Fungus β-glycosidases: immobilization and use in alkyl-β-glycoside synthesis

Production of β-glycosidases: β-xylosidase and β-glucosidase by the fungus Sclerotinia sclerotiorum was optimized in the presence of different carbon sources. Immobilization supports with different physico-chemical characteristics were evaluated for use in continuous reactors. Immobilization and activity yields were calculated. Among the adsorption on Duolite, Amberlite, Celite and DEAE-sepharose, and entrapment in polyacrylamide gel or reticulation using glutaraldehyde, highest yields were obtained when β-xylosidase was adsorbed on Duolite A 7 and when β-glucosidase was adsorbed on DEAE-sepharose.

Enzyme preparations from S. sclerotiorum cultures were used in a biphasic (alcohol/aqueous) medium for the synthesis of alkyl-glycosides by trans-glycosylation of sugars and long-chain alcohols. The synthesis was studied under different conditions with primary and secondary alcohols as substrates, in the presence of free or immobilized enzyme. Xylan and cellobiose were used for the synthesis of alkyl-xylosides and alkyl-glucosides, respectively. The majority of the immobilized preparations were unable to catalyze the synthesis of alkyl-glycosides.

Highest yields were obtained when using xylan and C₄–C₆-alcohols. The reaction produced alkyl-β-xyloside and alkyl-β-xylobioside, as confirmed by MS/MS. Up to 22 mM iso-amyl-xyloside and 14 mM iso-amyl-xylobioside were produced from iso-amyl alcohol and xylan.