A Versatile Family 3 Glycoside Hydrolase from Bifidobacterium adolescentis Hydrolyzes β-Glucosides of the Fusarium Mycotoxins Deoxynivalenol, Nivalenol, and HT-2 Toxin in Cereal Matrices

Abstract

Infestation of cereals by phytopathogenic fungi is a global threat to the human food supply. In addition to economically devastating losses through yield and quality deterioration of agricultural products, contamination with mycotoxins poses a serious challenge for food safety (1). Among the most relevant mycotoxin producers worldwide are Fusarium species, causing Fusarium head blight disease of small-grain cereals (FHB; also known as Fusarium ear blight or scab). Trichothecene class mycotoxins inhibit eukaryotic protein synthesis and are important Fusarium virulence factors. Furthermore, they can cause apoptotic cell death and immunosuppression and trigger proinflammatory responses in humans and animals (1-3). The most important groups with regard to food safety are type A (T-2 toxin and HT-2 toxin [HT2]) and type B (nivalenol [NIV] and deoxynivalenol [DON]) trichothecenes (4). The type A trichothecene T-2 toxin possesses high acute toxicity and has caused fatal outbreaks of alimentary toxic aleukia in the last century (1). DON is the predominant trichothecene toxin produced by the Fusarium graminearum species complex and ranks among the most frequent contaminants of cereals. Although the acute toxicity of DON is lower than that of type A trichothecenes, its ubiquitous presence in Fusarium-infected cereals creates an important food safety issue (2). Acute symptoms of DON ingestion are gastroenteritis and emesis (hence, the colloquial term vomitoxin). Maximum levels for DON in cereal-based foodstuff are set in Commission Regulation 1881/2006 (5), and indicative levels are provided for the sum of T-2 toxin and HT-2 toxin in Commission Recommendation 2013/165/EU (6) in Europe to protect consumers.The glycosylation of small molecules is a major route to inactivate endogenous and exogenous (xenobiotic) metabolites in plants (7-9). For example, formation of DON-3-O-␤-D-glucopyranoside (DON-3G) is an important factor in plant defense against FHB and has been proposed to be the molecular basis of the still-unidentified FHB1 gene (Fusarium head blight resistance quantitative trait locus) in wheat (10). DON-3G has been detected in a wide range of cereal commodities, with concentrations of about 20% relative to that of DON (11,12). However, high regional and seasonal variations have been reported, and in some cases, the content of DON-3G even exceeded that of DON (13,14). Evidence for glucosylated metabolites of NIV and type A trichothecenes has been presented as well (15)(16)(17). Such glucoconjugates of plant origin have been termed masked mycotoxins (13, 18), implying that they escape detection through

Porcine Small and Large Intestinal Microbiota Rapidly Hydrolyze the Masked Mycotoxin Deoxynivalenol-3-Glucoside and Release Deoxynivalenol in Spiked Batch Cultures In Vitro

“…The current study focused on a quantitative and qualitative analysis of the intestinal microbiota of the porcine intestine but did not identify specific bacterial groups involved in the hydrolysis of DON3Glc. Published work has identified bacteria from very different genera and phyla (lactobacilli, enterococci, bifidobacteria) that are capable of hydrolyzing DON3Glc and other masked mycotoxins (27,28), and future studies are required to understand their contribution to hydrolysis in mixed microbial communities and in vivo.…”

Synthesis of Mono- and Di-Glucosides of Zearalenone and α-/β-Zearalenol by Recombinant Barley Glucosyltransferase HvUGT14077

“…After 4 h, the batch was frozen at −20 °C and stored until LC-MS/MS results were available. Afterwards, this batch was used to biocatalytically increase the ZEN-16-G proportion (sum of ZEN/ZEN-glucosides 1.5 mM in reaction), by adding a β-glucosidase from Lactobacillus brevis [ 56 ] with 0.8–24 µg·mL −1 in preliminary assays and 24 µg·mL −1 in a final batch. Fresh Hv UGT14077 and At SUS1 for UDP-glucose recycling were added to final concentrations of 1.25 mg·mL −1 each.…”

Do Plant-Bound Masked Mycotoxins Contribute to Toxicity?

“…The identity and toxicity of these metabolites remains to be elucidated. Kinetic studies with purified recombinant glycosyl hydrolase (GH3) enzymes derived from Lactobacillus brevis and Bifidobacterium adolescentis showed significantly slower kinetics for the hydrolysis of NIV3Glc compared to DON3Glc, although assays were performed at 10-fold lower concentrations [40]. Regarding masked ZEN compounds, ZEN14Glc, ZEN14S, as well as α- and β-ZEL14Glc are all very rapidly hydrolyzed by mixed fecal microbiota with recovery of intact masked compounds dropping below 20%–40% after 30 min of incubation [26,28].…”