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

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.