Abstract
Mycotoxins are naturally toxic compounds. They are considered an international health security concern. Cereals are the foodstuffs most frequently contaminated by mycotoxins. In Tunisia, wheat is the most cultivated cereal; it constitutes, with its derivatives, the backbone of the Tunisian food system. The aim of the present study is to study the occurrence of mycotoxins in the wheat sector in Tunisia by a multi-mycotoxin analysis using UHPLC-MS/MS. 136 wheat samples are collected from two different climatic regions: Kairouan and Beja. Collection is carried out at different points in the sector: in the field, at harvest, at pre-storage and storage during two successive campaigns in 2020 and 2021, the aim of which is to determine the risk for the Tunisian population. Then, we tried to evaluate the decontamination power of these mycotoxins in vitro by the use of lactic acid bacteria (LAB) and Bentonite (BT) and to study the toxicity of these mycotoxins and the capacity of these bio- products to prevent their toxicity in vivo.The multi-mycotoxin analysis of wheat samples clearly shows that the wheat sector in Tunisia is contaminated by aflatoxin B1 (AFB1) and/or enniatins A1, B, B1. AFB1 contaminated stored wheat samples more frequently and all concentrations determined exceed the acceptable dose limit (2 µg/kg). However, enniatins A1 and B were detected at the different wheat collection points and in the 2 sampling regions (continental and coastal). During both years of sampling, enniatin B was the most frequently found mycotoxin, followed by enniatin B1 and enniatin A1. All samples collected had a water activity less than 0.7 and the moisture content ranged from 9 to 14%, indicating that the presence of mycotoxins in the wheat samples was the result of previous contamination by factors promoting fungal infection and mycotoxin production (climatic conditions, farmers' cultivation practices and storage conditions). The concentrations of AFB1 and the co-occurrence of mycotoxins in durum wheat samples reported in this study represent a health risk for Tunisian consumers. For the in vitro study, the results revealed that the 3 Lactobacillus used, L. plantarum MON03 (LP), L. paracasei BEJ01 (LB), L. rhamnosus GAF06 (LR) and BT, showed an ability to eliminate mycotoxins (AFB1, AFM1, OTA and ZEN) in the different conditions tested. Then, according to IC50, the data did not reflect the toxicity of BT or LP on Vero cells, Caco-2 cells, C5-O cells, HepG2 and human leukocytes. LP and/or BT protected Caco-2 cells by inhibition of DNA fragmentation and reduction of caspase-3 enzymatic activity in ZEN- and AFB1-treated Caco-2 cells .The in vivo study confirmed the toxicity of AFM1 which is a metabolite of AFB1 on the various biological parameters tested. In the liver and kidneys, the triggering of oxidative stress as well as histological alterations provide evidence of the hepatotoxicity and nephrotoxicity of AFM1 in mice. This toxin also showed an immunotoxic effect by reducing the viability of splenocytes and thymocytes as well as modifications in the cellular and humoral immune response in mice. It also emerged that reproductive function was affected by AFB1 and ZEN which were found to be capable of altering spermatogenesis. Co-treatment with different mycotoxins and BT and/or LAB was able to reduce the toxic effects recorded in mice.As a conclusion, LAB and/or BT can be considered as two candidates in the biotechnology of detoxification of foods contaminated by mycotoxins in cattle farms and the agro-food industry.