Biopreservation of chocolate mousse with Lactobacillus helveticus 2/20: Microbial Challenge Test

Probiotic bacteria are used for food biopreservation because their metabolic products might contribute to ensuring food microbiological safety and/or increase its shelf life without the addition of chemical preservatives. Moreover, biopreserved foods are excellent vehicles for the delivery of probiotic bacteria. The aim of the study was to investigate the potential of chocolate mousse food matrix for the delivery of the probiotic strain Lactobacillus helveticus 2/20 (Lb. helveticus 2/20) and to investigate its capacity to inhibit the growth of two foodborne pathogenic bacteria (Staphylococcus aureus and Escherichia coli). Therefore, the populations of free or encapsulated in calcium alginate Lb. helveticus 2/20 cells and/or of each pathogen (used to voluntarily contaminate each sample) were monitored both in complex nutrient medium (MRS broth) and in chocolate mousse under refrigeration conditions and at room temperature. Lb. helveticus 2/20 alone in free or encapsulated state effectively inhibited the growth of Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923 in chocolate mousse when stored at 20 ± 2 °C. Practically no viable unwanted bacteria were identified on the 7th day from the beginning of the process. High viable Lb. helveticus 2/20 cell populations were maintained during storage under refrigerated conditions (4 ± 2 °C) and at room temperature. Chocolate mousse is thus a promising food matrix to deliver probiotic Lb. helveticus 2/20 cells, which could also protect it from contamination by unwanted bacteria

Uptake and subcellular distribution of radiolabeled polymersomes for radiotherapy

Polymersomes have the potential to be applied in targeted alpha radionuclide therapy, while in addition preventing release of recoiling daughter isotopes. In this study, we investigated the cellular uptake, post uptake processing and intracellular localization of polymersomes. Methods: High-content microscopy was used to validate polymersome uptake kinetics. Confocal (live cell) microscopy was used to elucidate the uptake mechanism and DNA damage induction. Intracellular distribution of polymersomes in 3-D was determined using super-resolution microscopy. Results: We found that altering polymersome size and concentration affects the initial uptake and overall uptake capacity; uptake efficiency and eventual plateau levels varied between cell lines;

Elucidating the Influence of Tumor Presence on the Polymersome Circulation Time in Mice

The use of nanoparticles as tumor-targeting agents is steadily increasing, and the influence of nanoparticle characteristics such as size and stealthiness have been established for a large number of nanocarrier systems. However, not much is known about the impact of tumor presence on nanocarrier circulation times. This paper reports on the influence of tumor presence on the in vivo circulation time and biodistribution of polybutadiene-polyethylene oxide (PBd-PEO) polymersomes. For thi

The evolution of bicontinuous polymeric nanospheres in aqueous solution

Complex polymeric nanospheres in aqueous solution are desirable for their promising potential in encapsulation and templating applications. Understanding how they evolve in solution enables better control of the final structures. By unifying insights from cryoTEM and small angle X-ray scattering (SAXS), we present a mechanism for the development of bicontinuous polymeric nanospheres (BPNs) in aqueous solution from a semi-crystalline comb-like block copolymer that possesses temperature-responsive functionality. During the initial stages of water addition to THF solutions of the copolymer the aggregates are predominantly vesicles; but above a water content of 53% irregular aggregates of phase separated material appear, often microns in diameter and of indeterminate shape. We also observe a cononsolvency regime for the copolymer in THF–water mixtures from 22 to 36%. The structured large aggregates gradually decrease in size throughout dialysis, and the BPNs only appear upon cooling the fully aqueous dispersions from 35 °C to 5 °C. Thus, the final BPNs are ultimately the result of a reversible temperature-induced morphological transition

Near-Field Scanning Optical Microscope Combined with Digital Holography for Three-Dimensional Electromagnetic Field Reconstruction

International audienceNear-field scanning optical microscopy (NSOM) has proven to be a very powerful imaging technique that allows overcoming the diffraction limit and obtaining information on a scale much smaller than what can be achieved by classical optical imaging techniques. This is achieved using nanosized probes that are placed in close proximity to the sample surface, and thus allow the detection of evanescent waves that contain important information about the properties of the sample on a subwavelength scale. In particular, some aperture-based probes use a nanometer-sized hole to locally illuminate the sample. The far-field radiation of such probes is essential to their imaging properties, but cannot be easily estimated since it highly depends on the environment with which it interacts. In this chapter, we tackle this problem by introducing a microscopy method based on full-field off-axis digital holography that allows us to study in details the three-dimensional electromagnetic field scattered by a NSOM probe in different environments. We start by describing the NSOM and holography techniques independently, and continue by highlighting the advantage of combining both methods. We present a comparative study of the reconstructed light from a NSOM tip located in free space or coupled to transparent and plasmonic media. While far-field methods, such as back focal plane imaging, can be used to infer the directionality of angular radiation patterns, the advantage of our technique is that a single hologram contains information on both the amplitude and phase of the scattered light, allowing to reverse numerically the propagation of the electromagnetic field towards the source. We also present Finite Difference Time Domain (FDTD) simulations to model the radiation of the NSOM tip as a superposition of a magnetic and an electric dipole. We finally propose some promising applications that could be performed with this combined NSOM-holography technique

IDENTIFICATION AND EXAMINATION OF SOME PROBIOTIC PROPERTIES OF A STRAIN FROM THE GENUS LACTOBACILLUS, ISOLATED FROM SPONTANEOUSLY FERMENTED YOGURT

The intake of probiotic microorganisms helps to restore and maintain the balance of the gastrointestinal microflora, which has a beneficial effect on the overall health of the individual. In order to be included in the composition of probiotic preparations or as starter cultures in the production of functional probiotic foods or beverages, newly isolated Lactobacillus strains must be identified and a number of probiotic properties must be demonstrated. Lactobacillus Pr2 isolated from spontaneously fermented yogurt was identified by physiological and biochemical (API 50 CHL) and molecular genetic (ARDRA-analysis and sequencing of the 16S rRNA gene) as a representative of the species Lactobacillus delbrueckii ssp. bulgaricus. The presence of some probiotic properties of Lactobacillus delbrueckii ssp. bulgaricus Pr2: resistance under model conditions of the gastrointestinal tract, antibiotic resistance profile, antimicrobial activity against pathogenic microorganisms and freeze-drying survival were examined. It was found that Lactobacillus delbrueckii ssp. bulgaricus Pr2 was highly sensitive to the effects of low pH values and the presence of enzymes (pepsin, pancreatin), to medium to high concentrations of bile salts in the medium (up to 1%), as well as to most of the antibiotics included in the study. However, the strain demonstrated high antimicrobial activity against pathogenic microorganisms and very good survival during the freeze- drying process. Lactobacillus delbrueckii ssp. bulgaricus Pr2 may be included in the composition of probiotics or as a starter culture for probiotic foods or beverages, but before that it is necessary to conduct additional research on the presence of other probiotic properties of the strain

ENTEROSAN PROBIOTICS: PROTECTING THE HEALTH OF MODERN MAN

ABSTRAC

Agricultural Academy

One of the requirements for a strain to be included in the composition of probiotic preparations is to exhibit antimicrobial activity against pathogenic microorganisms. The antimicrobial action of the strain Lactobacillus plantarum X2, isolated from naturally fermented sourdough, against pathogens is examined through co-cultivation of the Lactobacillus strain and each of the pathogens included in the study. The pathogenic microorganisms included in the present research are Escherichia coli ATCC 25922, Escherichia coli ATCC 8739, Salmonella abony NTCC 6017, Salmonella sp., Staphylococcus aureus ATCC 25293. It is observed that during separate cultivation of Lactobacillus plantarum X2 and each of the pathogens both Lactobacillus plantarum X2 and the pathogen accumulate high concentrations of viable cells. During co-cultivation Lactobacillus plantarum X2 maintains a high concentration of viable cells, while the number of living cells of the pathogen is reduced. The degree of reduction of the cells of the pathogen is strain specifi c and is partially due to the changes in the acidity of the medium as a result of the production of acids by Lactobacillus plantarum X2