In Vitro Reduction of Extractable Zearalenone and Screening of Tentative Transformation Products by Metschnikowia pulcherrima KKP 1368 Under Selected Buffered pH Conditions Relevant to the Porcine Gastrointestinal Tract

Zearalenone (ZEN) is an estrogenic mycotoxin produced by Fusarium spp. and commonly found in cereals and feed materials. This study evaluated the ability of Metschnikowia pulcherrima KKP 1368 biomass to reduce extractable ZEN under controlled buffered pH conditions (pH 3.50 and 7.00) selected as simplified conditions relevant to the porcine gastrointestinal environment. ZEN was quantified by LC-MS/MS, whereas LC-MS-QTOF was used as a qualitative/semi-quantitative screening approach for tentatively assigned transformation-related features. In the presence of yeast biomass, extractable ZEN was already lower than in the corresponding controls at the first sampling point, indicating a rapid biomass-associated effect. After 12 h, reductions relative to the corresponding controls reached 63.0% at pH 3.50 (p < 0.0001) and 51.6% at pH 7.00 (p = 0.0001). ZEN remained stable in control samples, and the strain remained viable under both pH conditions throughout incubation. LC-MS-QTOF detected several tentatively assigned features consistent with zearalanone, zearalenone-14-glucuronide, and zearalenol O-glucoside; these assignments require confirmation with authentic standards. Overall, M. pulcherrima KKP 1368 reduced extractable ZEN in a simplified buffered in vitro system, probably through rapid adsorption/reduced extractability and possible biotransformation. Further studies using biomass fractions or inactivated biomass, mass-balance experiments, authentic standards, and toxicological assays are needed to clarify the relative contribution of adsorption and transformation and to assess the practical relevance of this approach.