Design of immobilized biocatalyst and optimal conditions for tyrosol β-galactoside production

Tyrosol beta-galactoside (TG) is a phenylethanoid glycoside with proven neuroprotective properties. This work deals with its biocatalytic production from tyrosol and lactose usingAspergillus oryzae beta-galactosidase in immobilized form. Six commercial carriers were examined to find the optimal biocatalyst. Besides standard biocatalyst performance characteristics, adsorption of the hydrophobic substrate on immobilization carrier matrices was also investigated. The adsorption of tyrosol was significant, but it did not have adverse effects on TG production. On the contrary, TG yield was improved for some biocatalysts. A biocatalyst prepared by covalent binding of beta-galactosidase on an epoxy-activated carrier was used for detailed investigation of the effect of reaction conditions on glycoside production. Temperature had a surprisingly weak effect on the overall process rate. A lactose concentration of 0.83 M was found to be optimal to enhance TG formation. The impact of tyrosol concentration was rather complex. This substrate caused inhibition of all reactions. Its concentration had a strong effect on the hydrolysis of lactose and all products. Higher tyrosol concentrations, 30-40 g/L, were favorable as pseudo-equilibrium concentrations of TG and galactooligosaccharide were reached. Repeated batch results revealed excellent operational stability of the biocatalyst.

Automated summary

The study focuses on the biocatalytic production of Tyrosol beta-galactoside (TG) from tyrosol and lactose using Aspergillus oryzae beta-galactosidase in immobilized form. The adsorption of tyrosol on immobilization carrier matrices was significant but did not negatively impact TG production, and even improved TG yield for some biocatalysts. Temperature had a weak effect on the overall process rate, while a lactose concentration of 0.83 M was found optimal for enhancing TG formation. Tyrosol concentration was complex, causing inhibition of reactions but higher concentrations proved favorable for reaching pseudo-equilibrium concentrations of TG and galactooligosaccharide. Repeated batch results showed excellent operational stability of the biocatalyst.