Aflatoxin B1 binding by Lactobacillus brevis isolated from brewer´s grains

GERBALDO, GISELA; ASURMENDI, PAULA; RUIZ, FRANCISCO; PASCUAL, LILIANA; DALCERO, ANA; BARBERIS, LUCILA

Mendoza

Conferencia; Mycored Argentina: ISM 2011 Conference; 2011

Universidad Nacional de Río Cuarto in the frame of EU Mycored project and co-organized by the International Society for Mycotoxicology (ISM) and The Latin American Society for Mycotoxicology (SLAM)

Aflatoxins (AFs) are a group of carcinogenic mycotoxins produced mainly by strains of Aspergillus flavus, A. parasiticus and A. nomius. Aflatoxin B1 (AFB1) is of particular interest because is associated with liver toxicity in humans and animals. Have been proposed numerous physical, chemical and biological methods to remove inactivate or reduce the bioavailability of AFB1. Lactic acid bacteria (LAB) due to their use as probiotics are of particular interest to be applied in reducing the bioavailability of AFB1. The removal of AFB1 involves physical capture of the toxin probably by the bacterial cell wall or wall components. The aim to the present work was to determine the adsorption capacity of AFB1 by L. brevis with antifungal properties. L. brevis isolated form brewer´s grains was cultivated in de MRS broth at 37°C, under a 5% CO2 atmosphere for 24 h. The bacterial cells (2-3 x 109 CFU mL-1) were enumerated using the pour-plate method. After incubation, cells were harvested by centrifugation. The bacterial pellet was washed twice with 1 mL of sterile PBS, suspended in 1 mL of PBS containing 150 ng of AFB1 and incubated at 37°C for 4 h. To determine the stability of the bacterial-AFB1 complex, this was washed three times and the amount of released AFB1 determined. The bacterial-AFB1 complex was washed by suspending in PBS (1 mL), vortexed for 15 s. and incubating at room temperature for 5 min. Then, the bacterial cells were centrifuged and the supernatant collected for quantification of released AFB1. This procedure was replicated two additional times. The effect of pH and bile salts on the reduction of AFB1 by bacterial strain was tested after incubation for 4 h at 37°C. The pH of the PBS medium containing AFB1 was adjusted to 2.0, 3.0, 4.0 and 7.0 and the PBS medium containing 0.05, 0.15, or 0.3% (w/v) of bile salts with AFB1. For each assay, a bacterial control and an AFB1 control were also incubated. The percentage of AFB1 binding by L. brevis was 73.5%. After the washes, the amount of AFB1 released by bacterial strain was only 9 %. The binding of AFB1 by bacterial strain at pH 2.0 and 0.3% of bile salts not was modified compared with the control (p