Head: Assoc. prof. Ekaterina Krumova, PhD
Tel.: +359 2 979 31 26
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Head: Assoc. prof. Ekaterina Krumova, PhD
Tel.: +359 2 979 31 26



Assoc. Prof. Radoslav Abrashev, PhD
Tel.: +359 2 979 31 28




Main scientific field

Research within the Group is focused on filamentous fungi, isolated from various sources (including samples from extreme environments) at different levels: molecular, cellular, whole organism and biocenotic.

Main Research Topics

  • Taxonomic identification of fungal species;
  • Fungal morphology, physiology and biochemistry under normophysiological and stress conditions;
  • Fungal cell response against different type of stresses such as oxidative stress, heat- and cold shock, stress of immobilization and heavy metal exposure; evaluation of oxidative stress biomarkers; antioxidant enzyme defense;
  • Fungal cell factories for production of valuable biological-active compounds by free and immobilized cultures; cold-active enzymes; regulatory mechanisms in the biosynthesis; purification and characterization of enzymes;
  • Fungal biodegradation of natural and synthetic polymers (wood, leather, textile, historical records, etc.); laboratory expertise, consultations, instructions for preservation and elimination of fungi; mechanism of action of fungicide substances; methods for application of fungicides.


  1. Fungal diversity

 A sizeable fungal collection was developed along with the isolation of strains from temperate and extreme environments. The collections contains strains from Alaska, different regions of Antarctica, Bulgarian caves and tombs, as well as fungal inhabitants in Egypts tombs and mosques.  There are species from the three major groups of true fungi: Basidiomycota, Ascomycota and Zygomycota. Most of them were identified to genus and species level. According to the temperature range for growth, they were classified as extremely psychrophilic, psychrotolerant or mesophilic fungi. Lignolityc fungi are new addition in the collection. The investigations provide new information on the mycelial biodiversity in these habitats as well as their biotechnological potential.

  1. Oxidative stress (OS)

 We focus our attention on better understanding OS response in lower multicellular eukaryotes. Filamentous fungi from different species are using as model microorganisms. Treatment of the fungal strains with various stimuli generating reactive oxygen species (ROS) induces a state of oxidative stress. Related research targets evaluation of: (1) stress biomarkers (cyanide-resistant respiration; direct assessment of ROS production; oxidative damaged proteins; synthesis of reserve carbohydrates etc); (2) antioxidant enzyme defense (superoxide dismutase, SOD and catalase, CAT); (3) subcellular localization of SOD isoenzymes; (4) changes in activities of key enzymes from basic metabolite pathways. In addition, we are studying the relationship between oxidative stress and cell aging.

  1. Relationship between OS and other types of stresses
  •  Metal-induced stress. Our results provide additional evidences for OS mediating copper toxicity in filamentous fungi. Biomarker response to the heavy metal was quite equal with treatment involving a more direct application of ROS, such as paraquat. Adaptive response to heavy metal treatment refers to the ability of cells to better resist the damaging effects of the toxic agent when first preexposed to a lower dose.
  • Heat-shock. Another particular area of interest concerns the hypothesis of a common signal for heat shock (HS) and OS. Evidence is provided for the possibility that the OS plays a major role in the effect of enhanced temperature in Aspergillus niger. The treatment resulted in increase in cyanide-resistant respiration, ROS generation, corresponding accumulation of the reserve carbohydrates (trehalose and glycogen), increase in protein carbonyl content, and activation of antioxidant enzyme defense. This knowledge may be of importance in controlling both fermentation and pathogenicity.
  • Metabolite adaptation to cold temperatures. Antarctica and the life of filamentous fungi in the extreme environment are also an interest of our research group. Our investigations confirm that the effect of temperature down shift on cell response of Antarctic fungi are comparing with this in European temperate strains. It has been found that a sharp decrease in temperature resulted in changes in morphology, physiology and metabolism of the model strains, allowing them to survive in extreme conditions. Synthesis of temperature-sensitive enzymes has been demonstrated. Compared to temperate mesophilic strains, Antarctic fungi (psychrophilicand mesophilic) demonstrated adaptations, which permit survival in low-temperature conditions.
  • Stress of immobilization. Our results clearly demonstrated that immobilization influences the physiological behavior of fungal cells. Immobilized niger cells showed significant increase in activities of key enzymes of the glycolytic pathway, pentose shunt, and tricarboxylic acid cycle compared to the free cell culture. Moreover, immobilization elicits the enhanced synthesis of antioxidant enzymes that demonstrate an association between state of immobilization and oxidative stress.
  1. Fungi as cell factories for production of valuable biological-active compounds
  •  Original fungal strains producers of biological-active compounds were isolated and characterized. The group has a high qualification in the development of laboratory methods for the production of extra- and intra-cellular
  • High effective technology for biosynthesis of naturally glycosylated Cu/Zn-SOD by the fungal strain Humicola lutea 103 (HLSOD) was elaborated. The novel enzyme exerts a far higher pharmacological activity than non-glycosylated enzymes. HLSOD was fully characterized and used in in vivo models for the demonstration of its protective effect against myeloid Graffi tumor in hamsters and influenza virus infection. Furthermore, the antioxidant enzyme improves fertility of ram and bull spermatozoa during liquid storage and cryoconservation.
  • A new direction in our work are physiological and biochemical investigations of the biosynthesis and regulation of activity of valuable cold-active enzymes in psychrophilic and psychrotrophic fungi, using existing collections of Antarctic strains. Effective technology for biosynthesis and purification of cold active Cu/Zn-SOD from the Antarctic fungal strain Aspergillus glaucus has been developed. A fermentation strategy based on the effect of cold stress was used to improve the enzyme yield. A high purified enzyme preparation was obtained. Such specific activity (4000 U/mg) is comparable or even higher than the activity of commercial mesophilic Cu/Zn-SOD. The molecular mass of the major enzyme (15 835 Da) was determined by ESI-Q-TOF mass spectrometry and DLS. The presence of Cu and Zn were confirmed by inductively coupled plasma mass spectrometry (ICP-MS). The N-terminal amino acid sequence revealed a high degree of structural homology with Cu/Zn-SOD from other fungi.
  1. Fungal biodegradation of natural and synthetic polymers

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.




Granted by National Funds

  • Catalase in antarctic fungi: antioxidant role, localization, regulation and properties (DN-01/1), 2016-2019, The National Science Fund of Ministry of Education and Science
  • New ecotechnologies for biodegradation of organic waste with production of hydrogen and methane (DFNI-E02/13 with assoc. prof. Ivan Simeonov) The National Science Fund of Ministry of Education and Sciences
  • Investigation of fungal biodiversity in Magura cave duration 2017, Funding organization Ministry of culture
  • Proteome analysis of new natural peptides with antibacterial and antifungal activity, isolated from snail Cornu aspersum(DN-01/14), 2016-2019, The National Science Fund of Ministry of Education and Science
  • Role of amarylic alkaloids in endophyte-host relationships, (ДН01/13 with prof. Strahil Berkov), 2016-2019, Funding organization - The National Science Fund of Ministry of Education and Science
  • Innovative approach for biological treatment of lignocellulosic wastes for biogas production, 301 / 02.18.2016, Program for support  of  young scientists in BAS, 2016

Bilateral projects

  • Biotechnological production of cold-active enzymes by fungi

(D-r . Tosi, University of Pavia, Italy), 2013-2015

  • Fungi as source of lignolytic enzymes. Production and possible applications. (D-r . Savino, University of Pavia, Italy), 2015-2018

 EBR  projects

  • Study of the physiological, biochemical and ecological characteristics of micromycetes resistant to heavy metal stress

Project leader: M. Angelova, DSc Project collaborator: V. Grishko, PhD, Ukrainian Academy of Sciences,         Botanical Garden

  • Efficacy of antimicrobial substances produced by streptomyces in modifying polymers used in conservation of paintings in some ancient egyptian tombs

Project leader: M. Angelova, DSc Project collaborator: M. Farrag, PhD, Zagazig University, Faculty of Science, Botany Department, Egypt  



  • Kostadinova, N., Tosi, S., Spassova, B., Angelova, M. Comparison of the oxidative stress response of two antarctic fungi to different growth temperatures. Polish Polar Research, Vol. 3, 2017 (in press)
  • Miteva-Staleva, J., Krumova, E., Vassilev, S., Angelova, M. Cold-stress response during stationary growth phase of Antarctic and temperate Penicillium Microbiology UK, 2017 (in press)
  • Krumova, E., Kostadinova, N., Abrashev, R., Miteva-Staleva, J., Spassova, B., Angelova, M. Antarctic fungal strategies for overcoming cold stress. Microbiology for a better health and industry, 2017, ISBN:978-954-92882-2-3
  • Abrashev, , Feller, G., Kostadinova, N., Krumova, E., Alexieva, Z., Gerginova, M., Spasova, B., Miteva-Staleva, J., Vassilev, S., Angelova, M. Production, purification and characterization of a novel cold -active superoxide dismutase from the antarctic fungus Aspergillus glaucus. Fungal Biology. 120, 2016, 679-689.
  • Krumova, E., Kostadinova, N., Miteva-Staleva, J., Grishko, V., Angelova, M. Cellular response to Cu- and Zn-induced oxidative stress in Aspergillus fumigatus isolated from polluted soils in Bulgaria, CLEAN, Soil Air Water, 44, 2016, 657-666.
  • Savino, E., Girometta, C., Miteva-Staleva, J., Kostadinova, A., Krumova, Wood Decay Macrofungi: Strain Collection and Studies about Antioxidant Properties. Compt. rend. Acad. bulg. Sci., 69, 6, 2016, 747-755.
  • Abrashev, , Krumova, E., Kostadinova, N., Miteva-Staleva, J., Spasova, B., Angelova, M. Improvement of superoxide dismutase production by heat shock treatment of Aspergillus niger 26. Compt. rend. Acad. bulg. Sci., 68, 11, 2015, 1379-1386.
  • Abrashev, R., Stoitsova, S., Krumova, E., Pashova, S., Paunova-Krasteva, T., Vassilev, S., Dolashka-Angelova, P., Angelova, M. Temperature-stress tolerance of the fungal strain Aspergillus niger 26: physiological and ultrastructural changes. World Journal of Microbiology and Biotechnol 4, 30, 5, 2013,1661-1668.
  • Krumova E., Abrashev R., Miteva-Staleva J., Pashova S., Angelova M. Regulation of superoxide dismutase synthesis in Humicola lutea cells under Cu2+ stress conditions. Comptes rendus de l’Acad´emie bulgare des Sciences, Ren. 'Acad. Bulg. Sc., 66, 2013, 525-532.
  • Krumova E., Stoitsova S., Paunova-Krasteva T., Pashova S., Angelova M. Copper stress and filamentous fungus Humicola lutea 103 — ultrastructural changes and activities of key metabolic enzymes. Can. J. Microbiol., 2012, 58(12), 1335-1343
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