In Vitro Bioaccessibility Assessment as a Tool to Predict the Toxicity of Bioremediation Products

The demand for the development of bioremediation processes designed to maintain healthy environments has increased; however, evaluation of the toxicity of its products is needed. Therefore, the toxicity of the Cd-loaded beads of the bioremediation approach developed in this paper was evaluated by using in vitro human gastrointestinal simulation (BARGE method). Cd-loaded beads were obtained from adsorption experiments of Cd from artificial groundwater (AGW) and natural river water (NRW, Walkham River, England) using Ca-alginate beads containing live cells of the mutant Brevibacillus agri C15 CdR and its wild type B. agri C15, in batch flasks. The results showed that the Ca-alginate beads containing the mutant adsorped a significant concentration of Cd (1700 mmolal), related to its adsorption capacity. Cd-loaded beads had higher concentrations of Ca and Na (2030 ± 40 and 4300 ± 18 molal, respectively), related to its composition. The effects of the gastrointestinal simulation showed that Ca had the highest bioaccessible concentrations from Cd-loaded beads of all tested elements (Al, Ca Co, Cu, Fe, K Mg, Na, and Zn) from (1280 ± 13.00 molal); while some other elements were not detected at the end of the gastrointestinal system. Cd bioaccessibility was significantly lower in the Cd-loaded beads containing the mutant (0.17 and 0.14 molal in the gastric and gastrointestinal phases, respectively), compared to the wild type (0.23 and 0.19 molal, respectively). The bioaccessible fractions (BAFs) of Cd were significantly lower in the Cd-loaded beads containing the mutant at the gastric and gastrointestinal phase, with the mean of 4.85 % and 2.95 %, respectively. The low percentages of BAFs of Cd suggested that the products of the bioremediation process developed in this project might not be relevant as a human health risk.