Screening of copper resistant microorganisms in mines and mathematical modeling of bioaccumulation and extracellular nanoparticle biosynthesis by Bacillus cereus

Abstract

Some microorganisms were isolated from copper mines and recognized as copper resistant. Genotyping was conducted using 16srDNA sequencing. The bioaccumulation and extracellular nanoparticle biosynthesis were conducted for Bacillus cereus under the varying copper concentration range using mathematical modeling. AFM, TEM, and particle size analyzer were used for the characterization and the nanoparticle analyses. Cell toxicity was assayed against human cells. Maximum biosorption capacities were 1200 or 2500 μg g−1 when 0.5 or 1 mg ml−1 CuSO4 was provided for the bacillus cells, respectively. In contrast, extracellular bioreduction kinetics revealed a threefold change from ≈250 to 700 μg ml−1 in the same treatment conditions. No time shift was recorded for reaching the maximum extra/intra nano-copper synthesis in both copper concentration models. Bacillus cereus synthesized nano-coppers within a range of 80–150 nm. Metal nanoparticles were at least twofold less toxic than their copper sulfate on the human cells and T47D was the most resistant cell against nano-coppers. The toxicity effects were dose-dependent, time-dependent, and also organism- and heavy metal type-dependent. The results revealed that the copper-resistant Bacillus cereus is a robust and high-throughput microorganism for intracellular and extracellular nano-copper biosynthesis.