Reaction scale‐up and electrodialysis for lactobionic acid production from enzymatic lactose oxidation

Background Lactobionic acid is a valuable organic acid with various applications in food, cosmetics, pharmaceutical and medical industries. The enzymatic conversion of lactose in dairy side streams into lactobionic acid provides a sustainable valorisation method. Aims This study made use of two commercially available enzymes, LactoYIELD® and Catazyme®, with hydrogen peroxide for the bioconversion, testing three different scales. This was followed by conventional and simultaneous electrodialysis for the separation of lactobionic acid produced in ultrafiltration permeate in pilot‐scale experiments. Methods LactoYIELD® (cellobiose dehydrogenase) and Catazyme® (catalase) were used for lactose oxidation in ultrafiltration permeate. HPLC was used for lactose and lactobionic acid determination throughout oxidation and electrodialysis. Conventional electrodialysis was conducted with a pilot‐scale system with 50 pairs of anionic and cationic exchange membranes. In all electrodialysis experiments, 50 L UF permeate was used as a feed in the diluate tank and 10 L reverse osmosis (RO) water was used as the initial concentrate stream. Major Findings Slightly lower yields of lactobionic acid were found when scaled up to 25 and 50 L from the lab scale (0.2 L). Consecutive electrodialysis, in which the enzymatic reaction producing lactobionic acid was completed prior to electrodialysis, resulted in 84.4% removal of lactobionic acid with a final concentration of 67.56 mg/mL in the concentrate, while simultaneous processing yielded similar lactobionic acid concentrations (74.13 mg/mL). Consecutive and simultaneous processing had not only low energy consumptions (0.37–0.38 kWh/kg LBA) but also low current efficiencies (26.5–32.1%). Despite this, the simultaneous electrodialysis shows promise for industrial dairy waste valorisation. Industrial Implications The integrated enzymatic conversion and electrodialysis separation process provides a low‐energy, scalable approach for lactobionic acid production from side streams produced in the dairy industry. A brief discussion of the industrial and economic feasibility of the enzymatic oxidation and electrodialysis process was also included.