胃蛋白酶对抗狂犬病毒IgY活性的影响

目的 观察抗狂犬病毒IgY经胃蛋白酶酶解24h后，抗体活性的变化。方法 高效价抗狂犬病毒IgY粗提后，经胃蛋白酶酶解，纯化，用ELISA及小鼠中和实验测其抗体活性。结果 获得单一IgY解片段并能够中和狂犬病毒。结论IeY经胃蛋白酶酶解24h仍保持其中和抗体的活性，为制备口服免疫制剂奠定基础。     

An immunoassay to assess lamb and kid rennets authenticity

The potential adulteration of kid or lamb rennet with calf rennet is of interest for some Protected Designation of Origin cheeses producers and those looking for a specific cheese typicality. The approach proposed here for the authentication of kid or lamb rennet is based on the immuno-detection of bovine pepsin possibly present in calf rennet in varying quantities. The developed immunoassay (indirect ELISA) used a monoclonal antibody (mAb) raised against bovine pepsin. This mAb was found to be specific as it didn't cross-react with the pepsin of animal species other than bovine (kid, lamb, pig) and with other milk-clotting enzymes (chymosin and microbial enzymes). Adulteration tests were conducted with kid and lamb rennets spiked with a wide range of calf rennet (from 0 to 100% v/v). The presence of bovine pepsin was detected at low levels down to 6 mg/L in kid and lamb rennets. Good linear relationships were obtained between added bovine pepsin concentration and the absorbance values over the range 1.25–120 mg/L. Results showed that indirect ELISA proved to be an interesting tool for testing rennets authenticity targeting bovine pepsin as an indicator of the bovine adulteration of kid and lamb rennets.     

Use of pepsin for collagen extraction from the skin of bigeye snapper (Priacanthus tayenus)

Extraction and some properties of pepsin-solubilised collagens from the skin of bigeye snapper (Priacanthus tayenus) were investigated. Addition of bigeye snapper pepsin (BSP) at a level of 20 kUnits/g of defatted skin resulted in an increased content of collagen extracted from bigeye snapper skin. The yields of collagen from bigeye snapper skin extracted for 48 h with acid and with BSP were 5.31% and 18.74% (dry basis), respectively. With pre-swelling in acid for 24 h, collagen extracted with BSP at a level of 20 kUnits/g of defatted skin for 48 h had a yield of 19.79%, which was greater than that of collagen extracted using porcine pepsin at the same level (13.03%). The skin collagen was characterised to be type I with no disulfide bond. Electrophoretic study revealed slight differences in molecular weight between acid-solubilised collagen and all pepsin-solubilised collagens. The molecular weights of α1 and α2 chains in acid-solubilised collagen were estimated to be 120 and 112 kDa, respectively, whereas α1 and α2 chains of pepsin-solubilised collagens had molecular weights of 118 and 111 kDa, respectively. The result suggested that these pepsin-solubilised collagens might undergo partial cleavage in the telopeptide region by pepsin treatment. The maximum transition temperature (T_max) of acid-solubilised collagen was observed at 32.5 °C, which was slightly higher than that of pepsin-solubilised collagens (by about 1 °C). Generally, all collagens were highly solubilised in the pH range of 2–5 and sharply decreased at the neutral pH. No changes in solubility were observed in the presence of NaCl up to 3% (w/v) and the decrease was more pronounced with increasing NaCl concentration.     

Antimicrobial activity of recombinant human lactoferrin from <Emphasis Type="Italic">Aspergillus awamori</Emphasis>, human milk lactoferrin and their hydrolysates

The antibacterial activity of human lactoferrin from milk (hLF), recombinant human lactoferrin from Aspergillus awamori (rhLF) and their hydrolysates obtained with pepsin was investigated against Escherichia coli O157:H7, Salmonella Enteritidis and Listeria monocytogenes. The minimum inhibitory concentrations (MIC) and the minimum bactericidal concentrations (MBC) were determined for all the bacteria and the proteins assayed. Taking into account the MICs found for both lactoferrins studied, we can say that they behave very similarly, except for L. monocytogenes for which rhLF was more active. We studied the effect that heat treatments exerted on the antibacterial activity of the two types of lactoferrin and the only heat treatment that had a negative effect on that activity was 85 °C for 10 min. The activity of hLF and rhLF in UHT milk and whey against E. coli O157:H7 and L. monocytogenes, was also assayed. Our results showed a reduction in the number of viable cells for both microorganisms when were incubated with rhLF or hLF, but this decrease was lower than in broth media.     

Legumin allergens from peanuts and soybeans: effects of denaturation and aggregation on allergenicity

Legumin proteins Ara h 3 from peanuts and glycinin from soybeans are increasingly described as important allergens. The stability of an allergen's IgE binding capacity towards heating and digestion is considered an important characteristic for food allergens. We investigated the effects of heating and digestion on the IgE binding of Ara h 3 and glycinin. Both proteins are relatively stable to denaturation, having denaturation temperatures ranging from 70 to 92 degrees C, depending on their quaternary structure and the ionic strength. Aggregates were formed upon heating, which were partly soluble for glycinin. Heating slightly decreased the pepsin digestion rate of both allergens. However, heating did not affect the IgE binding capacity of the hydrolyzates, as after only 10 min of hydrolysis no IgE binding could be detected any more in all samples. Peanut allergen Ara h 1, when digested under equal conditions, still showed IgE binding after 2 h of hydrolysis. Our results indicate that the IgE binding capacity of legumin allergens from peanuts and soybeans does not withstand peptic digestion. Consequently, these allergens are likely unable to sensitize via the gastro-intestinal tract and cause systemic food allergy symptoms. These proteins might thus be less important allergens than was previously assumed.     

Anionic Mucoadhesive Polymers as Auxiliary Agents for the Peroral Administration of (Poly)Peptide Drugs: Influence of the Gastric Juice

The incorporation of (poly)peptide drugs in mucoadhesive polymers is a promising strategy for their peroral administration. In this study, the protective effect of various polymers toward an artificial gastric fluid and the influence of an enteric coating on the adhesive properties have been investigated. Tablets containing 30 mg of carbomer (C934P), neutralized carbomer (NaC934P), or sodium carboxymethylcellulose (NaCMC), 0.1 mg of the model protein peroxidase, and 19.9 mg of mannitol were incubated at 37°C for 2.5 hr with a simulated gastric fluid with and without pepsin. All polymers—although anionogenic—displayed quick swelling behavior in the acid milieu, leading to an unintended protein release. Moreover, pepsin is capable of penetrating into the polymeric carrier systems, thereby rapidly degrading the embedded protein. Enteric coating, on the other hand, leads to strongly reduced adhesive properties. Only NaC934P tablets coated with polymethacrylate containing 9% triethylcitrate displayed no significant (p <. 05) reduction in adhesive strength. Results give essential basic information for the development of peroral (poly)peptide dosage forms based on mucoadhesive polymers.     

低pH胃蛋白酶-甲苯消化法灭活破伤风免疫血浆中脂包膜病毒效果验证

目的验证低pH条件下胃蛋白酶-甲苯消化法对不同核酸类型的脂包膜病毒的灭活效果。方法以水疱性口炎病毒(Vesicular stomatitis virus,VSV)作为RNA指示病毒,以伪狂犬病病毒(Pseudorabies virus,PRV)作为DNA指示病毒,将破伤风免疫血浆样品经低pH(3.2±0.2)、0.2%甲苯、6～12活力单位胃蛋白酶处理后各取27 ml,分别加入3 ml指示病毒(9∶1),在(30.0±1)℃水浴中分别振摇10、30、60、90 min灭活病毒。以Vero细胞、PK-15细胞为基质,采用96孔细胞病变法检测残余病毒滴度,验证病毒灭活效果。结果破伤风免疫血浆样品经低pH胃蛋白酶及甲苯消化处理90 min后,VSV和PRV两种指示病毒的灭活效果分别为3.12～3.88和5.25～5.38 logTCID50/0.1 ml。结论采用低pH胃蛋白酶-甲苯消化法对破伤风免疫血浆中PRV灭活效果较好,而对VSV灭活效果有待提高。     

Effects of tea polyphenols on the activities of α-amylase,pepsin, trypsin and lipase

Tea polyphenols (TP) possess many beneficial properties, such as reducing the risk of cancer and heart diseases, and acting as natural antioxidants for the food industry. At the same time, tea polyphenols might inhibit digestive enzymes and reduce food digestibility. To explore this possible antinutritional property, the effects of tea polyphenols on the activity of four typical digestive enzymes were investigated. HPLC analysis of the tea polyphenols extracted from Chinese green tea indicated that their catechin content was 93.6% (w/w), and that the content of ester bond-containing polyphenols was more than 82%. Measurement of the interaction of gelatin with tea polyphenols was first carried out, in order to model enzyme protein–TP interaction. It proved that tea polyphenols were capable of binding and precipitating protein, suggesting a potential ability of TP to denature digestive enzymes. In addition, the inhibitory effects of tea polyphenols on α-amylase, pepsin, trypsin and lipase were studied. In the presence of 0.05 mg/ml tea polyphenols, the inhibition ratios of α-amylase, pepsin, trypsin and lipase were, respectively, 61%, 32%, 38% and 54%, suggesting that TP might possess antinutritional properties.     

Effect of heat treatment on the antibacterial activity of bovine lactoferrin against three foodborne pathogens

The effect of different heat treatments on the antimicrobial activity of bovine lactoferrin against Escherichia coli O157:H7, Salmonella enteritidis and Listeria monocytogenes has been studied. We have observed that the heat treatments lower than 85°C for 10 min did not affect the antibacterial activity of the protein. Hydrolysates of bovine lactoferrin were found to be more active than the native protein against the three pathogens. Moreover, the antibacterial effect of bovine lactoferrin was also assayed in milk and whey, and although we found a reduction in the number of viable cells, this reduction was lower than in culture media.     

Effect of digestive enzymes on the activity of camel‐milk insulin

This study investigated the effect of digestive enzymes on the activity of camel‐milk insulin. The digestion was performed using the sequential action of pepsin and pancreatin. Proteolysis degree was estimated using the O‐phthaldialdehyde method. Insulin concentration was determined using an enzyme‐linked immunosorbent assay (ELISA). Results revealed that milk proteins were partially digested by pepsin alone and the degradation was increased during the pepsin–pancreatin digestion as compared to control. Insulin lost its activity after 30 min of pepsin digestion, and it was not detected by ELISA. This study strongly suggests that insulin is not responsible for the antidiabetic action of camel's milk.