Abstract
The reaction system for octyl-β-glucoside synthesis catalysed by the almond-β-glucosidase has been characterised. The monophasic octanol saturated with different amounts of water served as a reaction medium. Both the glucose and the activated substrate p-nitrophenyl-β-glucoside were examined as glycon donors. The reverse hydrolysis and the transglycosylation were both used as reaction models for this enzymatically catalysed alkyl-β-glucoside synthesis. The rate of synthesis of octyl-β-glucoside (vS), the rate of hydrolysis, i.e. the glucose formation (vH) and the predicted yield (Y) were determined. The effect of water activity on the synthetic and hydrolytic activity of the enzyme was investigated. Both the rate of synthesis and the rate of hydrolysis increased with the increase of the water activity in the reaction system, showing their maximum values at the water activity close to the saturation level. Thus, the maximum ratio of vS/vH=0.165 was achieved at the water activity of 0.94. The predicted yields were 0.5, 0.75 and 14.19% and were lower than the actually achieved yields of 19.45, 38 and 36.40% at the water activities of 0.75, 0.84 and 0.94, respectively. The yield of octyl-β-glucoside in the reverse hydrolysis was only 15.2%, i.e. 3.25 times lower than the yield obtained in the transglycosylation reaction with the water activity of 0.94. The solubility of glucose in pure octanol was only 1.5 mmol/L at the saturation level of 12 mmol/L in the presence of 10 mmol/L of p-nitrophenyl-β-glucoside, and it increased to 15.5 mmol/L in the presence of octyl-β-glucoside.
Highlights
Clean production of chemicals or the so-called green chemistry is an environmentally friendly area of chemistry and it refers to a design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances [1]
The reverse hydrolysis and the transglycosylation were both used as reaction models for this enzymatically catalysed alkyl-β-glucoside synthesis
The almond β-glucosidase was used as a catalyst for octyl-β-glucoside synthesis via a transglycosylation reaction
Summary
Clean production of chemicals or the so-called green chemistry is an environmentally friendly area of chemistry and it refers to a design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances [1]. It is characterised with: minimal waste production, minimal energy consumption, efficient raw material use such as that of renewable resources. Enzymatic synthesis of biosurfactants belongs to this kind of processes and biosurfactants are certainly products that are extremely environmentally friendly due to their biocompatibility and biodegradability. The chemical route for their synthesis involves extremes of temperature, pressure, use of toxic catalysts, and multiple steps of protection, deprotection and activation. β-Glycosidases pro-
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