Svetla Danova - Academia.edu (original) (raw)

Papers by Svetla Danova

Microorganisms, Apr 4, 2024

Acta microbiologica Bulgarica, May 31, 2023

The present review summarizes research on the antimicrobial properties of modified natural zeolit... more The present review summarizes research on the antimicrobial properties of modified natural zeolite clinoptilolite. The modification of the clinoptilolite is based on its ion exchange features with silver, copper, zinc, or other ions in order to obtain antimicrobial properties. The review includes recent data on pretreatment and preconditioning to increase the effectiveness of ion exchange procedures and obtain a functionalized zeolite. The review covers antibacterial, antifungal, antiviral properties on natural zeolite clinoptilolite.

Carbohydrate Polymers, 2010

The structural characterization of purified Hyriopsis cumingii polysaccharides (HCPS) were studie... more The structural characterization of purified Hyriopsis cumingii polysaccharides (HCPS) were studied by using periodic acid oxidation, Smith degradation, methylation combined with HPLC, GC, GC–MS, FTIR and NMR spectra. Results showed that sugar rings of purified HCPS were pyranose rings. In HCPS-1 and HCPS-2, glycosyl residues were linked mainly by α-configuration glycosidic bond. As to HCPS-3, sugar residues were connected by

Case Studies in Construction Materials

Journal of Basic Microbiology, Aug 1, 2008

Lactobacillus plantarum strains were isolated from fully ripened, white brined Bulgarian home‐mad... more Lactobacillus plantarum strains were isolated from fully ripened, white brined Bulgarian home‐made cheeses. Strains were derived from phenotypically homogenous Lactobacillus group and were identified as L. plantarum based on both phenotypic and molecular identification (species‐specific and multiplex PCR) methods. Heterogeneity of L. plantarum isolates was evaluated by Rep‐PCR analysis.Further antimicrobial activity, antibiotic susceptibility and transit tolerance of the strains were evaluated. Most of them showed broad spectrum of activity against Gram‐negative bacteria (including human pathogens) independent on the presence of organic acids or hydrogen peroxide.All strains were sensitive to amoxicillin and sulfamethoxazole/trimethoprim, resistant to clinically relevant β ‐lactame antibiotics (penicillin and ampicillin) and to nalidixic acid, ciprofloxacin, streptomycin, and vancomycin. Significant variability in the sensitivity to tetracycline was noted.The tolerance to low pH, bile salts, pepsin and pancreatin at concentrations similar to those in the gastrointestinal tract was strain‐dependent. The exposure to bile salts was less destructive than exposure to pH 2.0 for all tested strains. Based on their combined responses to the above selection criteria, four L. plantarum strains, RL29, RL34, RL36 and RL37, were selected as potential probiotics for in vivo studies. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Folia Microbiologica, Dec 1, 2002

The production of a novel broad-spectrum antimicrobial peptide enterococcin A 2000, active agains... more The production of a novel broad-spectrum antimicrobial peptide enterococcin A 2000, active against Gram-positive and Gram-negative microorganisms including Listeria subsp, and Escherichia coli, by Enterococcusfaecium strain A 2000 isolated from the surface of traditional Bulgarian yellow cheese "kashkaval" is considerably influenced by complex nitrogen sources in the production medium. Medium components, especially peptone and yeast extract, and their concentration contributed to the increase in bacteriocin production during the stationary phase (16-46 h) of cultivation even in the absence of one of the components present in the basal cultivation MRS medium. Lactic acid bacteria (LAB) are economically important since they are largely used in food and feed fermentation. They produce different substances with antimicrobial activity which can be used as biopreservatives (Centeno et al. 1996). LAB are present in numerous food products and they are essential in many food transformation processes leading to changes in texture, flavor, and storage of fermented products. The ability of LAB to inhibit the growth of other bacteria has been known for many years; substances responsible for this antagonistic activity include organic acids, biacetyl, hydrogen peroxide, enzymes, defective phages, lytic agents, and bacteriocins (Tagg et al. 1976; Laukov~ et al. 1999; Laukovfi and Marekov~i 2001). Enterococci are Gram-positive bacteria fitting within the general definition of LAB. Modern classification methods prompted the transfer of some members of the genus Streptococcus, viz. some of the Lancefield's group D streptococci, to the new genus

Journal of Probiotics & Health, Nov 15, 2013

Food Science, Engineering and Technologies 2009, Plovdiv, Bulgaria. 23-24 October, 2009., 2009

Biotechnology & Biotechnological Equipment, 2009

Lactic acid bacteria play a key role in human health. These friendly bacteria as a part of the mi... more Lactic acid bacteria play a key role in human health. These friendly bacteria as a part of the microflora of the gastrointestinal tract (GIT) have a beneficial influence on microbial balance. The probiotic cultures stimulate the growth of beneficial microorganisms, crowd out potentially harmful bacteria and reinforce the body's natural defense mechanisms. Recent data improve the positive effects of probiotics and stimulate research for discovering of new lactic acid bacteria strains with probiotic properties. In present work the probiotic potential of 23 strains lactic acid bacteria, isolated from Bulgarian rye sourdoughs from different geographical regions was studied in vitro. Their affiliation to the genus Lactobacillus and Pediococcus was determined by classical phenotyping methods. Screening of the strains at selecting factors high acidity and different concentrations of bile salts was first accomplished. In addition, susceptibility to antibiotics, production of hydrogen peroxide and spectrum of antimicrobial activity were determined. After primary selection, 8 strains were chosen and they were tested in a model system for in vitro simulation of the conditions into the human GIT. As a result, two strains with high probiotic potential were found.

International Journal of Dairy Technology, May 1, 2005

ABSTRACT Koumiss is a slightly alcoholic fermented milk beverage, originally obtained by using na... more ABSTRACT Koumiss is a slightly alcoholic fermented milk beverage, originally obtained by using natural mix starters (lactic acid bacteria and yeast). Seven Lactobacillus strains from lyophilized koumiss were isolated and identified as L. salivarius, L. buchneri and L. plantarum. The process of lactic acid fermentation caused by koumiss strains was faster (9–13 h) than that with other lactobacilli. The conversion ratio of glucose to lactic acid ranged from 47% to 79% and was strain dependent. All strains were resistant to low pH. Three of the strains isolated were viable during prolonged cold storage in fermented milk (3 weeks at 4°C).

Biotechnology & Biotechnological Equipment, 2001

ABSTRACT Calcium binding protein from Streptomyces hygroscopicus 155 has been purified to electro... more ABSTRACT Calcium binding protein from Streptomyces hygroscopicus 155 has been purified to electrophoretic homogeneity. The isoelectric point of 4.89 is slightly less acidic than that from eukaryotic origin. The amino acid composition is typical of already studied bacterial calmodulins with the exception that trimethyllysine is absent.

Biotechnology & Biotechnological Equipment, 2011

Adhesion of lactic acid bacteria (LAB) to mucosal surfaces and their ability to prevent pathogeni... more Adhesion of lactic acid bacteria (LAB) to mucosal surfaces and their ability to prevent pathogenic invasion of the epithelium are among the most beneficial properties of probiotic lactobacilli. The molecular mechanisms of lactobacillus adhesion have not been fully studied and understood yet. Therefore, a current task is to reveal the genetic and biological factors that determine the adhesion of probiotic LAB cultures. A dairy product originating strain AC131 was selected for the present study, based on its broad-spectrum antimicrobial activity. It was identified as Lactobacillus plantarum by 16S rDNA sequence analysis. The presence of genes Map, Mub and EF-Tu, as genetic determinants of the adhesion factors in Lactobacillus plantarum AC131, was established by PCR analyses. In addition, in vitro tests for adhesive ability of the strain AC131 were carried out. Positive results in tests with two different cell lines were obtained and the strain AC131 was classified as strongly adhesive to HeLa and moderate adhesive to HT-29 cell line. Our results provide a promising basis for further characterization of Lactobacillus plantarum AC131, as a potential probiotic.

Life

Background: The accumulation of data on beneficial biological effects of probiotics and their met... more Background: The accumulation of data on beneficial biological effects of probiotics and their metabolic products favors their potential use in the prevention and treatment of various malaises. Methods: Nine postmetabolites from Lactic acid bacteria (LAB) of human or dairy origin and their antiviral activity were studied using the cytopathic effect inhibition test. The virucidal capacity, their influence on the adsorption stage of Koi herpes virus (KHV) and their preventive role against subsequent viral challenge on intact Common carp brain (CCB) cells were also determined by titration assay. Residual viral infectivity in postmetabolites-treated samples was compared to mock-treated controls and Δlgs were calculated. Results: When administered during KHV replication, the microbial products isolated from Lactiplantibacillus plantarum showed remarkable activity with a selectivity index (SI) between 26.5 and 221.4, as those effects were dependent on the sample-virus incubation time. Post...

BULGARIAN JOURNAL OF VETERINARY MEDICINE

Lactic acid bacteria (LAB) may contribute to the food safety. In the present study, the antagonis... more Lactic acid bacteria (LAB) may contribute to the food safety. In the present study, the antagonistic activity of 45 Bulgarian Lactobacillus homo- and heterofermentative strains of human and dairy origin, and 4 multibacterial formulas against Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) was assessed. In vitro tests were performed in different model systems - milk, soymilk, De Man Rogose Sharp (MRS) medium, to simulate real conditions in the food chain. The highest antagonistic activity was observed with cell-free supernatants of exponential MRS broth cultures of the strains isolated from breast milk, followed by lactobacilli from white brined and green cheese. The detected antimicrobial activity against the pathogen was strain-specific and depended on the culture conditions. Lactobacillus (reclassified as Lactoplantibacillus) plantarum strains, cultivated in skimmed milk and whey protein medium, were able to inhibit S. Typhimurium growth, while a limited i...

Dairy Processing - From Basics to Advances [Working Title]

Production of the traditional yoghurt, white-brined cheese, and yellow cheese, named “kashkaval”,... more Production of the traditional yoghurt, white-brined cheese, and yellow cheese, named “kashkaval”, in the Bulgarian region determines everyday consumption and health benefits for the local population. Аrtisanal dairy products and their autochthonous microbiota are a promising source for the research and creation of new minimally treated, but safe, functional and delicious food. The species from Lactobacillaceae are used in different fermentation technologies, improving the structure, taste, and aroma of the final products. These products possess a prolonged shelf life due to the biopreservative capabilities of the lactic acid bacteria (LAB) strains, their positive health impact, and many physiological functions in the body. This chapter examines the traditional and modern technologies for the production of typical Bulgarian dairy products. Based on the studies of artisanal products, different LAB species from non-starter microbiota are presented, which contribute to the organoleptic ...

Journal of Fungi

Macrolepiota procera (MP) is an edible mushroom used in the treatment of diabetes, hypertension a... more Macrolepiota procera (MP) is an edible mushroom used in the treatment of diabetes, hypertension and inflammation. However, the structure and biological effects of its polysaccharides (PSs) are unclear. This study investigates the structural features of a PS complex from MP (MP-PSC), its immunomodulatory activities and effects on probiotic and pathogenic bacteria. MP-PSC was obtained by boiling water, and PSs were characterized by 2D NMR spectroscopy. The immunomodulatory effects on blood and derived neutrophils, other leukocytes, and murine macrophages were studied by flow cytometry, chemiluminescence, spectrophotometry, and ELISA. The total carbohydrate content of MP-PSC was 74.2%, with glycogen occupying 36.7%, followed by β-D-glucan, α-L-fuco-2-(1,6)-D-galactan, and β-D-glucomannan. MP-PSC (200 μg/mL) increased the number of CD14+ monocyte cells in the blood, after ex vivo incubation for 24 h. It dose-dependently (50–200 μg/mL) activated the spontaneous oxidative burst of whole b...

Iranian Journal of Veterinary Research, 2016

Probiotics and antibiotics are widely used in poultry and may alter drug bioavailability by affec... more Probiotics and antibiotics are widely used in poultry and may alter drug bioavailability by affecting the expression of intestinal ATP-binding cassette (ABC) efflux transporters. Therefore the aim of the present investigation was to evaluate the effect of Lactobacilli probiotics, administered alone or in combination with doxycycline, on the expression of ABCB1 (gene, encoding P-glycoprotein), ABCC2 (gene, encoding multidrug resistance protein 2, MRP2) and ABCG2 (gene, encoding breast cancer resistance protein) mRNAs in chicken using RT-PCR. Duc one-day-old chicks (n=24) were divided equally in four groups: untreated control, probiotics supplemented group, probiotics plus doxycycline treated chickens and antibiotic administered group. Expression of ABCC2 mRNA was affected by doxycycline or by combination of Lactobacillus plantarum, L. brevis and L. bulgaricus and the antibiotic in the intestines. These results can be used as a basis for further functional studies to prove the benefic...

Bulgarian Journal of Veterinary Medicine, 2018

Poultry feed is often supplemented by Lactobacillus probiotics which may alter drug bioavailabili... more Poultry feed is often supplemented by Lactobacillus probiotics which may alter drug bioavailability by affecting the expression of intestinal ATP-binding cassette (ABC) efflux transporters. Therefore the effect of probiotics, administered alone or in combination with enrofloxacin, on the expression of ABCB1, ABCC2 and ABCG2 mRNAs in chickens was evaluated. Day-old Ross chicks (n=24) were divided in four equal groups. Control group was not treated. The second group received feed with addition of probiotics Lactobacillus brevis, L. plantarum and L. bulgaricus 5 days after hatching, for 15 days. The third group received probiotics as described above and enrofloxacin at the age of 15 days (10 mg/kg, via drinking water for 5 days). The last group received enrofloxacin at age of 15 days (10 mg/kg, via drinking water for 5 days). Expression of ABC transporters in liver, duodenum and jejunum was determined by qRT-PCR. Down-regulation of ABCG2 mRNA in the liver (P<0.05), its up-regulation in the duodenum (P<0.05) and increased ABCB1 mRNA levels in the jejunum (P<0.05) can be attributed to enrofloxacin treatment. Decrease in ABCC2 mRNA expression in the duodenum can be associated with enrofloxacin administration. The observed changes were related to enrofloxacin administration and to lesser extent to Lactobacillus supplementation.

Trakia Journal of …, 2009

Background: Lactic acid bacteria (LAB) have become an attractive option of modern medical practic... more Background: Lactic acid bacteria (LAB) have become an attractive option of modern medical practice. Recently, attention has been paid to their health-promoting properties. Of particular importance are their probiotic properties and specially the ability to compete with pathogens in vivo. Aim: To determine the antagonistic activity of 46 LAB strains against antibiotic-resistant and other outpatient bacterial strains. Methods: Different standard protocols conform to the international rules for the data collection on antimicrobial susceptibility and on metabolic activity were applied. Results: Our hypothesis was that LAB microbiota from complex ecosystems is able to express a broad spectrum of activity. Thus, 12 vaginal lactobacilli and 34 food-originated lactobacilli, lactococci and enterococci were studied. The production of organic acids is clearly involved in antagonistic activity of these bacteria in vitro. Eight out of the tested isolates were active against Staphylococcus aureus MRSA. The inhibitory activity of two vaginal and four food-originated strains was protease-sensitive and independent of the presence of lactic acid and H 2 O 2. Conclusion: These results are encouraging and prompt further research of the active LAB strains and their possible application to overcome the problem with increasing multi-drug resistance in clinical practice.