Removal of cadmium, lead, and chromium by Lactobacillus helveticus KD-3: Influential factors, adsorption mechanism, and application in goat milk powder

The Lactobacillus helveticus KD-3 strain that could remove cadmium (Cd), lead (Pb), and chromium (Cr) was selected to explore the effect of temperature (4–40 °C), bacterial concentration (2.0–10.0 g/L), adsorption time (0.1–6.0 h), and pH (2.0–8.0) on the removal rates of these heavy metals. The adsorption mechanism of single and mixed heavy metals was revealed through SEM-EDS, FTIR, and XPS. When the adsorption temperature was 40 °C, the maximum removal rate of Cd was 29.08 %. At pH 6.0 and 4.0, the maximum removal rates of Pb and Cr were 83.37 % and 49.16 %, respectively. The cell surface showed obvious wrinkles after absorption, suggesting that Cd, Pb, and Cr were toxic to KD-3. The main biosorption mechanism was the binding of heavy metals to functional groups (N–H, O–H, C–H, COO⁻, and C–O–C). XPS analysis confirmed the reduction of Cr(Ⅵ) to Cr(Ⅲ) after adsorption. In addition, goat milk powder containing 4.3 × 10⁸ CFU/g of KD-3 was prepared and demonstrated the ability to remove coexisting Cd and Pb in vitro effectively. This study emphasizes the significance of adsorption conditions, provides insights into the adsorption mechanism, and further exhibits the potential for L. helveticus KD-3 to adsorb mixed heavy metals in the food industry.