Arsenic bioremediation in mining wastewater by controllable genetically modified bacteria with biochar

Abstract

Arsenic (As) is a highly toxic chemical element associated with cardiovascular diseases and diabetes. Using genetically modified microorganisms (GMOs) for arsenic detoxification or removal is taking center stage in recent years. However, the bio-safety issue of GMOs remains an obstacle. In this study, we proposed a bioremediation process to efficiently adsorb arsenic from mining wastewater by combining a controllable GMO with biochar. One metagenomic gene element (ArsR) with high arsenic adsorption efficiency was newly identified from mining wastewater environment. Then the gene was chromosomally integrated into strain Pseudomonas putida KT2440, which is a widely used strain for environmental bioremediation. The growth-regulation genetic circuit coordinating suicide gene expression was deployed onto the genome of strain KT2440. This non-auxotrophic, antibiotic-free and self-controlled programmable circuit was fine-tuned with highly sensitive perceptibility towards arsenic levels below wastewater discharge standard (< 0.50 mg/L), which made the system applicable. A biochar-microorganism coupled recovery strategy was further implemented in mining wastewater treatment, leading to increased arsenic removal capacities, which is ready for use under a circumstance up to 20 mg/L of total arsenic pollution. No more than 1.32 × 10−9 escapee of GMOs was observed in the process, which meets the US NIH guidelines for GMOs release (<10−8). Thus, this study demonstrated the feasibility for arsenic bioremediation by GMOs in industrial wastewater.