BACTERIAL OXIDATION OF FERROUS IONS IN SUSPENDED CELLS CULTURES AND BIOFILM OF ACIDITHIOBACILLUS FERROOXIDANS JCM 3863 IN PRESENCE OF COPPER IONS
KRISTINA LAZAROVA*, VYARA MAMATARKOVA
Sofia University “St. Kliment Ohridski”, Faculty of Biology, Department of Biotechnology,8 Dragan Tsankov Blvd., 1164 Sofia, Bulgaria
*Corresponding author: kristina.r.lazarova@gmail.com
Keywords: Acidithiobacillus ferrooxidans, biofilm, copper ions
Abstract: Bacteria Acidithiobacillus ferrooxidans are usually implemented in many biotechnological processes as bioleaching of metals from low grade ores, purification of waste waters and gases, removal of metals from solid wastes etc. The bioprocess systems with biofilm of Аcidithiobacillus ferrooxidans are capable to oxidize ferrous to ferric ions in higher concentrations. The aim of this work is to investigate bacterial oxidation in suspended cultures and biofilm of Аcidithiobacillus ferrooxidans JCM 3863 in presence of copper ions and different initial concentration of ferrous ions. Submerged cultures and biofilm have been cultivated in shake flasks at 200 rpm in two media – with 9 and 12 g/l initial concentration of ferrous ions. Biofilm and submerged cultures have been cultivated in five consecutive cycles in each nutrient medium in the presence of 5 g/l copper ions to complete oxidation of ferrous to ferric ions. In the end the biofilm thickness has been determined. Mean rates of oxidation were compared for each cycle of cultivation. In consecutive cultivation of suspended cells in media 9K after the second cycle the mean rates decrease significantly. In biofilm in media 9K is observed that the mean rates are constant and even increase in the last cycle. In consecutive cultivation of suspended cells in media 12K in the last two cycles almost the rate from the first cycle is reached after decrease in the medium cycles. In biofilm in media 12K there is a gradual increase of mean rates compared to the first cycle. In summary, the biofilm is more suitable for industrial biotechnological processes in the presence of copper ions and high concentrations of ferrous ions.