FEMS Journals Poster Prize: Lili Ivaylova Dobreva

FEMS Online Conference on Microbiology 2020
Lili Ivaylova Dobreva and Prof. Svetla Danova

We send our congratulations to Lili Ivaylova Dobreva, who won the Poster Prize at the FEMS Online Conference on Microbiology 2020, sponsored by the FEMS journals.

The FEMS Online Conference on Microbiology took place between the 28th and 31st of October 2020 as a virtual conference. Her winning poster was titled “Characterisation of lactic acid microbiota of Bulgarian traditional product “katak””.

Read our interview with Lili about her research below:


What is your current position and what was your scientific journey to get there?

I am a PhD student (last year) in “The Stephan Angeloff” Institute of Microbiology, Bulgarian Academy of Science.  Since January, 2020 I am also Assistant prof. in Department of General Microbiology, laboratory of “Microbial Genetics –Lactic acid bacteria & Probiotics“. I graduated my Bachelor degree in Biology at Ryerson University, Canada followed by Msc degree of Biobusiness – at Sofia University “St. Kliment Ohridski, Faculty of Biology in 2016, with a thesis – „Business plan for the production of an innovative probiotic soft drink based on water kefir“. Thus, a theoretical knowledge in food microbiology, obtained in the University, encouraged me for further development in the field of modern microbiology and biotechnology. The scientific challenge – from tradition to new fermented functional food and probiotics motivated my doctoral thesis: “Functional characteristics of lactic acid bacteria isolated from different habitats.” I was happy to become a part of one Laboratory with several years research on Lactic acid bacteria & Probiotics, with supervisor prof. Svetla Danova, DsC. The research projects of our group are devoted to lactic acid bacteria (LAB) in different aspects, from isolation identification, taxonomy to their characterization as probiotics. The beginning with katak’s microbiota characterization was done by PhD thesis of Dr. Tropcheva R. (2013) and Dr. Nemska V.(2017). The aim of my PhD thesis is to continue with characterizаtion of LAB strains from not-well studied habitats and researching their mode of beneficial effects to propose the form in which they can be realized as new functional food or formulas for preventions and /or therapeutic health condition approaches. The long-term goal is to study the probiotic mechanisms of LAB  (lactic acid bacteria) adequately for health and to be able to apply them for improvement of the quality of life of, as in recent years, the links between nutrition, the state of the intestinal microbiome and health have been proven.  My main areas of research interests include microbial genetics and food microbiology; functional food, lactic acid bacteria and probiotics, mode of beneficial action.”


Could you describe the research your poster covered?

The aim of our study was to investigate and characterise lactic acid microbiota of Bulgarian traditional product -“katak”. Katak is famous and well-known traditional Bulgarian dairy food, a naturally fermented lactic- acid product with a pleasant taste, part of Bulgarian non-material cultural heritage. It is unique not only because of its taste but also with its long shelf-life for up to 1 year without preservatives. The product attracted our attention because of its abundant lactic acid microflora and high microbial number for the whole storage period. We started with 22 pure cultures identification, according to modern polyphasic taxonomy, combining classical microbiological and molecular methods. With the help of species-specific PCR, species belonging to L. brevis, L. rhamnosus, L. fermentum  were characterized, and with multiplex PCR  we identified the facultative heterofermentative family of the group L. plantarum, which have recently been assigned to the the new genus Lactiplantibacillus plantarum. Predominance of heteroforementative lactobacilli is observed, and the species affiliations of some of the isolates have to be precised, as they are clustered closest to some of the taxons in the new genus Lactiplantibacillus.

Most interesting, however, is the broad spectrum of antagonistic activity, not only against Gram-positive (Staphyloccocus aureus ) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa),but also activity against food pathogens, that present serious problem in the food chain, such as  Salmonella enterica, which is responsible for half of Salmonellosis  infections.  In vitro promising results could be a base for further research and application.

In cooperation with colleagues from Department of Mycology we also gathered evidence of good antifungal activity against carcinogenic and toxigenic fungi. In different of variants of agar- diffusion method, we have achieved complete inhibition of Fusarium graminearum, Aspergillus flavus, Aspergillus niger, Trichoderma viride and others.

Probably the Lactobacillus strains can naturally protect us from undesirable pathogenic microorganisms. In order to exploit their bio-protective role, they must be alive, under forms appropriate for human administration. Therefore, we design a model system to estimate LAB’s transit tolerance through a passage of the gastrointestinal tract. Some of the strains showed very good survival in conditions such as low pH 2, 3, 4. Therefore they could be appropriate food/probiotic adjuncts.

Katak’s LAB strains also possess a unique enzymatic activity, estimated by Api-zym system  ( BioMerieux, France) A predomination of LAB strains with beta-galactosidase activity is observed, which could help ease the problem with increasing lactose intolerance. Other enzymes are α-glucosidases and hydrolases for the sugar metabolism, may allow combining them as promising starter’s adjuncts. This metabolic activity can lead to a series of active metabolites, some of which are characterized -lactic acid, carbon dioxide, diacetyl.

This study presently is a part of an active research project, with financial support of National scientific found (KP 06 OPR03/16) grant. My scientific interest unifies well with the research projects of the Laboratory of Microbial genetics of LAB & Probiotic. However, I have to learn a lot, because science moves rapidly in order to answer the needs of society. Therefore, our long term-goal programme is to characterize the beneficial properties of the microflora of traditional dairy products; which we believe are a rich source of future probiotics and to transfer them to new technology, according to the new consumers’ demands for minimally treated but safe and healthy food. Thank you for your attention, we would be happy to expand our partnership with other laboratories and to work together to preserve unique tradition on the Balkans in dairy functional foods, consumed from centuries.”


What do you hope to focus your research on in the future?

I am really happy to be a part from microbiological team working on the characterization of beneficial microbes. I am challenged from the possibilities of new Omics technology in characterization of probiotics. I would like to expand my research on further characterization the molecular basis of beneficial properties of lactic acid bacteria and evaluation of their probiotic potential and safety. The most important, however is how to combine functional and technological properties for the purpose of developing new functional foods with benefits for the human microbiome and health.

I am interested in functional foods in alternatives (non-dairy) environments for the inclusion of probiotics, such as their inclusion in plant yogurt-like products, combining the specifics of the substrate with selected Bulgarian strains of lactic acid bacteria with certain health benefits. Rapidly growing lactose intolerance, allergies to casein and other milk proteins deprive larger groups of the population of the opportunity to consume dairy products and non-dairy alternative. Due to the growing vegan population, non-dairy alternatives are gaining popularity as suitable substrates for feeding and including probiotics and it would be beneficial if these groups have healthy dairy alternatives.”

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