双水相分离提取胃蛋白酶和琼脂糖的初步研究

以聚乙二醇/硫酸钠双水相体系分离提取琼脂糖和胃蛋白酶.结果表明:琼脂糖的回收率高于90%,胃蛋白酶的回收率约为50%,两者最适宜的分离条件为:pH值为3,Na2SO4浓度为0.4 g·mL-1,PEG10000的浓度为0.002 mol·L-1.     

冰乙酸和胃蛋白酶依次提取新鲜林蛙皮胶原蛋白

采用冰乙酸和胃蛋白酶依次对新鲜林蛙皮胶原蛋白进行提取.在冰乙酸提取过程中,首先通过控制单一因素变量对料液比、pH值、冰乙酸浓度、酸解时间和温度等5个因素对新鲜林蛙皮胶原蛋白提取率的影响进行研究,并采用正交实验考察林蛙皮胶原蛋白酸解提取的最佳工艺;其次,在冰乙酸提取的最优条件下,利用胃蛋白酶将酸解后的残余物进行再次酶解提取.实验结果表明,最佳酸解的工艺条件是:料液比为1∶30,pH为7.5,酸解时间为48 h,酸解温度为4℃,冰乙酸浓度为0.5 mol/L.在此工艺条件下,胶原蛋白的提取率为11.85％,胃蛋白酶对蛙皮残渣的提取率为5.25％,所得胶原蛋白的纯度为64.70％.     

壳聚糖固定胃蛋白酶的研究

以壳聚糖为载体、戊二醛为交联剂将胃蛋白酶固定化．戊二醛质量分数为5％，载体处理温度为30℃，胃蛋白酶与壳聚糖用量比为O．Ol，pH=4．O，固定12h以上，酶活性回收率达65％～70％。固定化酶最适温度为70℃，比游离酶提高了20℃；固定化酶最适pH值为3．O，而游离酶为2．O；固定化酶的表观米氏常数Km=3．32g／L，而游离酶Km=1．5lg／L。固定化酶重复使用3次时的酶活性回收率分别为73．9％，58．4％。42．6％。2个多月重复使用，活力未见明显下降。     

Effects of pepsin hydrolysis on the soy β‐conglycinin aggregates formed by heat treatment at different pH

The effects of pepsin hydrolysis on the β‐conglycinin aggregates formed by heat treatment at different pH were investigated. Results showed that fibrils were still observed, whereas the random aggregates were easily to be digested in the simulated gastric fluid. Electrophoresis and molecular weight analysis indicated that large aggregates still existed after pepsin treatment for fibrils. Hydrolysis resulted in changes in the apparent viscosity (ηapp) of 6% fibril solutions. The ηapp at the shear rate range (0–30 s^?1) increased in the order of fibrils < fibrils with pepsin for 60 min < fibrils with pepsin for 30 min. Smaller peptide/fibril fragments were generated, and additional aggregates were reformed during the hydrolysis process, as evidenced by thioflavin T and atomic force microscopy images. The native β‐conglycinin hydrolysates comprised a mixture of polypeptides enriched in about 47 kDa. These findings would provide valuable information about effects of enzymatic hydrolysis on plant oligometric globulin aggregates.     

Hydrolytic degree and antioxidant activity of purified casein characterised by different haplotypes (αs1-, β- and k-casein) after enzymatic hydrolysis with pepsin and enzymatic extract from Pleurotus eryngii

The aim of this study was to estimate the hydrolytic degree and antioxidant activity of purified casein characterised by different haplotypes (α_s1-, β- and k-casein) after in vitro digestion with two different enzymatic systems: pepsin from porcine gastric mucosa (EP) and a crude enzymatic extract from the edible mushroom Pleurotus eryngii. The used enzymes showed a different mode of casein catalysis with a consequent production of peptides of different antioxidant activity. The CN haplotype significantly influenced peptides production; in fact, the amino acid substitutions caused by genetic polymorphisms at the α_s1-, β- and k-CN loci influenced the sites of enzymatic cleavage and therefore the produced peptides. The above is evidenced by the different antioxidant activity found in the hydrolysates depending on the used enzymatic system, the CN haplotype, and the CN haplotype × enzymatic treatment interaction. The findings of this study are a perspective for the production of specific foods that exert a biological effect in addition to the nutritional one.     

Application of ultrafiltration to the preparation of defined hydrolysates of bovine haemoglobin

Many uses of protein hydrolysates have been developed and applied to areas such as nutritional therapy, culture media, and the isolation of biologically active peptides. All these applications need carefully controlled and characterized hydrolysates. In order to produce such a type of hydrolysate, it is possible to use haemoglobin which is a very well defined and constant protein source. Enzymic hydrolysis of haemoglobin by pepsin was carried out at pilot-plant scale in an ultrafiltration reactor with mineral membranes. The object was to obtain a reproducible, decolorized, salt-free enzymic hydrolysate. Two types of membranes were tested having 10000 dalton (M5 type) and 20000 dalton (M4 type) cut-offs. Little significant difference was observed in the final products when both types of membranes were used. Reproducibility of hydrolysates was verified by amino acid analysis and gel filtration chromatography. The haemoglobin hydrolysates produced contained more than 90% protein and are especially suitable for fine applications.     

酶解花生蛋白影响Fe2+吸收利用的体外实验研究

以花生蛋白经模拟胃液和胰液消化所得的消化物为研究对象,研究酶解花生蛋白对Fe2 生物效价的影响。结果表明,随Fe2 浓度的增加,花生蛋白模拟消化物与Fe2 的结合量下降,且随着时间的延长而降低;酶解花生蛋白能保护Fe2 不易被氧化为Fe3 ;Ca2 的加入能降低酶解花生蛋白与Fe2 的结合量。     

Acid‐formed pectin gel delays major incomplete kiwi fruit allergen Act c 1 proteolysis in in vitro gastrointestinal digestion

BACKGROUND: It is thought that food sensitisers must be able to reach the intestine in order to sensitise patients. Pectin is a gel‐forming plant polysaccharide that can protect allergens from in vivo gastric digestion and in vitro pepsin digestion. The aim of this study was to examine if pectin gel formed in the acidic environment of the stomach can protect labile allergen from in vitro gastrointestinal digestion. RESULTS: Pectin forms a gel in the acidic conditions of gastric fluid up to a concentration of 1.0 ± 0.14 g L^?1. Four allergenic fruits (kiwi, cherry, apple and banana) form gels in the same manner at the dilutions 14.8 ± 0.4; 8.4 ± 0.2, 9.4 ± 0.35 and 29.1 ± 0.2, respectively. The time necessary for dissolution of 50 g L^?1 pectin gel in intestinal fluid was found to be 70 ± 0.2 min. Pectin gel formed in situ was able to protect Act c 1 from pepsin digestion for 1 h and from further intestinal digestion for one additional hour. CONCLUSION: Pectin gel in an acidic environment protects Act c 1 from pepsin digestion and dissolves slowly in the slightly basic environment of the intestine allowing the survival of fruit allergen for additional time and possible interaction with the gut immune system. Copyright © 2008 Society of Chemical Industry     

酪蛋白水解肽对家兔细胞因子的影响

为了探索酪蛋白水解肽对家兔血清中IL-1β、IL-6、IL-12、IFN-γ、TNF-α、IL-1ra、IL-4、IL-10、TGF-β细胞因子的影响,采用胰蛋白酶水解得到酪蛋白水解物溶液,经超滤后得酪蛋白水解肽。将所得水解多肽以3种方式(口服、腹腔注射、耳静脉注射)对家兔给药,分别在给药3、2、2h后,用ELISA试剂盒测定血清中IL-1β、IL-6、IL-12、IFN-γ、TNF-α、IL-1ra、IL-4、IL-10、TGF-β细胞因子的浓度。结果表明,各种作用方式IL-4、IL-6、IL-10、TNF-α、TGF-β在家兔体内的含量都明显上升,但腹腔注射酪蛋白水解多肽较其他方式作用明显,而IL-1β、IL-1ra、IL-12、IFN-γ的含量降低,最明显的作用方式为腹腔注射,说明酪蛋白水解肽通过肠黏膜系统对细胞因子网络起着重要的调节作用。从给药途径看,腹腔注射的作用效果最为显著,其次是静脉注射,口服灌胃虽达到显著水平,但变化相对较小。说明酪蛋白水解肽主要是通过肠黏膜发挥作用,可通过制备肠溶性保健食品调节人体亚健康,同时为营养组学得研究奠定基础。     

酪蛋白酶解物的分离及其抗氧化活性

采用胃蛋白酶和胰蛋白酶(P+T)先后连续水解酪蛋白,采用001阳离子交换树脂分离该酶解液得到多肽;以酪蛋白的单一胃蛋白酶(P)和单一胰蛋白酶(T)酶解液为对照,系统评价酪蛋白不同酶解液及分离所获得的酪蛋白多肽的抗氧化活性。结果表明,阳离子交换树脂对(P+T)酶解液具有较好的分离作用,洗脱曲线共有4个峰,分别为P1、P2、P3、P4,收集冻干制得4个多肽。抗氧化性评价显示,P1、P2、P3、P4的还原力和DPPH自由基清除能力远高于未经分离的P、T和(P+T)酶解液。多肽P4表现出极高的Fe2+螯合能力,螯合率高达94.95%;P、T和(P+T)酶解液的Fe2+螯合力相当,螯合率达31%~33%,而P1、P2、P3不具备Fe2+螯合能力。在脂质过氧化抑制方面,P酶解液表现出较好的抑制力,其次为T酶解液,多肽P1、P2、P3、P4及(P+T)不具有脂质过氧化抑制力。由此可见,(P+T)连续水解液经阳离子交换树脂分离可制备具有较高自由基清除力及Fe2+螯合力的肽段,研究结论可为酪蛋白抗氧化肽的制备及分离提供参考依据。