Consumption of fumonisin contaminated foods has a negative influence on the health of both humans (causing tumours in the liver and kidneys, well known for oesophageal cancer in Eastern Cape in South Africa) and animals (leucoencephalomalacia in horses). Lactic acid bacteria (LAB) have emerged as a promising natural detoxification agent against mycotoxins.The aim of this study was to visualize the interaction between fumonisins (fumonisin B1 (FB1) and fumonisin B2 (FB2)) and LAB, namely Lactobacillus plantarum FS2, L. delbrueckii subsp. delbrueckii CIP 57.8T and Pediococcus pentosaceus D39, isolated from traditional fermented maize-based products (ogi and mahewu) using confocal laser scanning microscopy (CLSM) and to then quantify the LAB-bound fumonisin using high performance liquid chromatography (HPLC). The objective was to obtain a physically visible and quantifiable binding interaction between fumonisins and LAB strains (viable and non-viable cells) with the aim of utilising LAB as a possible detoxifying agent. Fumonisins were derivatized using naphthalene-2, 3-dicarboxaldehyde (NDA) and then combined with non-fluorescent LAB cells (viable and non-viable). For the quantification of bound fumonisins, viable and nonviable cells were incubated in presence of predetermined concentrations of fumonisins and the level of fumonisin in the suspension was determined. Confocal scanning microscopy showed the derivatized green fluorescent fumonisins binding to the surface of each of the LAB cells.For viable cells, L. plantarum FS2 bound FB1 most effectively while P. pentosaceus D39 bound the least level of FB1. The highest levels of FB2 were bound by L. plantarum R 1096 and the least by L. delbrueckii CIP 57.8 T. For non-viable cells L. plantarum FS2 was also the most effective for binding both fumonisins with P. pentosaceus D39 and L. delbrueckii CIP 57.8 T being the least effective for FB1 and FB2, respectively. To our knowledge, this is the 2 first study to visualize the interaction between LAB and fumonisins. We demonstrate that LAB isolates from indigenous fermented maize based beverages bind fumonisins and thus present a potential strategy for their reduction in these traditional foods.

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Abstract:Maize, which contributes a large portion of the African diet and serves as the base substrate for many fermented cereal products,has been reported to be contaminated with fumonisins. This study aimed to evaluate in vitro the ability of predominant lactic acid bacteria (LAB) in African traditional fermented maize based foods (ogi and mahewu) to bind fumonisins B1 (FB1) and B2(FB2),as well as the stability of the complex at different pH and temperatures, in particular observed during ogi fermentation and under its storage conditions (time, temperature). The percentage of bound fumonisins was calculated after analysing the level of fumonisins not bound to LAB after a certain incubation time, by high performance liquid chromatography. The results revealed the ability of all tested LAB strains to bind both fumonisins, with binding efficiency varying between strains and higher for FB2. Binding of fumonisins increased with a decrease in pH from 6 to 4 (observed during ogi fermentation process) and from 4 to 2 (acidic pH in the stomach), and an increase in temperature (from 30°C to 37°C). The percentage of fumonisins (B1 and B2) bound to LAB at pH 4 decreased after 6 days of storage at 30°C for all LAB strains, except for L. plantarum (R1096) for which it increased. Lactobacillus species (L. plantarum and L. delbrueckii) were the most efficient in binding fumonisins (B1 and B2), whereas Pediococcus sp. the less efficient. Therefore, the Lactobacillus strains tested in this study can be recommended as potential starter cultures in African traditional fermented maize based foods to provide detoxifying and probiotic properties.