Physical Adsorption of Aflatoxin B1 by Lactic Acid Bacteria and Saccharomyces cerevisiae: A Theoretical Model

Abstract

The ability of lactic acid bacteria (LAB) and Saccharomyces cerevisiae to remove aflatoxin B1 (AFB1) from liquid medium was tested. The experimental results indicated that (i) AFB1 binding to microorganisms was a rapid process (no more than 1 min); (ii) this binding involved the formation of a reversible complex between the toxin and microorganism surface, without chemical modification of the toxin; (iii) the amount of AFB1 removed was both toxin- and bacteria concentration-dependent; and (iv) quantitatively similar results were obtained with viable and nonviable (heat-treated) bacteria. According to these details, a physical adsorption model is proposed for the binding of AFB1 to LAB and S. cerevisiae, considering that the binding (adsorption) and release (desorption) of AFB1 to and from the site on the surface of the microorganism took place (AFB1 + S <--> S - AFB1). The model permits the estimation of two parameters: the number of binding sites per microorganism (M) and the reaction equilibrium constant (K(eq)) involved, both of which are useful for estimating the adsorption efficiency (M x K(eq)) of a particular microorganism. Application of the model to experimental data suggests that different microorganisms have similar K(eq) values and that the differences in toxin removal efficiency are mainly due to differences in M values. The most important application of the proposed model is the capacity to select the most efficient microorganism to remove AFB1. Furthermore, it allows us to know if a modification of the adsorption efficiency obtained by physical, chemical, or genetic treatments on the microorganism is a consequence of changes in M, K(eq), or both.

Binding of Aflatoxin B1 to Lactic Acid Bacteria and Saccharomyces cerevisiae in vitro: A Useful Model to Determine the Most Efficient Microorganism

“…Then, the bacteria were incubated for 30 min at 37°C and pelleted by centrifugation. The supernatant was collected for free AFB 1 analysis by HPLC according to Bueno et al (2007). AFB 1 bound to cells was calculated as the difference between the total AFB 1 and the amount of free AFB 1 .…”

“…The first step in this direction is the selection of the most efficient microorganism for AFB 1 removing and while many researchers have assayed LAB and yeast with AFB 1 binding abilities (Ciegler et al, 1966;El-Nezami et al, 1998;Gourama & Bullerman, 1995;Line et al, 1994;Oatley et al, 2000) no clear mechanism for this effect has been provided. Thus, this selection frequently is performed using a single concentration of AFB 1 , but we demonstrated that the microorganism efficiency may change when the mycotoxin concentration is modified (Bueno et al, 2007;Pizzolitto, 2011), therefore the microorganism selected could not be the most competent. In this context, we investigated the nature of the interaction between different microorganisms and AFB 1 molecule, which led us to develop a model to explain the binding of AFB 1 by LAB and Saccharomyces cerevisiae strains.…”

“…The inclusion of appropriate microorganisms in the contaminated diet could prevent the absorption of mycotoxins during their passage in the gastrointestinal tract and eliminated in the faeces (Bueno et al, 2007;El-Nezami et al, 2000;Gratz et al, 2004Gratz et al, , 2007. Moreover, Kankaanpää et al (2000) showed that the binding of AFB 1 to the surface of LAB reduced their adhesive properties, and the accumulation of aflatoxins in the intestine may therefore be reduced via the increased excretion of an aflatoxin-bacteria complex.…”

“…In this context, we investigated the nature of the interaction between different microorganisms and AFB 1 molecule, which led us to develop a model to explain the binding of AFB 1 by LAB and Saccharomyces cerevisiae strains. This model allows an estimation of two important parameters related to a microorganism's capacity for dietary decontamination: the number of binding sites for AFB 1 in the surface microorganism (M) and the equilibrium constant of the process involved (K eq ), both of them are useful in the selection of the most suitable microorganism in a wide range of AFB 1 concentration (Bueno et al, 2007). In adittion, studies of viability of the microorganisms in the salivary and gastrointestinal tract, cell adhesion, autoaggregation, coaggregation and antimicrobial activity against pathogen strains, were also evaluated as a way to research potential beneficial properties on the host (Armando et al, 2011).…”

Evidence Based Phytopharmacological Potential of Herbal Extracts in Post-Ingestion Management of Mycotoxins in Animal Models

“…The beneficial effects of Saccharomyces cerevisiae in management of aflatoxin B1 toxicity has also been evaluated in broilers [106] and Quails [107]. Bueno et al [108] has also demonstrated that Saccharomyces cerevisiae is an important and efficient micro-organism in aflatoxin B1 quenching. Moreover, it is suggested that Saccharomyces cerevisiae cell wall have glucan, they reduce the frequency of micro nuclei induced by cyclophosphamide.…”