Study On Co-culture Of Two Acidophilic Uranium-leaching Bacteria And Characteristics Of Extracellular Polymeric Substances

With the increasing demand of global nuclear energy development for uranium resources,the industrial application and promotion of uranium bio metallurgy technology have attracted much attention.It is the key to reveal the interaction mechanism between uranium leaching microorganisms and minerals in Bio-leaching Technology.In this paper,two Acidithiobacillus ferrooxidans(At.f)F1-f and UBK35 were isolated from different uranium mine environments,and one acidocella was isolated and purified from uranium acid heap leaching solution The main factors affecting the pure culture and mixed culture of the three strains were studied,and the optimal ratio of mixed culture was determined.Based on this,the effects of extra-cellular polymeric substances on the pure culture and mixed culture of the three strains were further studied The production characteristics of substance(EPS)lay a foundation for the further study of uranium leaching mechanism in pitchblende by these three mixed bacteria.The main achievements of this study are as follows:(1)the optimum culture conditions of strain B3-19WJX were:culture temperature25°C,inoculation amount 5%,pH value 3;.The optimum growth temperature of F strain F1-f and UBK35 was 30°C,under the condition of 20%inoculation and 120 rpm,5 g/L Fe²⁺was oxidized in 24 h.Acidithiobacillus ferrooxidans F1-f,UBK35 and strain B3-19WJX were mixed culture,the optimal combination ratio was 2:9:9 when the inoculation amount was 20%.(2)the maximum concentration of exopolysaccharide of each strain was in the stable growth period,and the concentration of exopolysaccharide increased obviously under mixed culture,the maximum concentration was close to 50?g/mL,which appeared in the late logarithmic growth period of the mixed strain.The secretion of exopolysaccharides was positively correlated with the growth activity of bacteria.The maximum concentration of extra-cellular protein of autotrophic strain UBK35 was at the beginning of stable period,and the maximum concentration of extra-cellular protein of mixed culture was 45.7?g/mL,at the beginning of the logarithmic period.The secretion of extra-cellular proteins is related to the environment and the mechanism of protein expression,but not to the metabolism of bacteria.(3)the main functional groups of EPS are-OH,-COOH and-NH₂,which correspond to the presence of polysaccharide and protein in EPS.These functional groups have an important influence on the structure and physicochemical properties of Bio-leaching bacteria,and also play an important role in Bio-leaching minerals.