BIOREMOVAL OF TOXIC COPPER(II) IN STRICT AEROBIC AND ANAEROBIC CONDITIONS BY TWO ENVIRONMENTALY PROMISING MICROBIAL STRAIN PSEUDOMONAS LACTIS UKR1 AND CLOSTRIDIUM BUTYRICUM GMP1
Havryliuk O, Hovorukha V, Tashyrev O, Gladka G.
D.K. Zabolotny Institute of Microbiology and Virology of the NAS of Ukraine,
Department of extremophilic microorganism’s biology
Pollution of the environment by heavy metals is constantly increasing. In the last decade, biological methods of purification of contaminated sites are gradually displacing typical physico-chemical methods. Biotechnological methods of Cu(II) removal based on the application of strains of aerobic microorganisms are widespread. Relying solely on the properties of individual strains, such methods are often ineffective. That is why it is necessary to study a new methodological approach to develop new methods of microbial treatment of copper-contaminated sites. Therefore, the aim of the study was to compare the efficiency of bioremoval of soluble Cu(II) by strains of strict aerobic and anaerobic microorganisms.
Thermodynamic prognosis method was used to substantiate the possibility of Cu(II) bioremoval by strict aerobic and anaerobic bacteria. Cultivation was conducted in Lysogeny Broth with 200 ppm Cu(II) at 30°C. Duration of cultivation was 5 and 25 days for anaerobes and aerobes respectively. Potatoes were used to cultivate the Clostridium butyricum GMP1 as an additional electron donor for fermentation. The Cu(II) concentration was determined by a colorimetric method with 4-(2-pyridylazo)resorcinol (PAR).
The thermodynamic prediction allows theoretically substantiating the most effective mechanisms of microbial removal of soluble toxic Cu(II) ions. They are the transformation to insoluble and non-toxic compounds such as Cu2O, Cu(OH)2 and the accumulation inside microbial cells. The strict anaerobic microorganisms create the lowest values of the redox potential in the medium and remove Cu(II) with maximum efficiency due to the high difference between the donor (microorganisms) and acceptor (Cu(II) compounds) systems. Thus, the efficiency of Cu(II) removal by C. butyricum GMP1 was 85% after 4 days of fermentation with 200 ppm Cu(II). In contrast to anaerobes, Cu(II) bioremoval efficiency by aerobic Pseudomonas lactis UKR1 at the same concentration was twice lower – 46% after 21 days of cultivation.
Thus, both strains were shown to be able to effectively remove toxic copper compounds from solutions. Despite the extremely toxic effects of soluble Cu(II) compounds on anaerobic bacteria (due to the strong oxidizing properties of copper), they are able to self-regulate the redox potential to optimal negative values and remove Cu(II) with greater efficiency than more studied and adapted strict aerobic bacteria. It is obvious that microbial methods are cost-profitable and environmental friendly in contrast to physical-chemical methods. The obtained results are the basis for the development of environmental biotechnologies for wastewater treatment from soluble Cu(II) compounds.