Comparative Investigations on Different beta-Glucosidase Surrogate Substrates

beta-glucosidases are hydrolyzing enzymes which can release many aroma-active compounds from their glycoside form. Several yeasts produce these enzymes and thus are applied during the wine production process. To be able to test specific organisms for the presence of beta-glucosidases and to investigate this enzyme activity, four main surrogate substrates have been described. The properties and applicability of these compounds, named arbutin (hydroquinone-beta-D-glucopyranoside), esculin (6-O-(-D-glucosyl)aesculetin), 4-nitrophenyl-beta-D-glucopyranoside (pNPG) and 4-methylumbelliferyl-beta-D-glucopyranoside (4-MUG), are discussed after comparing their advantages and disadvantages. Although all four substrates were found suitable for photometric assays, 4-MUG has proven to be most appropriate due to high sensitivity, high robustness and simple processing. Furthermore, the investigation of beta-glucosidase product accumulation is described, which could be used to give indications about beta-glucosidase localization.