Microbial Detoxification of Deoxynivalenol (DON), Assessed via a Lemna minor L. Bioassay, through Biotransformation to 3-epi-DON and 3-epi-DOM-1

Abstract

Mycotoxins are toxic metabolites produced by fungi. To mitigate mycotoxins in food or feed, biotransformation is an emerging technology in which microorganisms degrade toxins into non-toxic metabolites. To monitor deoxynivalenol (DON) biotransformation, analytical tools such as ELISA and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) are typically used. However, these techniques do not give a decisive answer about the remaining toxicity of possible biotransformation products. Hence, a bioassay using Lemna minor L. was developed. A dose-response analysis revealed significant inhibition in the growth of L. minor exposed to DON concentrations of 0.25 mg/L and higher. Concentrations above 1 mg/L were lethal for the plant. This bioassay is far more sensitive than previously described systems. The bioassay was implemented to screen microbial enrichment cultures, originating from rumen fluid, soil, digestate and activated sludge, on their biotransformation and detoxification capability of DON. The enrichment cultures originating from soil and activated sludge were capable of detoxifying and degrading 5 and 50 mg/L DON. In addition, the metabolites 3-epi-DON and the epimer of de-epoxy-DON (3-epi-DOM-1) were found as biotransformation products of both consortia. Our work provides a new valuable tool to screen microbial cultures for their detoxification capacity.

Keywords: 3-epi-DON; 3-epi-de-epoxy-DON (3-epi-DOM-1); Lemna minor; bioassay; biotransformation; deoxynivalenol (DON); detoxification.

Figure 1

Growth of Lemna minor in response to deoxynivalenol (DON): (a) Data calculated based on number of fronds: correlation of growth and concentration DON (0–1 mg/L DON); (b) Data calculated based on number of fronds: correlation of logit growth and log concentration DON (0.0625–1 mg/L DON); (c) Data calculated based on frond area: correlation of growth and concentration DON (0–1 mg/L DON); (d) Data calculated based on frond area: correlation of logit growth and log concentration DON (0.0625–1 mg/L DON); (e) Response of Lemna minor after 7 days to increasing DON concentrations. Legend: black-white bar = 5 mm.

Figure 1

Growth of Lemna minor in response to deoxynivalenol (DON): (a) Data calculated based on number of fronds: correlation of growth and concentration DON (0–1 mg/L DON); (b) Data calculated based on number of fronds: correlation of logit growth and log concentration DON (0.0625–1 mg/L DON); (c) Data calculated based on frond area: correlation of growth and concentration DON (0–1 mg/L DON); (d) Data calculated based on frond area: correlation of logit growth and log concentration DON (0.0625–1 mg/L DON); (e) Response of Lemna minor after 7 days to increasing DON concentrations. Legend: black-white bar = 5 mm.

Figure 2

The calibration curve is expressed as the logit growth of number of fronds in function of the log concentration DON (mg/L). Data is shown from 0.125 to 1 mg/L DON. Triplicates of each experiment are illustrated in the same color.

Figure 3

Extracted ion chromatograms (XICs) of the samples at 50 mg/L DON soil and activated sludge after four weeks, including the control (medium and DON). DON and 3-epi-DON were detected as both the protonated molecules and sodium adducts. Only the XICs for the sodium adducts are shown.