Microorganisms and Bioremediation

In Central Asia, there are several storage sites for radioactive waste, which can be called environmental “hot spots” due to their negative impact on the environment, public health and the high risk of destruction of storage facilities during possible natural and technogenic disasters. Such “hot spots” of particular concern include Mailuu-Suu, Min-Kush and Kazhi-Sai in Kyrgyzstan, Charkesar in Uzbekistan, Taboshar and Degmay in Tajikistan. In such ecologically unfavorable zones, toxic elements (radionuclides and other heavy metals) exceed the maximum permissible concentration by tens and hundreds of times [1].

Prospects for improving the environmental situation in these cities and towns are possible only if a set of measures is taken, including the rehabilitation of contaminated areas, reclamation of dumps and tailings using more accessible, proven and environmentally friendly methods.

It is known that cleaning the environment from xenobiotics from the 27 types of treatment technologies developed 6 are based on methods using microorganisms [2].

All biotechnological processes are based on microbiological processes, and the main “face” and instrument that ensures the passage of certain reactions are microorganisms - a very important branch of the living world. Indeed, thanks to microorganisms, the first photosynthetic microorganisms arose, which ensured the formation of an oxygen atmosphere on Earth and the development of higher plants. But the most important role of microorganisms today is biodestruction and biooxidation. Everything that is produced on earth by living beings - microorganisms, plants, animals and humans, is ultimately utilized by microorganisms that is, decomposed into simple substances: carbon dioxide, molecular nitrogen, salts of other elements. Thus, microorganisms are the cleaners of the planet, which ensure the constant functioning of our biosphere.

The bioremediation method is recognized as one of the effective methods of cleaning the environment from anthropogenic pollution. Bioremediation - set of soil and water purification methods based on the use of the biochemical or metabolic potential of microorganisms (bacteria, fungi), algae, and higher plants.The undoubted advantages of this method are efficiency, cost-effectiveness, environmental safety and the absence of secondary pollution [3,4]. Bioremediation using microorganisms has received much attention due to their good efficiency and use in converting toxic heavy metals into a less harmful form [5].

Long-term field and laboratory studies have revealed the toxicity of radioactive elements and heavy metals on a complex of soil microorganisms, which has made it possible to create collections of new strains of bacteria, actinomycetes and microscopic fungi that are especially resistant to increased concentrations of heavy metals, radionuclides and petroleum products that are promising for the production of biological products for cleaning contaminated environments.

Selected strains of microorganisms were isolated from various types of natural and contaminated soil ecosystems of Kyrgyzstan in the areas of uranium tailings dumps and their adjacent territories: in the areas of the village Min-Kush, Kazhy-Sai, Ak-Tyuz, Orlovka and cities of Kara-Balta and Mailuu-Suu.

We are conducting research on the selection of strong, effective strains of microorganisms capable of accumulating and transforming high concentrations of heavy metals, in order to use them in the future for the development of environmental bioremediation technology.

Previously [6], we showed that among the selected strains in the complex, 2 strains of bacteria of the genus Bacillus in associations showed noticeable resistance to high concentrations of Hg up to 0.75 mg/l in liquid and 1 * 10-1% in 100 ml agar media and Pb at concentrations up to 1.5-2 mg/l; Cd at concentrations up to 1.5 – 3 mg/l.

As a result of the studies, it was shown that the bacterial strains used (H-5-8 Bacillus megaterium + H-5-2 Bacillus cereus) can accumulate fairly high concentrations of lead up to 5 mg/l in the environment. However, the optimal concentrations are up to 1 mg/l, where the specific growth rate and biomass of crops have maximum values, and mercury up to 0.75 mg/l in the environment.

In addition, the proposed strain H-5-2 Bacillus cereus has not only the accumulative properties of heavy metals, but also has high antagonistic activity against phytopathogenic fungi that cause root rot. Thus, biological products based on the association of strains of soil spore-forming bacteria can be used for the purpose of bioremediation of soils contaminated with heavy metals, while at the same time protecting plants in contaminated zones from phytopathogenic microorganisms.

The selected strains are stored in the laboratory collection under numbers H-5-8 (Bacillus megaterium) and H-5-2 (Bacillus cereus) and a patent was obtained (Patent No. 815 KR) in the use of these strains for cleaning soils and aquatic environments from pollution heavy metals. Thus, the development of technology for bioremediation of soil contaminated with any chemical substance is a long, multi-stage process that requires the collaboration of specialists in various fields: microbiologists, analytical chemists, biochemists, biotechnologists and toxicologists. This work, despite its duration and versatility, ultimately makes it possible to develop effective, environmentally friendly and low-cost technologies for soil bioremediation.

1. Djenbaev BM, Kaldybaev BK, Zholboldiev BT. Problems of uranium waste and radioecology in mountainous Kyrgyzstan conditions radioactive. Waste Rehab Abdel Rahman. IntechOpen. 2012. doi: 10.5772/33618.
2. Vel'kov VV. Bioremediation; principles, problems, approaches. J Biotechnology.1995;3(4):20-27.
3. Alexander M. Biodegradation and bioremediation. Academic Press, New York; 1999.
4. Feruke-Bello YM, Babalola G, Olu O. A comparative study of the wild and mutated heavy metal resistant Klebsiella variicola generated for cadmium bioremediation. J Bioremediation. 2018;22(1-2):28-42. doi:10.1080/10889868.2018.1445695.
5. Akcil A, Erust C, Ozdemiroglu S, Fonti V, Beolchini F. A review of approaches and techniques used in aquatic contaminated sediments: metal removal and stabilization by chemical and biotechnological processes. J of Cleaner Production. 2015;86:24-36. doi: 0.1016/j.jclepro.2014.08.009.
6. Omurgazieva Ch.M, Konurbaeva MU. Bioremediation potential of soil bacteria of heavy metal polluted environments of Kyrgyzstan /Microbial communities and their interactions in the extreme environment. Part of the Microorganisms for Sustabiability. Springer, Singapore. 2021;32:315-341. 2021. doi: 10.1007/978-981-16-3731-5.