The presented work involves obtaining and characterising a two-enzymatic one-pot bioreactor, including encapsulated (co-immobilised) glucose oxidase and catalase. The enzymatic capsules were applied to produce unsweet, lactose-free milk during low-temperature catalysis. Furthermore, operational conditions, like pH and aeration, were selected in the paper, which sorts out discrepancies in literature reports. All experiments were carried out at 12 °C, corresponding to milk storage and transportation temperature. Preliminary studies (for reasons of analytical accuracy) were carried out in a buffer (pH, concentration of sugars mimicking conditions in the lactose-free milk, the initial glucose concentration 27.5 g/L) verified by processes carried out in milk in the final stage of the study. The presented results showed the need for regulating pH and the aeration of the reaction mixture in the continuous mode during the process. The procedure of co-immobilisation was performed in an alginate matrix with the cross-linking of glutaraldehyde or carbodiimide while carbodiimide showed better enzymes retention inside alginate capsules. Co-encapsulated enzymes could be used for nine cycles, preserving finally about 40% of the initial activity.
Keywords: catalase; chemical cross-linking of the hydrogel; co-encapsulation; glucose oxidase; low-temperature biocatalysis; one-pot processes; reaction mixture aeration; unsweet lactose-free milk.