The Ability of Lactobacillus rhamnosus in Solution, Spray-Dried or Lyophilized to Bind Aflatoxin B1

Abstract

<p>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<em>in vitro</em>, 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 <em>Lactobacillus rhamnosus</em>, non-viable and dried, in removing the AFB₁ from a contaminated medium. <em>L. rhamnosus</em> 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 <em>L. rhamnosus</em> 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 <em>L. rhamnosus</em> cells. For pH 3.0 and 6.0, there were no significant differences between AFB₁ binding efficiency by <em>L. rhamnosus</em> 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, <em>L. rhamnosus</em> retained its AFB₁ binding ability only when its cell wall remained intact as observed in the lyophilization procedure. Lyophilized <em>L. rhamnosus</em> cells therefore can be a practicable alternative for decontamination of food products susceptible to aflatoxin contamination.</p>