Applications of Lactobacillus bulgaricus (lactic acid bacteria) as dispersive solid phase sorbent for sample preparation of heavy metals from aqueous samples

• The use of the renewable, biodegradable Lactobacillus bulgaricus (LAB) biomass as an effective biosorbent for the extraction of Cd(II), Ni(II), and Zn (II) . • The use of LAB in dispersive solid phase extraction (DSPE) procedure is solvent-free, low-energy, and operationally simple, aligning with green sample preparation methods. • Effective performance in real wastewater samples confirms the method's practical relevance and supports its integration into environmentally responsible monitoring systems. The use of bacteria as biosorbents for the extraction of trace metals from aquatic environments offers a cost-effective and durable approach for sample preparation in the analysis of trace metals. Due to its large surface area, divers’ functional group and the high affinity for metal ions, bacterial biomass is considered as an ecofriendly sorbent to separate and preconcentrate trace metals from complex matrices, which allows their analysis precisely. Compared to traditional sorbents, renewable biosorbents require significantly less energy to produce. Thus, their application supports the valorization of organic waste and aligns with sustainability principles. This study evaluates the feasibility of using Lactobacillus bulgaricus, a lactic acid bacterium (LAB), to extract and preconcentrate cadmium (Cd), nickel (Ni), and zinc (Zn) from aqueous solutions. The LAB species was isolated from bacterium cultivated in an anaerobic medium and then exploited in dried form as biosorbent for the extraction of metals using a dispersive solid phase extraction (DSPE) approach. The impact of key parameters on biosorption process including pH, contact time, adsorbent dosage, and the initial concentration of the metal ions in solution on biosorption process were systematically examined. Freundlich, Langmuir, Redlich-Peterson, Dubinin-Radushkevich, and Temkin isotherm models are used to analyze and interpret the results of batch biosorption experiments, providing insights into the adsorption behavior and mechanisms. Zn(II) Ni(II), and Cd(II) ions had adsorption capacities of 92, 105, and 120 mg/g onto LAB biomass at pH 6, respectively. The inter-particle diffusion, Elovich, and the pseudo-second order (PSO) models are used to analyze the adsorption kinetics. These results reveal the substantial potential of LAB biosorbent as a sustainable and effective sorbent for sample preparation (purification/preconcentration) of trace metals prior to their detection. Furthermore, this bacterium may perhaps be a feasible substitute for managing water contamination in wastewater treatment systems.