Use of scanning electron microscopy and high-performance liquid chromatography to assess the ability of microorganisms to bind aflatoxin M1 in Minas Frescal cheese

Abstract

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 °C, 10 min), from binding to aflatoxin M1 (AFM1), as well as the interaction between these microorganisms, aflatoxin M1 and the Minas Frescal cheese matrix after 2 and 30 days of storage. The ability of LABs and S. cerevisiae to bind AFM1 to Minas Frescal cheese was evaluated by high performance liquid chromatography (HPLC) composed of a fluorescence detector. The interaction between these microorganisms and AFM1 was evaluated using a scanning electron microscope composed of a backscattered electron detector with a voltage of 15 kV and magnifications of 1000 ×, 5000 × and 8000 ×. The use of microorganisms as a biological method is efficient in reducing AFM1 in Minas Frescal cheese and does not affect the microbiological parameters. AFM1 reduction varied according to the microorganism used in the treatments. S cerevisiae showed greater capacity to bind AFM1 over time, compared to LABs. Scanning electron microscopy was especially useful, confirming that lactic acid bacteria and S. cerevisae were able to bind AFM1 particles in Minas Frescal cheese.