A novel cellobiose 2-epimerase from glacial psychrotolerant Arcticibacter eurypsychrophilus for the efficient production of epilactose at low temperatures

Cellobiose 2-epimerase (CE) has garnered significant attention for its capability to catalyze the biotransformation of lactose into epilactose, a prebiotic derivative. To date, about 30 distinct species sources of CE have been identified. In this study, a novel CE (Areu-CE) was identified from the psychrotolerant bacterium Arcticibacter eurypsychrophilus , isolated from glaciers on the Tibetan Plateau. This represents the first CE identified from a psychrotolerant species. Areu‑CE exhibits optimal activity at 50 °C toward lactose, achieving a specific activity of 139.7 U mg −1 and a catalytic constant (k cat ) of 169.8 s −1 , reflecting its robust epimerization capability. It also possesses notable substrate affinity, with a K m of 97.8 mM. Importantly, Areu-CE retains substantial activity at 8 °C, yielding 27% epilactose production at a protein concentration of 0.02 mg/mL when utilizing various concentrations of lactose and milk as substrates. These results highlight the potential of Areu-CE for cold-temperature epilactose production and support the value of glacier-derived microorganisms as a resource for cold-active enzyme discovery.