Mitigation of aflatoxin M1 in milk by the magnetized Fe3O4 lactic acid bacteria cells: a response surface methodology (RSM) study

The current work aimed to optimise aflatoxin M1 (AFM1) removal from milk by magnetic inactivated lactic acid bacteria (LAB) adsorbent using response surface methodology (RSM). In this research, the ability of 5 strains of LAB was evaluated for AFM1 removal. Lactobacillus rhamnosus, which indicated the highest adsorption efficiency compared to other strains (p < 0.05), was selected. The obtained LAB was modified using Fe3O4 particles for the generation of magnetic inactivated LAB adsorbent, which was further characterised by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and vibrating sample magnetometer. The results indicated that L. rhamnosus cells were successfully functionalised and modified by Fe3O4 particles. A central composite design (CCD) was applied to investigate the effect of variables including time (5-125 min), temperature (3-23 degrees C), initial AFM1 concentration (0.1-2.1 mu g L-1), and fat (0-3.6%) on AFM1 removal from milk using synthesised adsorbent. According to the RSM model, the optimal adsorption conditions for the second-order model were observed at 73.60 min, the temperature of 17.82 degrees C, AFM1 concentration of 1.598 mu g L-1, and fat content of 0.9% leading to the maximum removal efficiency of 56.92%. Hence, the magnetic inactivated LAB adsorbent synthesised using this approach can be an efficient easy-to-separate adsorbent in removing AFM1 from milk. The main functional groups involved in AFM1 removal were carboxyl, amide, and hydroxyl/amino groups. Moreover, the synthesised adsorbent had superparamagnetic behaviour and could be rapidly separated from aqueous solutions. In conclusion, the current study presented a novel method for the efficient adsorption of AFM1 to improve the safety figures of milk.