常数和表观活化能,经过有效性检验和模型预测能力验证,模型均能很好预测果胶提取的动力学过程。离子交换法提取果胶的活化能Ea为23.68kJ/mol,与酸提法获得的37.88kJ/mol相比明显降低,离子交换树脂法提取木瓜皮中果胶明显优于酸提法。在树脂用量为5%、料液比为1∶30(g/mL)、浸提液pH值为1.5条件下,离子交换树脂法提取木瓜皮中果胶的最佳浸提温度为80℃,动力学分析优化最佳结果,得Tmax=117.3min,果胶得率达17.47%,与试验结果相吻合。     

连续离子交换法分离L- 乳酸的工艺设计及优化

与传统固定床离子交换工艺相比,连续离子交换分离L-乳酸具有连续、稳定、高效等显著优点。本实验基于静态吸附和固定床离子交换实验结果,设计优化连续离子交换工艺,实现了L-乳酸经济、连续、高效分离。通过静态吸附实验,筛选出最优树脂为732树脂,可在1min内达到吸附平衡,吸附量达345.97mg/g;最佳解吸剂为0.5moL/L H2SO4溶液。通过固定床离子交换实验,确定最佳进料流速40mL/min、最佳高径比7.5:1、穿透时间21.5min,用0.5mol/L H2SO4溶液进行解吸,解吸率超过97%。通过连续离子交换实验,确定了交换区(1#～6#)、交换后水洗区(18#～20#)、再生区(12#～17#)、再生后水洗区(9#～11#)和产品顶水区(7#～8#)的最佳进料流速分别为40、40、140、35mL/min和20mL/min,且各出口浓度呈周期性稳定变化。     

Metabolism of leucine by the isolated perfused goat udder

Seven lactating goat mammary glands from 6 goats were perfused for several hours in the presence of [U-14C]L-leucine (4 experiments) or [2-3H; 1-14C]DL-leucine (3 experiments) and received adequate quantities of glucose, acetate and amino acids. Radioactivity in casein was mainly recovered in leucine and 90% of casein leucine was derived from free plasma leucine. About 64% of the leucine molecules were used for casein synthesis. Up to 12% of the molecules were channelled into lipid synthesis, while the remaining (up to 24%) were metabolized to CO2. From the 3H/14C ratio of casein and casein leucine, it was calculated that 70-80% of the leucine molecules were reversibly transaminated before their incorporation into milk protein. However, only 4-8% of the plasma leucine molecules were transaminated during passage through the udder. Different pools for oxidation and for protein synthesis may be present in the goat mammary gland.     

阴离子交换树脂分离酪蛋白糖巨肽工艺条件优化

采用离子交换树脂从乳清粉中分离酪蛋白糖巨肽(casein glycomacropeptide,CGMP),筛选适于分离CGMP的离子交换树脂并考察静态吸附过程中吸附pH值、吸附时间、缓冲液浓度等因素对CGMP分离效果的影响。乳清粉溶液在pH5.1时离心除杂后与201×4树脂混合,吸附条件为吸附pH3.9、吸附时间1h、缓冲液浓度0.02mol/L、洗脱液为0.5mol/L pH4.0的氯化钠溶液、洗脱时间4h;100g乳清粉利用此工艺条件可得1.45g唾液酸含量10.4%(以蛋白质计)的CGMP。该工艺方法分离过程简单、纯化效果好、唾液酸含量高,适用于工业化生产。     

SD3 离子交换树脂分离提取ATP 的研究

通过对SD3 离子交换树脂对ATP 动态吸附、洗杂和洗脱条件的考察,确定最适吸附条件为：样品溶液H 2.0,浓度8.25g/L,离子交换柱的高径比为10(装柱湿树脂80g),流速1.0ml/min;最优洗杂液为pH1.5 HC1＋ 0.05mol/L NaCl 的溶液;ATP 的最优洗脱液为pH12.0 NaOH+0.1mol/L NaCl 溶液,优洗脱速度为0.5ml/min。     

蔗糖水解制取结晶果糖技术研究

为提升制糖产业的综合效益,以白砂糖为原料开发附加值更高的结晶果糖,探讨用蔗糖原料制取高纯度结晶果糖的最优工艺方法.实验以高浓度蔗糖液(55％w/w)为原料,食品酸味剂柠檬酸为水解剂,通过蔗糖水解、脱色、阴阳离子树脂除盐,以钙型树脂分离、纯化果葡糖液,在常温下得到结晶果糖和结晶葡萄糖.实验优化蔗糖最佳水解工艺条件:水解温...     

碎米制备高果糖浆的工艺研究

研究碎米制备高果糖浆的工艺,主要对碎米葡萄糖异构化制取果葡糖液、钙型树脂分离果糖和葡萄糖获得高果糖浆的工艺进行优化。通过单因素和正交试验,得到制取果葡糖液的最优条件：异构酶加酶量9mg/g 碎米葡萄糖、pH7.5、反应温度70℃、反应时间35h;通过正交试验,得到树脂分离制取高果糖浆的最优条件：分离温度70℃、糖液体积分数20%、洗脱液流速4mL/min、进料量40mL。在优化条件下获取的高果糖浆果糖含量为89.64%。