Academician Tsvetan Tsvetkov has turned 60 years old

Human life judged not so much by the number of years, as by what one has done to the benefit of the public and society. This is especially true of people who have dedicated their entire lives to science.
In these terms the life of academician Tsvetkov has been filled with meaning and deeds to the objective of research advance into a specific area – cryobiology and lyophilization. Along these lines the lifetime activity of acad. Tsvetkov has been deeply meaningful, consistent and publicly motivated.
He was born on 12 September 1943 in a family that has preserved the Bulgarian national revival spirit and ideals of the revolutionary region of Chiprovtsi and Berkovitsa. In 1968 he graduated with honours from the Technological University in St. Petersburgh. He received a Master of Technical Sciences for the brilliant scientific work included in his diploma paper and was offered a full-time post-graduate position to study at the same university. What followed were days and years of hard research to mastering the theoretical basis of a subject interrelated with large number of human activities – food technologies, medicine, space travel, dietology, etc.
In 1971 Tsvetkov defended successfully his thesis and got the title of Doctor of Technical Science. He was appointed as research scientist at the Refrigeration Technology Institute in Sofia. There he established (1973) and became head of the first Bulgarian Cryobiology and Lyophilization Laboratory. Quickly Tsvetkov managed to turn it into a modern laboratory for both consistent research into, and production of various bio-products with various applications. Years of laborious activity were dedicated to expanding the score of the laboratories research as well as creating connections with similar specialized laboratories and institutes abroad.
In 1973 Tsvetan Tsvetkov became Senior Research Associate, 2nd degree. Then, in 1979, following the successful defense of his Doctor of Science thesis he attained the rank of Senior Research Associate, 1st degree. In the same year he was appointed part-time professor at the Higher Institute of Food Industry in Plovdiv. Since 1987, Tsvetkov has been full-time professor at the same institute.
Based on a proposal made by the Presidium of the Agricultural Academy in 1989 the Bulgarian government transformed the problem-oriented laboratory, headed by Prof. Tsvetkov, into the Cryobiology and Lyophilization Institute. This was a high recognition not only of the scientific activity of Tsvetkov, but also of his excellent organizational talent and his ability to generate ideas for theoretical research as well as for creation of new scientific products. Hard work and extensive research had preceded these milestones of success. Prof. Tsvetkov was excellent at broadening the research areas of his team, and managed to integrate them with the worldwide network of specialized scientific centers. The Cryobiology and Lyophilization Institute commenced joint research work with the specialized laboratory of the US Red Cross organization, the International Cryogenics Institute in Paris, the US Association of Tissue Banks, the International Confederation of Thermal Analysis and Calorimetry, the Japanese Society of Low-temperature Medicine, and a number of scientific centers in the former USSR. For the organization of such a wide-range cooperation the unique credit goes to Prof. Tsvetkov. For this reason he was chosen as a member in all these organizations. A high international appreciation of this activity was his being elected Vice President of the Cryobiology and Lyophilization Commission at the International Cryogenics Institute in Paris. Since 1977 Prof. Tsvetkov has represented Bulgaria in the Cryobiology and Lyophilization International Association based in the USA. This is yet another recognition of the scientific and organizational activity of acad. Tsvetkov, for his significant contributions in the field of cryobiology and lyophilization.
The considerable role of acad. Tsvetkov in establishing the cooperation between our Cryobiology and Lyophilization Institute and acknowledged international scientific centers is evident in the estimate made by Prof. Dr. Harold Merriman, Program Director of the US Naval Medicine Research Institute in Washington: "The cooperation set up by Prof. Tsvetkov has provided opportunities for exchange of extremely useful information on the mechanism of low-temperature tolerance in plants, as well as on issues concerning oxygen exchange through transfused red blood cells and hemoglobin. We highly esteem the research contributions of Prof. Tsvetkov, and his experience in the production of bone and skin preparations for clinical application, used by the US Association of Tissue Banks.”
This high appreciation on behalf of the great experts in the field of cryobiology and lyophilization is a proof of acad. Tsvetkov`s incontestable achievements at the institute he runs, both in the theoretical investigations and the production of biopreparations.
In 1989 Prof. Tsvetkov was elected correspondent-member, and in 1995 a full member (academician) at the Bulgarian Academy of Science (BAS). These acts of high recognition were preceded by years of hard, dedicated work in a particularly difficult research field.
The scientific research of acad. Tsvetkov has been done in the field of cryobiology and lyophilization, more precisely in fundamental cryobiology. His major findings have been documented in over 250 papers and studies. About 140 of them have been published in foreign scientific journals and publications of international organizations. One of the most highly credited US journals, Cryobiology, has published 35 of his works. This scientific production includes 11 monographs, 1 of which written in German and 2 – in Russian, 14 monographic books, a number of text books, reference books, reviews and leaflets.
A considerable part of acad. Tsvetkov`s findings have been dedicated to theoretical and methodological issues, concerned with the substantiation of different hypotheses for applied science developments in the field of cryoconservation and lyophilization. For example he provided original theoretical grounds for the hypothesis of the cold hardiness of animals and plants and the attending cryodamages and cryoprotection under low-temperature conditions. On this basis innovative parameter regimes were invented and also technologies for sublimation and cryogenic treatment and preservation of tissue organs, various types of cells, tissues, viruses and bacteria.
Another original theoretical contribution made by acad. Tsvetkov is his mathematical model of heat and mass transfer in the process of sublimation drying of biomaterials. On this basis an equation was developed to define the process intensity. Optimization was achieved for a method for foodstuff heating in the process of sublimation drying. Of particular value are acad. Tsvetkov`s studies on optimizing the coefficient for determining the heat physical and mass transfer traits of foodstuffs and various biomaterials. The utilization of these coefficients has led to development of original methods and technological methodology. Also, special equipment has been created for designing of vacuum sublimation installations for the food industry. A comprehensive concept has been worked out and ways have been demonstrated for process intensification, optimization, and improvement of machines and equipment used in cryobiology and lyophilization, with the aim of manufacturing automated production lines for the needs of food industry. These machines have been object of interest on behalf of foreign specialized companies and organizations.
A particular part of the researches led by acad. Tsvetkov has been oriented at the development of foods and rations for the needs of astronauts and other groups of people working under extreme conditions. The good theoretical understanding of the diets and needs of this group of people has allowed for the creation of a wide range of foodstuffs of original composition. These developments have made Bulgaria the third country in the world that has sent foodstuffs in space. The quality of these foodstuffs has been ranked high by cosmonauts and astronauts participating in the astronautics congress held in Sofia. These foodstuffs have remained unsurpassed in their quality.
Under the guidance of acad. Tsvetkov and with his personal participation the Cryobiology and Lyophilization Institute developed a scientific branch of cryoconservation of tissue cultures, organs and organelles. Unique achievements have been made in this direction concerning the methods and methodology of their conservation and their quality parameters as well. This estimate has been confirmed by transplantations that have been performed for more than two decades now at home and abroad. Moreover, this applies not only to medical products but also to all the developed bioproducts and biopreparations. A number of countries have shown interest in lyophilized foods not only for special purposes but for mass consumption, too. A lot of specific factors determine the high quality of the bioproducts. In this respect of special importance are the original cryogenic technologies with preprogrammed technological action upon each individual product according to its structural peculiarities, rheology and chemical composition. All this ensures maximum level of preservation of their nutritive value and biological sufficiency.
The outstanding talent of acad. Tsvetkov, to generate ideas and organize cooperation with scientist from other biological branches in national an foreign research centers, has been the basis for the fast expansion of the institute's research, and the attaining of the high results mentioned above.
A new area of interest in the institute headed by acad. Tsvetkov is the development of methods for long-term preservation of genetic material of breeding forms, valuable mutants, plant or tree species threatened with extinction, and unique cell strains. The methods evolved under his guidance have permitted an enlargement of the scope and specter of the forms preserved in the available genetic blanks with an extended lifetime for their preservation. Along the same lines are the developments of acad. Tsvetkov for long-term thermal conservation of animal isolated mitochondria, conservation of red blood cells, specific-term conservation of human monocytes, and conservation of kidneys intended for transplantation. In this aspect a number of universally valid principles have been found, which have allowed for development of effective cryoconservation technologies.
Thanks to the research of acad. Tsvetkov and the activity of the institute he has been in charge of, Bulgaria has taken one of the leading position in the utilization of cryoconservation and lyophilization methods. In this sphere acad. Tsvetkov has founded a Bulgarian school and prepared specialists for expanding this field. He is also the founder and the head of the International Cryobiology and Lyophilization School. This School holds biennial workshops and has been approved as an international scientific and training forum.
The activity of acad. Tsvetkov as the establisher and leader of the International School can be assessed by the high appreciation offered by Dr. Arthur Roe, editor-in-chief of the Cryobiology journal and manager of the Medical Center at the University of Lemsig (New York): "In 1983 Prof. Tsvetkov set up International Cryobiology and Lyophilization School thus creating a faculty of internationally renowned scientist. I have had the privilege to work at this faculty as a lecturer and attendee. I hold in high esteem his role for the preparation of young scientist and post-graduate students."
The scientific and training activity of acad. Tsvetkov has been ranked high by Prof. David Pegg, manager of Cryobiology Department at the Applied Biology Institute at the York University in the town of York, UK: "The research papers of Prof. Tsvetkov have earned high scientific acknowledgement and contributed greatly to the progress made in the field of general biology.”
Acad. Tsvetkov has rendered great services to the development of knowledge in the field of cryoconservation and sublimation drying. He is equally credited for dissemination of the knowledge and methods in this field. The 11 monographs he has published are valuable methodological manuals both for research, and for the high level production of bioproducts.
Of special interest in this respect is the monograph "Scientific grounds of the sublimation preservation technology”, published in Russian. It dwells on the theoretical basis that enabled the formation of technological processes for low-temperature and sublimation preservation of bioproducts of various types. An analysis is presented of the parameters used and the nature of the individual stages in freezing and sublimation drying. Definitions are provided of the rates of freezing, the nature of cryoprotectors, the conditions and regime of drying. A comparison has been made between the theoretical calculations and the experimental data for the separate types of products. A successful attempt has been made to determinate the common principles that allow the management of the technological process in cryogenic and sublimation conservation. Therefore, the monograph is a particularly useful methods handbook both for researchers and experts, as well as designers of cryogenic equipment.
In the field of medicine, acad. Tsvetkov`s monographs on the subjects of cryobiology and blood are of particular value as methodology papers, tissue transplants, blood biopreparations, and bioproducts for medical practice. Rundowns of these methodology manuals have been published in a large number of specialized publications. Apart from the theoretical conclusions and the experimental material discussed in them, they offer precious operation methods in the related production activity.
Since 2000 acad. Tsvetkov became an Editor-in-Chief of Bulgarian Journal of Agricultural Science.
A considerable part of acad. Tsvetkov`s technologies and methods for efficient bioproducts for food, medical, and special purposes have been patented. Their originality and high effectiveness have attracted the interest of specialized companies and firms from abroad. On these grounds projects have been evolved for joint ventures.
Acad. Tsvetkov has been a long-term lecturer at the University of Food and Beverage Industry in Plovdiv. His rich specialized knowledge and teaching talents are at the core of the affection on behalf of students, graduates, and post-graduates. His activity as director of studies has resulted in the successful defending of 25 PhD theses and 25 graduation papers. He has also been in charge of specialization courses of a great number of specialists from home and abroad.
The fruitful academic teaching activity of acad. Tsvetkov has been recognized by the University awarding him the title of Doctor Honoris Causa.
Acad. Tsvetkov has actively participated in the international research areas. He is member of many international scientific organizations and centers. He has delivered more than 86 papers at international scientific congresses and symposia, 62 of which held at foreign scientific centers.
Since 2000 acad. Tsvetkov has been the President of the National Center for Agrarian Sciences. This has been an unusually difficult period for the national agricultural scientific system. The difficulties arising from the transitional period of the economy have been aggravated by the evident desires for privatization of a large number of experimental bases. To this we have to add the destructive behavior of "reformatory-scientists" trying to release themselves from inferiority complexes on the wave of the ongoing processes and changes in the country as a whole. Under these circumstances the responsibility and the weight lying on the shoulders of the President of the Agricultural Scientific System have been particularly heavy.
Bulgaria needs of well-developed agricultural science. This is one of the prerequisites for overcoming the crisis that our agricultural production has been into. This is also one of the key terms, for Bulgaria to preserve the production of specific products, in the process of joining the EU.
We are confident that acad. Tsvetkov has the strength to defend the interests of the national agricultural scientific system. Let us wish him health, fortitude and courage to surmount the hardships. Not only the agricultural, but the entire Bulgarian scientific community have been following with concern the efforts for preserving the agricultural scientific potential, and the available research and experimental base. We believe that acad. Tsvetkov has the power to fulfil his civic duties.

Acad. Tseno Hinkovski
Bulgarian Journal of Agricultural Science