Original Research ArticleA comparative investigation on the inhibition kinetics of bioaccumulation of As(III) and As(V) ions using Bacillus arsenicus MTCC 4380

In the context of global environmental and social change, with increasing pollution and deterioration of biodiversity of terrestrial and aquatic ecosystems having its deep roots in radical changes to hydrological mesocycles, there is an urgent requirement for a new approach for sustainability. The ecohydrology concept covers the entire hydrological cycle, including its atmospheric, terrestrial and aquatic phases, and the entire cycle of biological components of the environment playing a vital role as moderators of water quality and quantity. In the present study the simultaneous growth and bioaccumulation of As(III) and As(V) ions of living cells of Bacillus arsenicus MTCC 4380 was studied as a function of pH, inoculum size, concentrations of peptone and arsenic (As(III) or As(V)) ions. Although both As(III) and As(V) ions resulted in an inhibition effect on the growth of the bacteria, B. arsenicus MTCC 4380 was capable of removing As(III) and As(V) with the maximum bioaccumulation % of 90.43 and 94.31 at 50 mg/L initial arsenic concentration, respectively at pH 7.0 and inoculum size 5% (v/v). As the maximum specific growth rate (μm) remained constant and the saturation constant (K′S,app) value increased in the presence of increasing concentrations of arsenic ions, the inhibition of As(III) or As(V) ions on the growth rate of B. arsenicus MTCC 4380 was found to be a competitive inhibition. The current investigation provides a new insight into the effect of As(III) and As(V) ions on B. arsenicus MTCC 4380, exclusively with regard to its toxicity, bioaccumulation and bioremediation potential.