Effect of Selected Parameters of Lactose Hydrolysis in the Presence of β‐Galactosidase from Various Sources on the Synthesis of Galactosyl‐Polyol Derivatives

Abstract Galactosyl‐polyhydroxyalcohols are products of transgalactosylation occurring during lactose hydrolysis in the presence of polyols. Products of transgalactosylation (mainly galactooligosaccharides) are known for their health‐promoting properties. The aim of this research was to determine the conditions of the synthesis of selected gal‐polyols using enzymes from various sources: Kluyveromyces fragilis, Kluyveromyces lactis and Aspergillus oryzae . The highest amounts of galactosyl derivatives of polyol‐monomers (sorbitol, xylitol and erythritol), formed during the enzymatic hydrolysis of lactose with the use of the enzyme from K. lactis , were obtained using an initial solution of the molar ratio of lactose to polyol equal to 1:1.85. In the case of lactitol, this proportion amounted to 1:2.9. The best transgalactosylating properties in the course of the synthesis of gal‐sorbitol and gal‐erythritol were obtained with β‐galactosidase from K. fragilis ; where the contents of galactosyl derivatives in dry matter accounted for 16.4 % [w/w] and 18.8 % [w/w], respectively. The quantities of derivatives of xylitol and lactitol obtained through the application of enzymes from K. lactis and K. fragilis were comparable – up to 14.7 % [w/w] of gal‐xylitol and up to 17.2 % [w/w] of gal‐lactitol. Enzymes from yeasts showed a larger affinity towards the synthesis of derivatives of polyol‐monomers, whereas the enzyme from mould synthesized trimers faster. An excessive addition of enzymes brought about an intensification of gal‐polyol hydrolysis and a decrease of their content in the hydrolysates. Thus, the amount of β‐galactosidase to be added should not exceed 2500 AUL/100 mL in gal‐erythritol synthesis, 1300 AUL/100 mL in gal‐xylitol synthesis, 4000 AUL/100 mL in gal‐sorbitol synthesis a well as 2600 AUL/100 mL in gal‐lactitol synthesis.