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

Glycosylation plays a central role in plant defense against xenobiotics, including mycotoxins. Glucoconjugates ofFusarium toxins, such as deoxynivalenol-3-O -β-d -glucoside (DON-3G), often cooccur with their parental toxins in cereal-based food and feed. To date, only limited information exists on the occurrence of glucosylated mycotoxins and their toxicological relevance. Due to a lack of analytical standards and the requirement of high-end analytical instrumentation for their direct determination, hydrolytic cleavage of β-glucosides followed by analysis of the released parental toxins has been proposed as an indirect determination approach. This study compares the abilities of several fungal and recombinant bacterial β-glucosidases to hydrolyze the model analyte DON-3G. Furthermore, substrate specificities of two fungal and two bacterial (Lactobacillus brevis andBifidobacterium adolescentis ) glycoside hydrolase family 3 β-glucosidases were evaluated on a broader range of substrates. The purified recombinant enzyme fromB. adolescentis (Ba Bgl) displayed high flexibility in substrate specificity and exerted the highest hydrolytic activity toward 3-O -β-d -glucosides of the trichothecenes deoxynivalenol (DON), nivalenol, and HT-2 toxin. AKm of 5.4 mM and aV max of 16 μmol min−1 mg−1 were determined with DON-3G. Due to low product inhibition (DON and glucose) and sufficient activity in several extracts of cereal matrices, this enzyme has the potential to be used for indirect analyses of trichothecene-β-glucosides in cereal samples.