Comparative study of extracellular and intracellular β‐glucosidases of a new strain of Zygosaccharomyces bailii isolated from fermenting agave juice

A yeast strain isolated in the laboratory was studied and classified as a Zygosaccharomyces bailii. Both intracellular and extracellular β‐glucosidases of this yeast were purified by ion‐exchange chromatography, gel filtration and hydroxylapatite (only for the intracellular enzyme). The tetrameric structure of the two β‐glucosidases was determined following treatment of the purified enzyme with dodecyl sulphate. The intracellular β‐glucosidase exhibited optimum activity at 65°C and pH 5.5. The extracellular enzyme exhibited optimum catalytic activity at 55°C and pH 5. The molecular mass of purified intracellular and extracellular β‐glucosidases, estimated by gel filtration, was 440 and 360 kDa, respectively. Both enzymes are active against glycosides with (1 → 4)‐β, (1 → 6)‐β and (1 → 4)‐α linkage configuration. The intracellular enzyme possesses (1 → 6)‐α‐arabinofuranosidase activity and extracellular enzyme (1 → 6)‐α‐rhamno‐pyranosidase activity. The two β‐glucosidases are competitively inhibited by glucose and by D‐gluconic‐acid‐lactone and a slight glucosyl transferase activity is observed in the presence of ethanol. Since the glycosides present in wine and fruit juices represent a potential source of aromatic flavour, the possible use of the yeast β‐glucosidases for the liberation of the bound aroma is discussed.