Enzymatic synthesis of calcium lactobionate from cheese whey permeate as a value-added ingredient

Lactobionic acid (LBA) and its salt form (e.g., lactobionate [LBN]) have emerged as high-value-added functional ingredients in food and pharmaceutical applications, such as acidulant, antioxidant, metal chelator, and carrier in drug delivery systems. Enzymatic oxidation has been employed as a nontoxic, cost-effective, and environmentally friendly approach for the synthesis of LBA/LBN. The current study investigated, first, the feasibility of producing calcium lactobionate (Ca-LBN) via enzymatic oxidation using cheese whey permeate as a substrate at high concentration, and second, the bioactivity of the resulting Ca-LBN. The production experiment was performed using reconstituted cheese whey permeate solution (300 g·L^-1 lactose) as a substrate, Ca(OH)₂ as a titrant base, oxidase (dosage: 400 U·kg^-1 lactose), and catalase (dosage: 168,000 U·kg^-1 lactose) in a laboratory bioreactor. Target critical control parameters, such as pH 6.40; dissolved oxygen: 44%; and temperature: 38°C, were defined and monitored using an industrial human-machine interface (HMI) to ensure operational stability. The consumption of Ca(OH)₂ was used to calculate real-time molar conversion rate (MCR_RT) and accumulative molar conversion yield (MCY) according to the pH-stat method. Enzymatic oxidation reaction continued for 7 h, and MCY was observed at nearly 99%. The MCR_RT rapidly reached a plateau value of ∼470 mmol·h^-1 within 20 min of the process. The critical operational parameters remained controlled by the HMI cascade, suggesting that the process is scalable. The DPPH-radical scavenging and ferrous ion chelating activity of the obtained LBN could not be confirmed based on the colorimetric assays used in the present work; however, characterization processes need to be further optimized. The obtained knowledge may be applied to the scalable production of LBA/LBN, enabling higher yields and an efficient manufacturing process.