Investigation of different yeast strains for the detoxification of ochratoxin A.

High concentrations of ochratoxin A (OTA) in feed lead to growth depression in animals. It has been reported that binders can be used for deactivating aflatoxins but not for other mycotoxins without negatively influencing the animals health. In this study a strain from the genus ofTrichosporon with the ability to cleave ochratoxin A very selectively into phenylalanine and the non-toxic ochratoxin α (OTα) could be isolated. This strain was selected from a pool of OTA detoxifying microorganism by carrying out several investigations.Trichosporon sp. nov. can be fermented and stabilized. In a feeding trial with broilers lyophilizedTrichosporon-cells could compensate performance losses caused by OTA.

Structural characterization of metabolites after the microbial degradation of type A trichothecenes by the bacterial strain BBSH 797.

Contamination of feed with trichothecenes, a group of Fusarium mycotoxins, leads to losses in performance due to their immunosupressive effects and the negative effect on the gastrointestinal system in animal production. A possible way of detoxification is microbial degradation, which was the focus of this study. A bacterial strain--BBSH 797--which can degrade some mycotoxins of the trichothecene group, has already been isolated. It transforms deoxynivalenol (DON) into its metabolite DOM-1, the non-toxic deepoxide of DON. Analogous to the microbial degradation of DON, the transformation of six different type A trichothecenes was observed. The metabolites appearing were characterized by GC-MS after derivatization with TRI-SIL TBT. Two metabolites were additionally, identified by liquid chromatography-mass spectrometry with particle beam interface (LC-PB-MS) with electron impact (EI)-ionization mode. The major finding was that scirpentriol was completely transformed into its non-toxic metabolite deepoxy scirpentriol, while the mycotoxin T-2 triol underwent a more complicated metabolism. According to the study, T-2-triol was degraded into its non-toxic deepoxy form and into T-2 tetraol, which was then further metabolized to deepoxy T-2 tetraol. GC-MS after derivatization with TRI-SIL TBT was suitable for the structural characterization of trichothecenes and their degradation products. Besides the mass spectra of already known degradation products, spectra of new metabolites could be recorded by LC-PB-MS.

Feeding OTA to pigs: Analytical evaluation of a trial.

Methods were developed to analyse the concentrations of ochratoxin A (OTA) and its main metabolite ochratoxin α in blood plasma of pigs and in their kidneys. By the use of these methods blood and kidneys of pigs that were fed contaminated feedstuff containing 1500 µg/kg ochratoxin A for the whole trial period of 42 days were analysed.High levels of 1500 - 2000 µg/I OTA were found in the plasma, while the concentration of OTA in the kidneys did not exceed 250 µg/kg at the end of the trial. Neither in the plasma nor in the kidneys of the animals fed contaminated feedstuff ochratoxin a could be detected.

Evidence of ochratoxin A-detoxification activity of rumen fluid, intestinal fluid and soil samples as well as isolation of relevant microorganisms from these environments.

Dietary ochratoxin A (OTA) has a negative impact on performance of chickens and pigs. To avoid losses in animal production through intake of this mycotoxin and to prevent carry over to humans, strategies for counteracting have to be developed. In contrast to physical and chemical detoxification methods inactivation of ochratoxins by enzymatic reactions represent a very specific and gentle process. For the development of a new feed additive various environments have been screened for microorganisms with the capability of degrading or of cleaving the phenylalanine-moiety of ochratoxin A. Two OTA-degrading bacterial strains were isolated from rumen fluid and four pure cultures capable of cleaving ochratoxin A were obtained from pig intestine. The highest number of ochratoxin A degrading strains were found amongst aerobic bacteria which have mainly been isolated from soil.

Monitoring of residues of ochratoxin A in blood and kidney of chicken using HPLC-FLD.

Detoxification of ochratoxin A can be achieved by chemical or enzymatic hydrolyzation, the products of such reactions are ochratoxin α and phenylalanine. Ochratoxin α like ochratoxin A, is a fluorescing molecule, therefore sensitive analysis is possible at very low concentration levels. Methods have been established that make it possible to look for residues of ochratoxin A and its main metabolite ochratoxin α in blood and tissues at very low concentration levels. Plasma is extracted by the use of small amounts of chloroform; the extract is cleaned with water and afterwards evaporated to dryness]. The residue is re-dissolved and analysed by HPLC-FLD. Using this method a limit of detection of 0.5µg/l for both ochratoxin A and ochratoxin α can be reached.

Characterisation of metabolites after the microbial degradation of A- and B-trichothecenes by BBSH 797.

This work deals with the characterisation of trichothecene metabolites after the microbial degradation by the bacterial strain BBSH 797. Besides deoxynivalenol (DON), also the degradation of other trichothecenes was investigated. In the case of nivalenol, its metabolite deepoxy nivalenol could be identified. Useful methods for the structural characterisation are GC-MS or LC-PB-MS which were used in this particular case.