Effect of Metal Cations on Selenite Bioreduction by a Consortium of Halophilic/Halotolerant Bacteria and/or Yeast

Selenium oxyanion pollution in the environment, often originating from anthropogenic industrial activities, causes significant risks to human health and the ecosystem. The selenite bioreduction to the less toxic form of selenium, Se (0), by microbial species and consortia offers a promising approach for bioremediation of polluted environments. This study explores the effects of potentially toxic co-contaminating metal cations, including cadmium (Cd), lead (Pb), and zinc (Zn), on the bioreduction of selenite by a consortium of halotolerant and halophilic bacteria and yeast. The effectiveness of the consortium in reducing selenite was investigated in conditions that mimic multi-metal pollution found in the real world, with varying levels of the different metals. The results showed that Pb and Cd had negative effects on the mixed consortium efficacy, while Zn showed an augmenting effect on the bacterial consortia. Also, molybdate significantly reduced selenite removal in all consortia. Kinetic analyses using the Michaelis-Menten model were applied for evaluating the rate of selenite reduction. Also, selenium biosorption and dispersion in microbial cells were studied using electron microscopy and EDS analysis. The findings provide insights into the use of microbial consortia in contaminated environments and highlight the potential for bioremediation strategies that can cope with multiple pollutants.