The catalytic potency of β-glucosidase from Pyrococcus furiosus in the direct glucosylation reaction

Preparation and Properties of Gelatin-Immobilized β-Glucosidase fromPyrococcus furiosus

Hyperthermostable beta-glucosidase from Pyrococcus furiosus was enclosed in gelatin gel by cross-linking with transglutaminase. Gelatin-immobilized beta-glucosidase was considerably more thermostable than the native enzyme. Lyophilized immobilisate was stored at 90 degrees C for 1 month without loss of activity. The immobilized beta-glucosidase catalyzed transglucosylation of 5-phenylpentanol with 10.0 equivalent of cellobiose at pH 5.0 and 70 degrees C for 12 h to afford 5-phenylpentyl beta-D-glucopyranoside in 41% yield. The immobilized enzyme was more effective than the native one in transglucosylation. The gelatin-immobilized Pfu-beta-glucosidase recovered from the first run of the reaction was reusable on successive runs.

Enzyme-catalyzed synthesis of heptyl-β-glycosides: effect of water coalescence at high temperature

Alkyl glycosides can be synthesized by glycosidases in organic media with limited amounts of water. These systems, however, limit the solubility of the sugar substrates and decrease reaction yields. Herein we report the enzymatic synthesis of heptyl-β-glycosides in heptanol catalyzed by a hyperthermophilic β-glycosidase at 90°C. Our results indicate that dispersion of water in heptanol changes with time producing coalescence of water at the bottom of the reactor, playing a key role in the reaction yield. Water-soluble substrate, enzyme and products are concentrated in the aqueous phase, according to their partition coefficients, promoting side reactions that inactivate the enzyme. Reaction yield of heptyl-β-glycosides was 35% relative to lactose, at 7% water. The increase in the water phase to 12% diminished the enzyme inactivation and increased the heptyl-β-glycosides yield to 52%. Surface-active compounds, SDS and octyl glucoside, increased water dispersion but were unable to prevent coalescence.

A new thermostable β-glucosidase mined from Dictyoglomus thermophilum: properties and performance in octyl glucoside synthesis at high temperatures

A new β-glucosidase (DtGH) representing 40% identity with an apple seed glycosidase (ASG) was cloned from Dictyoglomus thermophilum. DtGH showed extremely high thermostability in aqueous solution, with half-lives of 533, 44, and 5 h measured at 70, 80 and 90 °C, respectively. Therefore it was used for direct glycosylation of n-octanol at 70 °C instead of 50 °C as usually. As a result, the glucose based conversion was increased by 27%, but the time spent to reach equilibrium was decreased from 7 d to 3 d. This enzyme also exhibited excellent stability under the reaction environment, retaining 70-80% of its initial activity after 7 d of incubation at 70 °C in either 1.7 M glucose solution or octanol-aqueous (85:15, v/v) system. It could retain part of synthetic activity even in boiling water. Owing to the strong glucose-tolerance and extremely high thermostability, DtGH should be promising for various glucosides synthesis.