Influence of glucose on the co-culture of Acidithiobacillus ferrooxidans and Acidiphilium acidophilum

Abstract:

[Objective] To gain a better understanding of the synergic interactions between chemoautotrophic bacteria Acidithiobacillus ferrooxidans and heterotrophic bacteria Acidiphilium acidophilum that usually occurred in bioleaching system and acid mine drainage (AMD). For suggestion on AMD bio-remediation and research foundation on ecology functions of acidophilic heterotrophic bacteria in bioleaching system and AMD environment. [Methods] The biomass dynamics of At. ferrooxidans and its natural co-culture with Aph. acidophilum in 9K-ferrous iron media with or without glucose were measured respectively by quantitative real-time PCR; meanwhile, the pH and Fe2+ oxidation were monitored. [Results] Whether the glucose was added in culture media or not, the Fe2+ oxidation efficiency of At. ferrooxidans is higher in co-culture than that in pure culture. When the concentration of glucose is 5 g/L, pure culture of At. ferrooxidans couldn’t oxidize Fe2+ while the co-culture could finish the Fe2+ oxidation in 100 h, and the pH is higher when more glucose was added in both cultures. Without glucose, the cell number ratio of At. ferrooxidans to Aph. acidophilum in co-culture was about 100:1, which suggested the usual cell number ratio between autotrophic bacteria and heterotrophic bacteria in AMD environment. Both in pure and co-culture, the cell number of At. ferrooxidans decreased and the lag phase prolonged with the increase of glucose concentration; while in the case of Aph. acidophilum in co-culture, the cell number and lag phase showed a reverse trend. [Conclusion] For efficient Fe2+ oxidiation, the proper cell number of At. ferrooxidans should be 100 times higher than that of Aph. acidophilum. Because Aph. acidophilum facilitated the Fe2+ oxidation by At. ferrooxidans and reduced the inhibition by glucose, the addition of organic compounds such as glucose could not be a good AMD bio-remediation strategy.