Removal of cadmium and lead from doogh and mineral water by Lactobacillus acidophilus and Bacillus coagulans

This study examined the effectiveness of Lactobacillus acidophilus and Bacillus coagulans in removing heavy metals (lead and cadmium) from doogh (a fermented yogurt drink) and mineral water. Both live and heat-inactivated forms of these bacteria were added to the beverages containing lead and cadmium, and stored at 4 °C. The concentrations of the heavy metals were measured at intervals of 1, 2, 7, 15, and 35 days using ICP-OES. FTIR and SEM analyses were conducted to investigate the functional groups and accumulation processes, respectively. Additionally, sensory evaluations were performed on samples without heavy metals by panelists. The results showed that all probiotic bacteria could remove lead and cadmium from the samples, although their adsorption rates varied. On the first day of storage, the residual concentrations of lead and cadmium ranged from 0.06 ± 0.01 to 27.62 ± 0.06 mg/L and 23.19 ± 0.07 to 51.62 ± 0.21 mg/L, respectively. Bacillus coagulans in mineral water (pH: 6.59) demonstrated the highest removal efficiency (p < 0.05). FTIR results indicated that functional groups such as amides, carboxylic acids, and hydroxyl groups were involved in binding to lead and cadmium ions. SEM analysis revealed changes in the surface morphology of bacterial cell walls in the presence of metal ions, indicating absorption. Sensory analysis showed that all matrices containing bacteria had higher scores, which decreased over 35 days of storage. The study concluded that the effectiveness and mechanisms of bacterial strains in removing heavy metals depend on the type of matrix, the presence of competing ions, pH, and the condition of the bacterial biomass (dead or alive). The findings suggest that probiotic bacteria, particularly Bacillus coagulans, can effectively remove heavy metals from beverages without significantly affecting their sensory properties.