# A catalytic membrane approach as a way to obtain sweet and unsweet lactose-free milk

## TL;DR

This paper presents a catalytic membrane method to produce lactose-free milk that is either sweet or unsweet, addressing the needs of lactose-intolerant consumers.

## Contribution

The study introduces a novel catalytic membrane approach using immobilized enzymes for efficient lactose hydrolysis and glucose decomposition.

## Key findings

- Free enzymes achieved lactose hydrolysis in 1 hour and glucose decomposition in 4.3 hours.
- Catalytic membranes made from regenerated cellulose and polyamide allowed enzyme reuse for up to 5 and 10 cycles, respectively.
- Immobilized enzymes extended the time required for bioconversion compared to free enzymes.

## Abstract

The growing need in the current market for innovative solutions to obtain lactose-free (L-F) milk is caused by the annual increase in the prevalence of lactose intolerance inside as well as the newborn, children, and adults. Various configurations of enzymes can yield two distinct L-F products: sweet (β-galactosidase) and unsweet (β-galactosidase and glucose oxidase) L-F milk. In addition, the reduction of sweetness through glucose decomposition should be performed in a one-pot mode with catalase to eliminate product inhibition caused by H2O2. Both L-F products enjoy popularity among a rapidly expanding group of consumers. Although enzyme immobilization techniques are well known in industrial processes, new carriers and economic strategies are still being searched. Polymeric carriers, due to the variety of functional groups and non-toxicity, are attractive propositions for individual and co-immobilization of food enzymes. In the presented work, two strategies (with free and immobilized enzymes; β-galactosidase NOLA, glucose oxidase from Aspergillus niger, and catalase from Serratia sp.) for obtaining sweet and unsweet L-F milk under low-temperature conditions were proposed. For free enzymes, achieving the critical assumption, lactose hydrolysis and glucose decomposition occurred after 1 and 4.3 h, respectively. The tested catalytic membranes were created on regenerated cellulose and polyamide. In both cases, the time required for lactose and glucose bioconversion was extended compared to free enzymes. However, these preparations could be reused for up to five (β-galactosidase) and ten cycles (glucose oxidase with catalase).

The online version contains supplementary material available at 10.1007/s00449-024-03018-z.