Copper(II) Bioremoval by a Rhizosphere Bacterium, Stenotrophomonas acidaminiphila MYS1-Process Optimization by RSM Using Box–Behnken Design

Abstract

A copper-tolerant bacterium strain MYS1 was isolated from Brass effluent-contaminated Cynodon dactylon rhizosphere and identified as Stenotrophomonas acidaminipila by 16S rRNA analysis. Bacterium culture was enriched in copper(II) supplemented nutrient broth. Bacterial potential for copper(II) bioremoval was investigated under optimized parameters. Three parameters—pH, temperature and copper(II) concentration—were optimized through response surface methodology (RSM). Box–Behnken design (BBD) with quadratic model was selected. Seventeen experimental runs were carried out to get the desired response. Model’s significance was confirmed by high R2 value (0.9941), low P value (<0.0001) and F value (131.32). Effect of different parameters on bioremoval of copper(II) was determined by response contour and surface graphs. Results showed that optimum values for copper(II) removal were obtained at pH (5.0), temperature (32.5 °C) and copper(II) concentration (250 mg/L). Under these optimized conditions, maximum bacterium growth (2.87 µg/mg) and copper(II) bioremoval (94.1%) were demonstrated after 120 and 168 h of incubation, respectively. High percentage of copper(II) removal at such a higher concentration confirmed the feasibility of bacterium Stenotrophomonas acidaminiphila MYS1 in copper bioremediation and industrial effluent treatment.