Characterization of an epilactose-producing cellobiose 2-epimerase from Clostridium sp. TW13 and reutilization of waste milk

A novel cellobiose 2-epimerase gene ( CsCEase1 ) from Clostridium sp. TW13 was successfully overexpressed. Cs CEase1, with a molecular mass of 45.0 kDa, exhibited a specific activity of 254.75 U/mg and showed optimal activity at 40 °C and pH 7.5. Using Cs CEase1, 44.30 % of lactose was converted into epilactose, yielding a production level of 26.58 g/L. An efficient purification method was developed, incorporating crystallization and β-galactosidase treatment to remove the unconverted lactose, while Saccharomyces cerevisiae was used to consume the produced glucose. Final purification with activated carbon resulted in epilactose with 98 % purity and a recovery rate of 66.47 %. Furthermore, Cs CEase1 was incubated with whey power and expired milk, achieving epilactose conversion rates of 29.65 % and 32.69 %, respectively. These findings highlight the potential of Cs CEase1 for the cost-effective and environmentally sustainable production of epilactose from dairy waste.