Synthesis of the Galactosyl Derivative of Gluconic Acid With the Transglycosylation Activity of β-Galactosidase.

Bionic acids are bioactive compounds demonstrating numerous interesting properties. They are widely produced by chemical or enzymatic oxidation of disaccharides. This paper focuses on the galactosyl derivative of gluconic acid as a result of a new method of bionic acid synthesis which utilises the transglycosylation properties of β-galactosidase and introduces lactose as a substrate. Products obtained in such a process are characterised by different structures (and, potentially, properties) than those resulting from traditional oxidation of disaccharides. The aim of this study is to determine the effect of selected parameters (concentration and ratio of substrates, dose of the enzyme, time, pH, presence of salts) on the course of the reaction carried out with the enzymatic preparation Lactozym, containing β-galactosidase from Kluyveromyces lactis. Research has shown that increased dry matter content in the baseline solution (up to 50%, by mass per volume) and an addition of NaCl contribute to higher yield. On the other hand, reduced content of the derivative is a result of increased pH from 7.0 to 9.0 and an addition of magnesium and manganese salts. Moreover, exceeding the β-galactosidase dose over approx. 35 000 U per 100 g of lactose also leads to reduced yield of the process. The most favourable molar ratio of sodium gluconate to lactose is 2.225:0.675. Depending on the conditions of the synthesis, the product concentration ranged between 17.3 and 118.3 g/L of the reaction mixture, which corresponded to the mass fraction of 6.64-23.7% of dry matter. The data obtained as a result of the present study may be useful for designing an industrial process.