Selective Enrichment of Gram-positive Bacteria from Apple Juice by Magnetic Fe3O4 Nanoparticles Modified with Phytic Acid

The emergence of magnetic nanotechnology has prompted the development of novel sample preparation techniques. Phytic acid (PA) is an organophosphate compound of natural origin. Not only is it highly attractive to multivalent metal ions such as calcium, zinc, and iron, but it is also capable of forming complexes with molecules such as proteins. Here, we describe a highly cost-effective method of phytic acid-modified Fe 3 O 4 (Fe 3 O 4 -PA) for the rapid concentration and isolation of foodborne pathogens. Using three examples for Gram-negative and Gram-positive bacteria, respectively, we demonstrate the excellent selective ability of Fe 3 O 4 -PA towards Gram-positive bacteria with more than 98.76% capture efficiency for MRSA. The Fe 3 O 4 -PA trap almost completely captured Staphylococcus aureus at a concentration of about 5.82 × 10 3  CFU/mL in apple juice. Scanning electron microscopy and confocal laser microscopy experiments showed that Fe 3 O 4 -PA can be non-destructive and non-lethal for the enrichment of Gram-positive bacteria. We believe that our work provides a fast and promising method for concentrating bacteria directly from food.