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DEPARTMENT OFMORPHOLOGY OF MICROORGANISMS AND ELECTRON
MICROSCOPY
 The ultracytochemical localization of acid phosphatase in nongerminating and germinating
conidia of the fungus Humicola lutea is established for the first time. The distribution in the
mycelia is clarified.
 Original evidence is obtained about the fine structural changes of model Gram-positive and
Gram-negative bacteria under the action of rhamnolipid-biosurfactant with surface-active
properties.
 The ultrastructural peculiarities, the growth and reproductive capacity of producers of
thermostable exo-inulinase and cyclodextrin glucanotransferase immobilized on different
matrices (polysulphone membranes, agar gel) are characterized.
 A correlation is determined between the ultracytochemical localization of succinate
dehydrogenase of some bacteria and the changes in the lipoproteid content of their
membranes under the action of Lubrol W.
 Original cytochemical evidence is collected for the cell-surface and intracellular distribution
of polysaccharides with defined lectin-binding capacity in some Gram-negative and Grampositive bacteria.
DEPARTMENT OF MICROBIAL BIOCHEMISTRY
 For the first time it is found that the Pomorie mud is an inductor of enzyme neuraminidase
secretion at pathogenic genera Vibrio and Aeromonas because of the presence of sialic acids
in the mud.
 From different microbial strains were isolated, identified and characterized biosurfactants
with effective surface and emulsifying properties and were found promising for application
in biomedicine, bioremediation and biotechnology.
 Microbial transformation of the steroid compounds sitosterol and androstenedione was
performed by resting cells of Mycobacterium sp. and Rhodococcus sp., respectively, in a
single phase organic solvent based medium.
 A modified chemostat technique called titrostat was developed for selective isolation and
continiuous flow cultivation of rapidly growing bacteria utilizing toluene vapours as a single
source of carbon and energy.
 A simple and rapid test for differentiation of aerobic from anaerobic bacteria was developed
applicable for determination of the respiratory type of pure cultures isolated from different
areas of the environment.
DEPARTMENT OF MICROBIAL GENETICS
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The physiological and biochemical peculiarities of the original yeast strain Trichosporon
cutaneum R57, which is highly active in degrading many aromatic and aliphatic compounds
– toxic pollutants of the environment were investigated. The biochemical analysis of the
first three enzymes of the catabolic pathway of degrading phenol in carbonless media
enhanced the elucidating of their key role in the process. A system for homologous and
heterologous protoplast fusion and protoplast transformation of Trichosporon cutaneum
R57 strain was elaborated. A specific oligoneucleotide probe was applied for the
identification of microbial strains with the potential of degrading toxic aromatic
compounds, isolated from polluted soils and waters. Dot-blot hybridization analysis for the
identification of catabolic genes, coding enzymes with phenol-hydroxilase activity was
carried out.
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Original approaches to the molecular-taxonomic characterization of lactic acid producing
bacteria and the rapid monitoring of Lactobacilli from different ecological niches were
developed.
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The genetic, physiological and other factors, controlling the sexual process of the yeast
Hansenula polymorpha were investigated. Two special types of homothalism were
uncovered: a copulation potential in all possible combinations and sporulation of haploid
strains.
DEPARTMENT OF MICROBIAL BIOSYNTHESIS AND BIOTECHNOLOGY
 A method for production of extra cellular α-galactosidase was developed by submerged
cultivation of Aspergillus niger M47 , Penicillium chrisogenum LN33 and Humicula lutea
1205 on the medium, composed by wastes from food industry. The method was submitted
for patent (Patent Application№ 109202/23.06.2005 Aleksieva, P., Nacheva, L.,
Tchorbanov, B., Bratovanova, E. Method for obtaining of α-galactosidase (by free
cells);PatentApplication№ 109929/02.08.2007Institute of Microbiology, Institute of
Organic Chemistry, Aleksieva, P., Nacheva, L., Tchorbanov, B., Bratovanova, E.,
Yakimova, B. Method for obtaining of α-galactosidase (by immobilized cells).
 A Lab biotechnology for galanthamine production by Leucojum aestivum shoot culture was
developed. This is the first bioreactor process reported for production of Galanthamine by in
vitro plant system.
 A detailed “know-how” for production of L-lysine and a Lab biotechnology for production
of L-valine were developed.
 From culture medium of a thermophilic strain two indole alkaloids (microbiareton and
microbiaeratinin) were isolated and their cytotoxic and antialgic activities were established.
 An alkaline hydrolysate from animal wastes was obtained and their influence on chemical
and microbiological properties of the poor soils were investigated. The obtained results
outlined the possibilities for its application as an organic fertilizer.
 The growth of methylotrophic yeasts Hansenula and Pichia on glucose, methanol and
glycerol as carbon source was investigated. The presence of catalase and superoxide
dismutase (SOD) activity in fractions of mitochondria, cytosol and peroxisomes were
investigated. It was established that peroxisomal catalase was located in the mitochondrial
matrix and SOD( besides the typical places for localization- mitochondria and cytosol)was
detected in peroxisomes as well.
 The proteolytic system of starter lactobacteria was characterized and it was established that
this system is a criterion for their participation in starters for milk products.
 In situ baceriocins production of LB. bulgaricus BB18 and LB. lactis BCM5 was studied
and their strain compatibility with two technological strains S. thermophilus 11A and Lb.
bulgaricus LX1 was demonstrated for forming starters for fermented milks with health
benefits.
 The strain Streptomyces sp., producer of antibiotic complex, was identified by
hemotaxonomic and genetic methods as Streptomyces iakurus DSM 41873. The antibiotic
complex is composed of 5 new components, which were characterized by their molecular
masses and chemical structures.
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 The colloid properties of glucomannan, synthesized by psychrophilic stain were studied.
The comparison of the cream emulsions with glucomannan and those with emulsifiers
rofetan and arlacel ( used in cosmetic industry) showed that they were with equal stability.
 The yeast strain, producer of phytase was isolated from Antarctic samples. The appropriate
culture medium and parameters of cultivation were established for high production of
phytase. The enzyme kinetics and properties were determined as well.
 By flow cytometry the genom sizes of the cells of Beta vulgaris intact plants and hairy root
cultures were determined. It was established that in contrast to the primary plant tissues, the
obtained hairy roots are mixoploids., due to several cycles of endoreduplication. Such
difference currently is not reported in the available scientific literature.
DEPARTMENT OF MICROBIAL ECOLOGY
 Original baker's yeast strains - Saccharomyces cerevisiae were selected. These strains have
high trehalose content and high maltase activity.
 Method for quantitative determination of biotin applying specially selected methanol
utilizing yeast strain was elaborated.
 Strains of Aspergillus niger producers citric and gluconic acids under double limitation of
nitrogen and phosphorous during their cultivation were selected.
 The mathematical model of growth and production of citric acid on different carbon sources
was developed.
 The strains bioindicators and detectors of heavy metal and pesticides pollution were
selected.
 Microbial association degrading phenol was selected
DEPARTMENT OF MYCOLOGY
 A sizeable fungal collection was developed along with the isolation of strains from
temperate and extreme environments, including Antarctica.
 New evidences were given for the relationship between oxidative stress and various
environmental challenges (heavy metals, heat- or cold-shock, cell immobilization).
Evaluation of specific oxidative stress biomarkers (generation of reactive oxygen species,
cyanide resistant respiration, oxidative damaged proteins, storage carbohydrates) and
enzyme antioxidant defense were carried out.
 Unusual existence of Cu/Zn-SOD in mitochondrial intermembrane space (IMS) was
evidenced. This is the first identified naturally glycosylated enzyme, isolated from IMS.
 High effective technology for biosynthesis of naturally glycosylated Cu/Zn-SOD by the
fungal strain Humicola lutea 103 was elaborated. The novel enzyme was fully
characterized and used in in vivo animal models for the demonstration of its protective
effect against Graffi tumor and influenza virus infection. This enzyme improves fertility
of ram and bull spermatozoa during liquid storage and cryoconservation.
 New information about biotechnological potential of Antarctic fungi was obtained.
 Due to the current knowledge about morphology and biochemistry of the filamentous fungi,
as well as the professional experience some methods concerning the preservation of
natural polymers from fungal biodegradation were developed.
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DEPARTMENT OF EXTREMOPHILIC BACTERIA
 A moderate thermophilic bacterial strain Bacillus sp. UG-5B with benzonitrilase activity
was isolated from polluted industrial waters. The benzonitrile degradation was realized via
nitrilase pathway. Due to the high enzyme thermostability of free or immobilized cells as
well as the broad substrate specificity, the isolated strain, Bacillus sp. UG-5B could have a
potential application in chemical synthesis or various detoxification processes.
 An effective synthesis of cyclodextrin glucanotransferase was realized by magnetic
biocatalysts containing cells of Bacillus circulans ATCC 21783 and enzyme with a high
specific activity was obtained.
 A new isolated bacterial strain representing novel species, Anoxybacillus rupiensis, was
isolated from Bulgarian hot spring.
 The originally isolated from Bulgarian hot spring Bacillus stearothermophilus strain was
described as the only producer of thermostable gellan lyase reported up to now. Its
thermostability determines the possibility for running industrial processes at temperature
higher than 60°C in which temperature gellan is soluble.
DEPARTMENT OF PATHOGENIC BACTERIA
 Bacterial-host interactions (invasion, persistence, intracellular survival, as well as the
bioenergetic mechanisms ensuring these processes) were characterized. Pathogenesis of
experimental melioidosis, listeriosis, yersiniosis, salmonelosis, etc. and immune response of
different hosts were established in details.
 Yersinia outer membrane proteins have been isolated and used in improved ELISA and
immunoblot tests for routine laboratory diagnosis of natural yersiniosis in humans and pigs
and experimental yersiniosis of rabbits.
 Aiming development of new generation of live carrier vaccines, clinical, immunological and
pathomorphological examinations were carried out after experimental oral infections of
rabbits with two wild and four genetically constructed mutantс of Yersinia enterocolitica
O:8. A lower virulence and bacterial load of viscera, weaker morphological changes, better
immunogenicity and well expressed tissue tropism to the lymphoid tissue of the mutant
strains wzzGB and sodA-314 in comparison with mutants 8081-R2, wbcEGB and wild
strains WA-314 and 8081-L2 were established.
 The role of Yersinia LPS antigen in induction of reactive arthritis was proved in
experimental mouse and rat models.
 The incidence and transmission of multidrug-resistant Mycobacterium tuberculosis strains
in Bulgaria were examined by using advanced molecular epidemiological methods and
population structure analysis. The multidrug resistant and hypervirulent Beijin strain was
not found in Bulgaria. The results contribute to control the global spread of multidrug
tuberculosis worldwide.
 The photoinhibitory effect could be used in the practice for photosterilization of
contaminated with enterobacteria water ecosystems.
 The method of PCR-DGGE was optimized and successfully applied for direct detection and
typing of Campylobacter jejuni and C. coli in caecal samples of broilers without preliminary
enrichment. This method allows reliable and fast detection and identification of pathogenic
Campylobacters being causative agent No.1 of food-born infections in humans.
DEPARTMENT OF VIROLOGY
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DEPARTMENT OF IMMUNOLOGY
 The ability of the opportunistic yeast Candida albicans to induce reactive arthritis in normal
and in predisposed individuals has been studied. The relationship between infections and
rheumatic diseases has been analyzed in detail with the aim of developing new therapeutic
approaches in rheumatic diseases.
 The immunomodulatory properties of coumarin, 7-hydroxycoumarin, yeast superoxide
dismutase and molluscan hemocyanins have been described. They have therapeutic
potential as antitumor agents as well as for the prophylaxis of infectious diseases.
 Preparing of an educational program for life-long learning in the fields of medical
microbiology and immunology for nurses, laboratory technicians, etc. has been created with
the participation of scientists from four European countries (Leonardo da Vinci Programme
of EC).
 Discovery of previously unknown mechanisms of the immunomodulatory activity of pooled
IgG (IVIg) in autoimmune patients.
 Development of experimental improved “next-generation” pooled human immunoglobulin
preparation with an improved therapeutic effect in systemic inflammatory diseases.
 Describing of the immunomodulatory potential of normal pooled human IgM in
autoimmune and inflammatory diseases.
 Development of a novel approach for silencing selectively autoreactive disease-associated B
cells in autoimmune diseases.
 Describing of the phenomenon of inflammation-induced enhancement of IgG antigen
binding polyreactivity.
 Development of DNA vaccines with a new type of build-in adjuvanticity.
RESEARCH GROUP FOR MATHEMATICAL MODELING AND COMPUTER
SCIENCES
 Models (deterministic and neural) of the anaerobic digestion of organic wastes (specific and
in mixtures) and of the production of the enzyme superoxide dismutase
 Optimisation and control algorithms for the anaerobic digestion of organic wastes (specific
and in mixtures), accompanied by biogas yield, as well as for the production of the enzyme
superoxide dismutase
 Laboratory biogas technologies based on the anaerobic digestion of organic wastes (specific
and in mixtures)
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