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FT-IR spectroscopy applied to identification of functional groups on the surface of Gluconobacter oxydans involved in the bacteria–ochratoxin A interaction

Many microorganisms like yeasts, molds and bacteria can reduce or modify ochratoxin A (OTA) present in food and feed. The application of microorganisms as mycotoxin binders highly depends on stability of the microorganism-mycotoxin complex. The most important feature for mycotoxins binding is the specific surface properties of the microorganisms, cell physiology and properties of mycotoxins like polarity, solubility, shape and charge distribution. It is well known that bacterium Gluconobacter oxydans is able to degrade patulin but has not been tested previously for their ability to bind OTA. Therefore the main objective of the study was to determine if the G. oxydans can bound OTA using viable and heat-treated cells. The method used for quantitative determination of OTA was immunoassay ELISA method, whereas method used for confirmation of the OTA presence included more specific detection technique liquid chromatography tandem mass spectrometry (LC-MS/MS). Obtained results show that G. oxydans bound OTA efficiently, although binding percentages for the heat-treated cells were below the values obtained for viable cells. In experiments with heat-treated cells binding capacity of OTA decreased from 80.8 to 30.4%. Influence on the changes of the tested strain surface properties was investigated by Fourier Transform Infrared Spectroscopy (FT-IR) presenting technique to obtain spectra from a very wide range of different compounds and to identify types of chemical bonds in a molecule. FT-IR analysis showed that the cell wall plays a key role in OTA adsorption. The most significant difference in the FT-IR spectra of blank biomass and G. oxydans biomass loaded with OTA was observed in the region of proteins (amide A, amide I and amide II band of proteins).

FT-IR spectroscopy; Gluconobacter oxydans; ochratoxin A

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