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Lactobacillus casei is a Gram positive lactic acid bacterium used in dairy fermentations and present in the normal human gut microbiota. Certain strains are recognized as probiotics with beneficial effects on human and animal health. L. casei BL23 is a potential probiotic strain endowed with anti-inflammatory properties and a model strain widely used in genetic, physiological and biochemical studies. A number of bacterial cell surface polysaccharides have been shown to play a role in the immune modulation activities observed for probiotic lactic acid bacteria. In the present work, we purified the most abundant carbohydrate polymer of L. casei BL23 cell wall, a neutral wall polysaccharide (WPS) and established its chemical structure by periodate oxidation, methylation analysis and 2D NMR spectroscopy. The WPS of L. casei BL23 was shown to contain α-Rha, α-Glc, β-GlcNAc and β-GalNAc forming a branched heptasaccharide repeating unit (variant 1) with an additional partial substitution with α-Glc (variant 2). A modified non-reducing end octasaccharide, corresponding to a terminal unit of the WPS (variant 3), was also identified and allowed to define the biological repeating unit of the WPS. To our knowledge, this is the first report of the identification of a biological repeating unit based on a chemical evidence, in a cell wall polysaccharide of a Gram positive bacterial species., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

L-Lactic acid (L-LA) is one of the microbial products with several applications and its production efficiency is so important. In the present study, we have been exploring application of low intensity ultrasound technology to improve the metabolic activity for L-lactic acid production by Lactobacillus casei in different mediums. L-LA, biomass production and substrate (protein) consumption were measured as parameters of fermentation yield. L-LA and protein contents were determined using the titratable acidity and the biuret method respectively. Spectrophotometry (OD600nm) was used for measuring cell growths. L-LA, biomass production and protein consumption considered as dependent variables, but the amplitude of waves (20%, 40% and 60%), waves duration (15, 30, 45 s) and add of peptone (2, 6 and 10 g/l) as independent variables. The results showed that L-LA, biomass production and substrate consumption significantly increased (≈25%). Optimum conditions for biomass production was amplitude of 60%, 15s exposure time and 10 g/l peptone, while for acid lactic production and substrate consumption was 40%, 30s and 6g/l peptone, respectively. Flowcytometry analysis also showed that sonication led to increasing cell membrane permeability. This observation shows low intensity ultrasound as a potential parameter in the improvement of metabolic activity of L. casei., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The aim of the current study was to investigate the effect of varying sodium chloride concentrations (0-5%) on viability and membrane integrity of three probiotic bacteria, Lactobacillus acidophilus, Lactobacillus casei and Bifidobacterium longum, using conventional technique and flow cytometry. Double staining of cells by carboxyfluorescein diacetate (cFDA) and propidium iodide (PI) enabled to evaluate the effect of NaCl on cell esterase activity and membrane integrity. Observations from conventional culture technique were compared with findings from flow cytometric analysis on the metabolic activities of the cells and a correlation was observed between culturability and dye extrusion ability of L. casei and B. longum. However, a certain population of L. acidophilus was viable as per the plate count method but its efflux activity was compromised. Esterase activity of most bacteria reduced significantly (P < 0.05) during one week storage at NaCl concentrations greater than 3.5%. The study revealed that L. casei was least affected by higher NaCl concentrations among the three probiotic bacteria, as opposed to B. longum where the cF extrusion performance was greatly reduced during 1 wk storage. The metabolic activity and salt resistance of L. casei was found to be highest among the bacteria studied., (Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.)

Cell fractions including heat-treated cells, crude cell walls, intracellular extracts and exopolysaccharides (EPSs) obtained from Lactobacillus casei 01 were first studied for their effects on the proliferation of human intestinal epithelial cells, intestine 407 and the human colon cancer cell, HT-29. Their effects on the cytotoxicity of 4-nitroquinoline 1-oxide (4-NQO) against intestine 407 were further investigated. The results revealed that EPS exhibited the highest antiproliferation activity on HT-29 cells while the viability of intestine 407 cells was not affected by EPS at a concentration of 5-50μg/mL. It was also noted that all the cell fractions and EPS from L. casei 01 reduced the cytotoxicity of 4-NQO against intestine 407 with EPS showing the highest anticytotoxic activity. Additionally, it was found that EPS might exert blocking and bioanticytotoxic effects by both adjusting the function of intestine 407 and repairing the 4-NQO-damaged cells, thus reducing cytotoxicity of 4-NQO., (Copyright © 2011 Elsevier B.V. All rights reserved.)

The purpose of this research was to investigate the influence of sucrose at 2.0, 4.0, and 8.0% as a protectant during freeze-drying on the viability and membrane properties of Lactobacillus casei Zhang. Membrane properties were determined using zeta potential, hydrophobicity, fluidity, and integrity before and after freeze-drying. Exposing L. casei Zhang to sucrose protected it from drastic changes in cell surface electrophoretic mobility and hydrophobicity in contrast with the untreated condition, and the effect was dose related. Sucrose caused an increase in membrane fluidity compared with the control sample. Moreover, 2.0% sucrose decreased the general polarization values less than 4.0 or 8.0% sucrose, while 4.0% sucrose and 8.0% sucrose had no significant difference in decreasing general polarization values (P < 0.05). L. casei Zhang freeze-dried in the presence of 2.0% sucrose retained up to 23.7% membrane integrity, whereas cells freeze-dried with 4.0 and 8.0% sucrose had 32.4 and 37.6% membrane integrity compared with that of L. casei Zhang before freeze-drying. Correspondingly, the number of survivors of L. casei Zhang, determined by the plate count method, decreased from 8.02 to 0.63 log CFU/ml after freeze-drying in the absence of sucrose. However, in the presence of 2.0, 4.0, and 8.0% sucrose, the numbers of survivors were 2.01, 2.87, and 3.20 log CFU/ml after freeze-drying, respectively. The present work suggested that sucrose was an effective membrane protectant at 2.0, 4.0, or 8.0% on the surface zeta potential, hydrophobicity, fluidity, and integrity of L. casei Zhang.

We investigated the effects of transients in elution chemistry on bacterial desorption in water-saturated porous media. Two typical Gram-positive bacterial strains of Lactobacillus casei and Streptococcus mitis were used as the model bacteria in this research. These two strains were first deposited in the porous medium, after which the medium with deposited bacteria was flushed with rhamnolipid biosurfactant solutions with a step increase in concentrations, and pulse-type bacterial releases were obtained. Bacterial desorption was quantified from bacterial breakthrough curves. It was found that bacterial retention in silica sand corresponded to bacterial interaction free energies with silica sand evaluated at the equilibrium distance, which were calculated based on independently determined bacterial, sediment and solution surface thermodynamic properties. With the increase in rhamnolipid biosurfactant concentrations, interactions between bacteria and silica sand decreased, and consequently less bacteria were retained. The decrease in interactions between bacteria and silica sand with increasing rhamnolipid biosurfactant concentrations was attributed to a decrease in the solution electron acceptor parameter of the Lewis acid/base component of surface tension, gamma3+. The increase in rhamnolipid biosurfactant concentrations favored the decrease in solution gamma3+, and consequently decreased the interactions between bacteria and silica sand.

NO in vivo has both beneficial and nonbeneficial effects depending on site and concentration. Peroxynitrite, resulting from the reaction of NO with superoxide radical, causes cellular damage. Nitrotyrosine, end product of NO's toxic effects on cellular proteins, is a stable compound that can be used to detect evidence of harmful quantities of NO. We sought to detect nitrotyrosine in coronary arterioles of DBA/2 mice injected intraperitoneally with Lactobacillus casei cell wall. The inflammatory response induced occurred in perivascular fashion and involved mainly macrophages. It was variable according to time points, being severe on days 10 and 14 and mild to moderate on days 3 and 7. Few basal inflammatory cells appeared in controls injected with phosphate-buffered saline. Western immunoblots of homogenized hearts on days 10 and 14 demonstrated specific nitrated proteins. Immunohistochemistry of frozen sections of diseased hearts showed positive immunoreactivity for nitrotyrosine in coronary arterioles at the same time points. These findings were absent in the controls. We also determined the expression of inducible nitric oxide synthase (iNOS) in controls on days 10 and 14. iNOS colocalized with nitrotyrosine in perivascular macrophages and coronary arterioles of treated mice. Additionally, aneurysms were found on day 10 and intracardiac hemorrhage with consequent death on day 14. These observations supply evidence that NO through its reactive product, peroxynitrite, and its antigen/tissue marker, nitrotyrosine, is directly involved in coronary arteritis and aneurysm development in mice models of Kawasaki disease (KD). This article shows that macrophages are central to this and bolsters the likelihood of L. casei being the cause of KD.

The involvement of toxic oxygen intermediates in the bacteriostatic effects of mycotoxins (T-2 toxin, deoxynivalenol, ochratoxin A, aflatoxin B1, and fumonisin B1) was investigated by producing bacterial growth curves using turbidimetry assays in the presence and absence of oxygen radical-scavenging substances. The strains used in this study included Escherichia coli (FT 101), Streptococcus agalactiae (FT 311, FT 313, FT 315), Staphylococcus aureus (FT 192), Yersinia enterocolitica (FT 430), Salmonella infantis (FT 431), Erysipelothrix rhusiopathiae (FT 432), Lactobacillus plantarum (FT234) and Lactobacillus casei (FT 232). Tamoxifen, melatonin, l-carnitine and coenzyme Q10 were used as radical scavengers against oxygen toxicity to the strains studied. Tamoxifen was the most effective in inhibiting bacterial growth when used at a high concentration, whereas melatonin and l-carnitine were less effective. A combination of l-carnitine and coenzyme Q10 provided better protection against oxygen toxicity caused by the mycotoxins growth than they did individually. It was concluded that oxygen radicals are involved in the killing of bacteria and that there is endogenous formation of toxic oxygen products by mycotoxins. The objective of this study was to determine whether the antioxidants were able to counteract the toxic effects of the mycotoxins. The data obtained indicate that bacterial growth can be inhibited especially by T-2 toxin, aflatoxin B1 and ochratoxin A and that this effect can be partially counteracted by antioxidants such as coenzyme Q10 plus l-carnitine., (Copyright 1998 The Italian Pharmacological Society)