Modelling of optimum conditions for bioaccumulation of As(III) and As(V) by response surface methodology (RSM)

Abstract

The significant factors affecting the simultaneous growth and bioaccumulation of arsenic (As(III) or As(V)) ions by metal adapted living cells of bacteria, Bacillus arsenicus MTCC 4380 was explored under various pH. The optimum pH was found to be 7.0 for both As(III) and As(V) resistant B. arsenicus MTCC 4380. The combined effects of initial peptone and arsenic (As(III) or As(V)) ion concentrations on the specific growth rate and arsenic bioaccumulation efficiency of bacteria were analysed by response surface methodology (RSM). A 22 full factorial central composite design was effectively used for the experimental design and analyses of the results. Two numerical correlations fitted to a second order quadratic equation were obtained to estimate the responses of specific growth rate and arsenic (As(III) or As(V)) bioaccumulation yields. The optimum combination predicted via RSM proved that B. arsenicus MTCC 4380 was capable to bioaccumulate As(III) and As(V) up to 79.4% and 85.03%, respectively, in the growth medium containing 1000mg/L arsenic (either As(III) or As(V)) and 9g/L peptone. The present study provides a new insight into the influence of As(III) and As(V) ions on B. arsenicus MTCC 4380, exclusively relating to its toxicity, bioaccumulation and bioremediation potential.