Use of scanning electron microscopy and high-performance liquid chromatography to assess the ability of microorganisms to bind aflatoxin M-1 in Minas Frescal cheese

The aim of this study was to evaluate the capacity of two strains of lactic acid bacteria (LAB), Lactobacillus rhamnosus and Lactococcus lactis, and a yeast strain, Saccharomyces cerevisiae, inactivated by heat (121 degrees C, 10 min), from binding to aflatoxin M-1 (AFM(1)), as well as the interaction between these microorganisms, aflatoxin M, and the Minas Frescal cheese matrix after 2 and 30 days of storage. The ability of LABs and S. cerevisiae to bind AFM(1) to Minas Frescal cheese was evaluated by high performance liquid chromatography (HPLC) composed of a fluorescence detector. The interaction between these microorganisms and AFM(1) was evaluated using a scanning electron microscope composed of a backscattered electron detector with a voltage of 15 kV and magnifications of 1000 x, 5000 x and 8000 x. The use of microorganisms as a biological method is efficient in reducing AFM(1) in Minas Frescal cheese and does not affect the microbiological parameters. AFM(1) reduction varied according to the microorganism used in the treatments. S cerevisiae showed greater capacity to bind AFM(1) over time, compared to LABS. Scanning electron microscopy was especially useful, confirming that lactic acid bacteria and S. cerevisae were able to bind AFM(1) particles in Minas Frescal cheese.