Abstract

Aflatoxin B₁ (AFB₁) can cause carcinogenic, mutagenic, teratogenic and immunosuppressive effects in humans and animals. Several lactic acid bacteria species have the ability to bind AFB₁ in vitro, showing a potential application for reducing the bioavailability of AFB₁ in contaminated products. Thus, the aim of this study was to evaluate the capacity of Lactobacillus rhamnosus, non-viable and dried, in removing the AFB₁ from a contaminated medium. L. rhamnosus were cultured in MRS broth, sterilized (121 ºC, 15 min.) to inactivate their metabolism and then dried by spray-drying or freeze-drying (lyophilization). Binding assays using AFB₁ (1.0 µg/ml) and L. rhamnosus cells (1×10¹⁰ cells, in suspension or spray-dried or freeze-dried) were conducted at pH 3.0 and 6.0, room temperature and contact time of 60 min. Quantification of AFB₁ was achieved by high performance liquid chromatography. Scanning electron microscope was also performed in order to analyze the drying effect on the atomized and lyophilized L. rhamnosus cells. For pH 3.0 and 6.0, there were no significant differences between AFB₁ binding efficiency by L. rhamnosus cells in solution (45.9 ± 8.8% and 35.8 ± 7.7%, respectively) or freeze-dried (36.6 ± 7.1% and 27.2 ± 4.0%, respectively). However, the spray-dried cells lost completely the AFB₁ binding capacity during atomization, which damaged the structural and functional properties of the bacterial cell wall. In conclusion, L. rhamnosus retained its AFB₁ binding ability only when its cell wall remained intact as observed in the lyophilization procedure. Lyophilized L. rhamnosus cells therefore can be a practicable alternative for decontamination of food products susceptible to aflatoxin contamination.

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