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Enterococci are lactic acid bacteria (LAB) that play a role in the aroma formation, maturation, and sensory development of fermented foods such as meat and dairy products. They also contribute to the improvement of the extended shelf life of fermented foods by producing bacteriocin. The aim of this study was to isolate bacteriocin-producing LAB from sheep and goat colostrum, to characterize the bacteriocin-producing strains, and determine the technological properties of the strains. A total of 13 bacteriocin-producing LAB was isolated and identified as 11 Enterococcus mundtii and two Enterococcus faecium. The strains were found to be genetically different from each other by phylogenetic analysis of 16S rRNA gene sequences and random amplified polymorphic-DNA (RAPD-PCR). It has been determined that bacteriocins show activity in a wide pH range and are resistant to heat, lose their activity with proteolytic enzymes and α-amylase, but are resistant to detergents. While the presence of the munKS gene was detected in all of the strains, it was determined that E. faecium HC121.4, HC161.1, E. mundtii HC147.1, HC166.5, and HC166.8 strains contained multiple enterocin genes. Trisin-SDS-PAGE analysis revealed two active protein bands of approximately 5.1 and 5.5 kDa in E. faecium HC121.4 and one active protein band with a weight of approximately 4.96 kDa in other strains. E. mundtii strains and E. faecium HC161.1 were identified as mundticin KS producers, and E. faecium HC121.4 was defined as an enterocin A and B producer. Except for E. mundtii HC166.8, acid production of strains was found to be slow at 6 h and moderate at 24 h. None of them showed extracellular proteolytic and lipolytic activities. It was found that the strains had esterase, esterase lipase, leucine arylamidase, acid phosphatase, and naphthol-AS-Bl-phosphohydrolase activities, while protease activities were low and peptidase activities were high. In conclusion, bacteriocin producer 13 Enterococcus strains isolated from sheep and goat colostrum were found to have the potential to be included in starter culture combinations.

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Gram-negative diderm bacteria are characterized by a tripartite cell envelope, composed of an inner membrane (IM) and a lipopolysaccharide (LPS)-containing outer membrane (OM), separated by an aqueous space where the peptidoglycan is embedded. LPS is a peculiar glycolipid endowed with several biological activities. The biosynthesis and transport of LPS to its final location take place in every compartment of the cell envelope. Proteins and protein machineries with different subcellular localization are involved in this process to facilitate the trafficking of LPS across subcellular compartments that differ in their physicochemical proprieties. The fractionation of bacterial cell envelopes can give information on the status of the LPS biogenesis by allowing the analysis of LPS profiles and of the localization of proteins involved in the transport. Here, we describe a standardized protocol for membrane fractionation in Escherichia coli using sucrose density gradient centrifugation that separates the IM from the OM cellular fractions. Bacterial cells are first converted into spheroplasts and lysed; then the membrane fractions are collected by ultracentrifugation and separated at high speed by exploiting the differences in membrane density. The fractions obtained are analyzed for LPS total amount and electrophoretic profile.

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Sea cucumber (Stichopus japonicus) is a high-protein food with the potential to release certain peptides through enzymolysis. This work is to explore the characteristics of peptides released from Stichopus japonicus protein in the process of digestion. Hydrolysates were obtained by gastrointestinal digestion and fractioned to <3, 3-10, 10-30 and >30 kDa fractions. Fifty-eight peptides from <3 kDa fraction were characterized using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Hydrolysates could improve glucose uptake of 3 T3-L1 cells and high insulin-induced insulin-resistant Hep G2 cells. Molecular docking showed that the released peptides had similar binding mode with anagliptin, a dipeptidyl peptidase IV (DPP-IV) inhibitor. The <3 kDa fraction in gastro and intestinal digestion showed the greatest DPP-IV inhibitory potency (IC50 0.51 and 0.52 mg/mL, respectively). The results indicated that sea cucumber could be used as a functional food to release antidiabetic peptides through gastrointestinal digestion.

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@#To investigate the freshness, high molecular weight substances, the determination of polypeptide, haemolysis and agglomeration, biological activity of Cervus and Cucumis polypeptide injection; to provide the direction for improving the quality of products for enterprises; furthermore, to provide reference for the revision of the quality standards of Cervus and Cucumis polypeptide injection. Firstly, we investigated the factors affecting the freshness of the injection, including biogenic amines, aflatoxins, the acid value and peroxide value of the melon seeds. The method of dansyl chloride pre-column derivatization-HPLC was used to determine the content of 8 biogenic amines in Cervus and Cucumis polypeptide injection. The method validation results showed good specificity, precision, linearity and recovery rates, which was suitable for the determination of biogenic amines in Cervus and Cucumis polypeptide injection. The results of sample determination showed that relatively higher concentrations of cadaverine were detected in the products from company B. The results of aflatoxins, acid value and peroxide value showed that the melon seeds from some companies had rancidity, mildew and other problems, indicating that the quality standards of multi-component biochemical drugs containing animal- and plant-derived components should be controlled in terms of freshness. Secondly, the methods for the determination of high molecular weight substances and polypeptides in the quality standard were improved. Tricine-SDS-PAGE electrophoresis was used instead of gel chromatography to determine the high molecular weight substances, which improved the accuracy of determination. The kits were used instead of folin-phenol for the determination of peptide content, which is easy to operate, specific and suitable for high-throughput sample determination. Finally, the haemolysis, agglomeration, and biological activity of Cervus and Cucumis polypeptide injection were studied. The results showed that no haemolysis and agglomeration were found in all samples, and the inhibitory effect of samples on THP-1 proliferation in vitro from different companies was different to some extent. In conclusion, the optimized quality standard is more suitable for the detection of Cervus and Cucumis polypeptide injection, and can lay the foundation for improving the safety of multi-component biochemical drugs.

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BACKGROUND: Catheter-associated urinary tract infections are one of the most common types of hospital-acquired infections that start with bacterial adhesion and lead to biofilm formation. The antagonistic activity of lactic acid bacteria against pathogenic organisms makes them important for medical applications. OBJECTIVE: This study evaluated the precise method for purification of bacteriocin from Lactobacillus plantarum subsp. argentoratensis SJ33, and its characterization and effectiveness for biofilm inhibition on urinary catheters coated with bacteriocin. METHODS: Purification of bacteriocin was carried out using various methods such as cell adsorption-desorption, gel permeation chromatography, and hydrophobic interaction chromatography. Bacteriocin preparation was analysed using reverse-phase high-performance liquid chromatography (HPLC) and further characterised by Tricine SDS-PAGE and Q-TOF ESI MS. Antibacterial activity of bacteriocin was assessed against 16 different Gram-positive and Gram-negative bacterial strains, and their effect on morphology was observed under scanning electron microscopy (SEM). Biofilm adherence and inhibition were evaluated by crystal violet assay, fluorescence microscopy and SEM. RESULTS AND CONCLUSIONS: Bacteriocin preparation exhibited broad-spectrum activity against both Gram-positive and Gram-negative bacteria, and SEM analysis revealed membrane pore formation. On treating with various enzymes, bacteriocin was found to be sensitive to proteases, which confirmed its proteinaceous nature. Bacteriocin showed its applicability at acidic pH in the urinary tract. Antibiofilm activity of bacteriocin established its significance in catheter-associated biofilm inhibition against Pseudomonas aeruginosa and Staphylococcus aureus. Molecular weight of bacteriocins, namely Bac F1 and Bac F2 as resolved by RP-HPLC, was estimated to be 4039 Da and 1609 Da, respectively.

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Tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis (tricine-SDS-PAGE) is an efficient way of separating low molecular mass proteins. However, the standard system is quite complicated and specifically may not be useful when the separated proteins are to be recovered from the gel for quantitative analysis. Here, we describe a simplified system whereby these smaller proteins can be resolved in comparatively low percentage gels which have high compatibility with modern detectors such as UV and inductively coupled plasma-mass spectrometry (ICP-MS).

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Bacterial surface appendages of the type 4 pilus superfamily play diverse roles in adherence, aggregation, motility, signaling, and macromolecular transport. Here we describe two analytical approaches to study assembly of type 4 pili and of pseudopili produced by type 2 protein secretion systems: the shearing assay and immunofluorescence microscopy. These complementary antibody-based methods allow for semiquantitative analysis of fiber assembly. The shearing assay can be scaled up to yield crude extracts of pili that can be further analyzed by electron and atomic force microscopy or by mass spectrometry.

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Acquisition of host-derived proteins possessing key regulatory function is a hallmark of Borrelia burgdorferi, and an important step to successfully infect the human host, inhibiting activation of complement as innate immunity's first line of defense. Hence, the identification and characterization of interacting ligands is a prerequisite to gain deeper insights into the molecular principles of how spirochetes overcome the detrimental effects of complement. Far western blotting enables the detection of protein-protein interactions in vitro using cell lysates containing the prey proteins and purified complement proteins or human serum as a source for soluble complement proteins as bait proteins. Here, the methodology for the detection and characterization of Borrelia-derived proteins interacting with complement regulator Factor H is described, including the preparation of whole cell lysates, the separation of proteins by Tris-Tricine SDS-PAGE, the transfer of the proteins to nitrocellulose membranes, and the detection of Factor H-interacting proteins by Far western.

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The influence of high-intensity ultrasound (HIU) on the technofunctional properties and structure of jackfruit seed protein isolate (JSPI) was investigated. Protein solutions (10%, w/v) were sonicated for 15min at 20kHz to the following levels of power output: 200, 400, and 600W (pulse duration: on-time, 5s; off-time 1s). Compared with untreated JSPI, HIU at 200W and 400W improved the oil holding capacity (OHC) and emulsifying capacity (EC), but the emulsifying activity (EA) and emulsion stability (ES) increased at 400W and 600W. The foaming capacity (FC) increased after all HIU treatments, as opposed to the water holding capacity (WHC), least gelation concentration (LGC), and foaming stability (FS), which all decreased except at pH 4 for FS. Tricine sodium dodecyl sulfate polyacrylamide gel electrophoresis (Tricine-SDS-PAGE) showed changes in the molecular weight of protein fractions after HIU treatment. Scanning electron microscopy (SEM) demonstrated that HIU disrupted the microstructure of JSPI, exhibiting larger aggregates. Surface hydrophobicity and protein solubility of the JSPI dispersions were enhanced after ultrasonication, which increased the destruction of internal hydrophobic interactions of protein molecules and accelerated the molecular motion of proteins to cause protein aggregation. These changes in the technofunctional and structural properties of JSPI could meet the complex needs of manufactured food products.

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Objective To establish a simple and feasible method in analyzing the molecular weight distribution of peptides in thymosin.Methods Improved Tricine-SDS-PAGE electrophoresis was applied to detect the molecular weight of peptides and the content of thymosinα1 in thymosin.Results Tested the thymosin preparations on the domestic market using this im-proved method.It was demonstrated that the peptide molecular weight distribution in thymosin preparations was between 3.5~8.5 kD,also could detect the concentration of 1 μg thymosinα1 in thymosin by using this improved method.Conclusion This improved method is suitable for the analysis of peptides molecular weight distribution and the concentration of thy-mosinα1,so it can be used for control quality of thymosin preparations.

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The conjugation of polysaccharides to peptides is essential for antigen delivery and vaccine development. Herein, we show that tricine SDS-PAGE in combination with Coomassie Blue staining was adequate to determine the conjugation efficacy of a peptide (epitope 35-55 of myelin oligodendrocyte glycoprotein) to mannan. In addition, tricine SDS-PAGE and periodic acid-Schiff stains were able to monitor the redox state of mannan. Using the described protocol, more than 99.9% of a peptide containing five lysines at its N-terminus was confirmed conjugated to mannan.

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Recently, a growing number of macromolecules such as peptides and proteins have been formulated into various microbicide formulations for the prevention of sexually transmitted infections. However, a fast and reliable high-throughput method for quantitating peptide/protein in polymer-based microbicide formulations is still lacking. As a result, we developed and validated a reversed-phase high-performance liquid chromatography method for the quantitation of gp120 fragment and LL-37 simultaneously in various microbicide gel formulations. This method was capable of detecting a limit of linearity (regression coefficient of 0.999) for gp120 fragment and LL-37 within a range of 0.625-80 and 1.25-80 µg mL-1, respectively. The lower limit of quantification for gp120 fragment and LL-37 was 1.14 and 0.31 µg mL-1, respectively. Method validation demonstrated acceptable intra- and inter-day RSD % (<5 %) and accuracy (95.67-100.5 %). Formulating both peptides into polymeric pharmaceutical gel formulations showed high extraction efficiency (in the range of 95.90 ± 3.03 to 111.45 ± 2.51 %). Using this method, we were able to separate and identify the forced degraded products from both peptides simultaneously without affecting the quantitation of both peptides in the polymeric dosage forms. Furthermore, this method was able to detect and separate degradants that were unable to be revealed using gel eletrophoresis.

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Western blotting is a widely used technique for the detection and quantification of proteins and peptides. However, it is challenging to detect small peptides efficiently by the conventional Western blotting method with shaking, in part because the peptides readily detach from the blotted membrane. Although some modified Western blotting protocols have been developed to overcome this problem, it remains difficult to prevent peptide detachment from the membrane. In this study, we show that the previously developed vacuum-assisted detection method greatly improves the detection of small peptides without additional protocol modification. The vacuum-assisted method was developed to shorten the time required for all immunodetection steps, and all the Western blotting solutions penetrated the membrane quickly and efficiently by this method. By using this vacuum method, we succeeded in detecting small peptides that were completely undetectable by the conventional Western blotting method. We also confirmed that peptide detachment was induced even by gentle shaking in the case of the conventional method, and the detachment was accelerated when detergent was present in the buffer. Unlike in the conventional method, there is no need to shake the membrane in solution in the vacuum method. Therefore, it is thought that the small peptides could be detected sensitively only by the vacuum method.

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Objective:To develop an indirect enzyme-linked immunosorbent assay (ELISA) for semi-quantification of major allergen parvalbumin in fish.Methods:The soluble proteins were prepared from both white and dark muscles of seven species of freshwater fish and five species of marine fish.Tricine-SDS-PAGE and Western blot were performed to examine the protein patterns of fish muscle extracts.Natural parvalbumin being used to make calibration curve was purified from silver carp (Hypophthalmichthy molitrix) by ammonium sulphate fractionation,followed by ion exchange and gel filtration chromatography.The molecular mass of purified protein was estimated by Tricine-SDS-PAGE and identified by Western blot with anti-frog parvalbumin monoclonal antibody PARV-19.ELISA using PARV-19 was carried out to evaluate parvalbumin contents in white and dark muscles.Results:Tricine-SDS-PAGE revealed species-specific differences in proteins of heated extracts.Western blot confirmed that the major bands were showed in Tricine-SDS-PAGE with the molecular masses of 10-14 kD corresponded to parvalbumins recognized by PARV-19 and various numbers of isoforms of parvalbumin existed in different species of fish.There might be some differences in the parvalbumin contents and the epitope region was recognized by PARV-19 based on the differences in relative intensities of protein immunodetection.The ELISA showed that the contents of parvalbumin were 4 to 33 folds higher in the white muscle than in the dark muscle and varied greatly in different species of fish.Conclusion:These results validate that the dark muscle might be less allergenic than the white muscle due to the lower content of parvalbumins,and it is suggested that the commercial anti-parvalbumin antibody PARV-19 can be used to detect parvalbumins from the commercially important species of fish tested in this study and the method we develope succeeds to detect the major allergen in various species of fish.