Abstract
Ochratoxin A (OTA) is one of the most important mycotoxins, and contaminates several agricultural products, particularly cereals, grapes, maize, barley, spices and coffee. The aim of this project was to reduce the levels of OTA by supplementing the artificially contaminated solutions with seven strains of actinobacteria (AT10, AT8, SN7, MS1, ML5, G10 and PT1) in order to evaluate their capacity for binding and metabolizing the OTA, as well as their ability to reduce the expression of the genes responsible for its production in A. carbonarius. In the first part of this study, we evaluated the capacity of Streptomyces strains for binding OTA on their surfaces after 0, 30 and 60 min of incubation with PBS solution supplemented with OTA. In the second part, we tested the ability of these strains, as well as their supernatants, to detoxify the ISP2 medium. Finally, we studied the effect of the Streptomyces cocultured with Aspergillus carbonarius on the expression of OTA biosynthesis genes. Results showed that, among the strains co-cultured with A. carbonarius, the strain G10 was able to reduce the expression of acpks, acOTApks, acOTAnrps and vea genes, thus reducing OTA from solid PDA medium to 13.50% of reduction. This strain was remarkably able to detoxify and bind OTA up to 47.07%. Strain AT8 was stronger in detoxifying OTA (52.61%), but had no significant effect on the studied gene expression.
Highlights
Ochratoxin A (OTA) is a secondary metabolite produced by molds of the genera Aspergillus and Penicillium on several food commodities in pre- and post-harvest conditions [1,2,3]
Kinetics of OTA Binding to Actinobacterial Cell Wall
Since this study was handled in a non-nutritive solution (PBS), the observed reductions could not be attributed to an enzymatic activity of the actinobacteria
Summary
Ochratoxin A (OTA) is a secondary metabolite produced by molds of the genera Aspergillus and Penicillium on several food commodities in pre- and post-harvest conditions [1,2,3]. Others have been focused on treating the contaminated food with living organisms such as lactic acid bacteria (LAB) and yeasts, to reduce the OTA concentration. This biological decontamination is either performed by OTA biodegradation using microorganisms and Toxins 2017, 9, 222; doi:10.3390/toxins9070222 www.mdpi.com/journal/toxins. Toxins 2017, 9, 222 their enzymes [9,10,11], or by binding the toxin on the cell wall surface of these microorganisms [12,13,14] Both approaches help reduce OTA without significant losses in nutritive values, since no harmful chemicals are used in this treatment of contaminated food [15,16,17,18]. Turbic, et al [20] claimed that OTA reduction by Lb. rhamnosus strains (76% of reduction) was caused by the adsorption of this toxin onto the LAB cell walls, since the acid-treated bacteria were more effective for removing OTA than the viable ones after 2 h at 37 ◦ C
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