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.

Keywords:
S. cerevisiae; lactic acid bacteria; mycotoxins; dairy; aflatoxins