Ability of Lactobacillus rhamnosus GAF01 to remove AFM1 in vitro and to counteract AFM1 immunotoxicity in vivo

Aflatoxin M-1 (AFM(1)) has been detected in many parts of the world both in raw milk and many dairy products, causing great economic losses and human disease. Unfortunately, there are few studies dealing with AFM(1) immunotoxicity/interactions with lactic acid bacteria for potential application as a natural preventive agent. The aim of this study was to isolate (from dairy products) food-grade probiotic bacteria able to degrade/bind AFM(1) in vitro and evaluate whether the same organism(s) could impart a protective role against AFM(1)-induced immunotoxicity in exposed Balb/c mice. Bacteria (Lactobacillus plantarum MON03 and L. rhamnosus GAF01) were isolated from Tunisian artisanal butter and then tested for abilities to eliminate AFM1 from phosphate-buffered saline (PBS) and reconstituted milk (containing 0.05, 0.10, and 0.20 mu g AFM(1)/ml) after 0, 6, and 24 h at 37 degrees C. Results showed that the selected bacteria could 'remove' AFM1 both in PBS and skimmed milk. The binding abilities of AFM(1) by L. plantarum MON03 and L. rhamnosus GAF01 strains (at 10(8) CFU/ml) in PBS and reconstituted milk ranged, respectively, from 16.1-78.6% and 15.3-95.1%; overall, L. rhamnosus showed a better potential for removal than L. plantarum. 'Removal' appeared to be by simple binding; the bacteria/AFM(1) complex was stable and only a very small proportion of mycotoxin was released back into the solution. L. rhamnosus GAF01 had the highest binding capacity and was selected for use in the in vivo study. Those results indicated that use of the organism prevented AFM(1)-induced effects on total white and red blood cells, and lymphocyte subtypes, after 15 days of host treatment. These studies clearly indicated that L. rhamnosus GAF01 was able to bind AFM 1 in vitro and-by mechanisms that might also be related to a binding effect-counteract AFM(1)-induced immunotoxicity. Moreover, by itself, this bacterium was not toxic and could potentially be used as an additive in dairy products and in biotechnology for mycotoxin detoxification.