Synthesis of Lactose-Derived Nutraceuticals from Dairy Waste Whey—a Review

Due to stricter environmental legislation and implementation of the “waste valorization” concept, recycling of dairy effluent, whey, has drawn a considerable attention. The main constituent of whey is lactose, which is responsible for high biological oxygen demand (BOD) and chemical oxygen demand (COD) values. Therefore, without going to its direct disposal into aquatic system, synthesis of nutraceuticals from lactose is considered a commendable challenge. Lactose-derived nutraceuticals, such as galacto-oligosaccharide (GOS), lactulose, lactitol, lactosucrose, lactobionic acid, gluconic acid, lactone, and tagatose, have been synthesized through different chemical and biochemical reactions, such as hydrolysis, transgalactosylation, oxidation, reduction, isomerization, and hydrogenolysis, considering raw whey or isolated lactose as feedstock. Pure biocatalyst (enzyme) and inorganic catalyst have been used for the synthesis of lactose-based nutraceuticals by different types of operations, such as conventional batch and continuous bioreactors with free catalyst, continuous packed bed bioreactor with immobilized catalyst, moving bed reactor, and membrane-assigned bioreactor. Moreover, in many cases, lactose-based nutraceuticals (lactic acid, lactosucrose, lactobionic acid, gluconic acid, and tagatose) have been synthesized by microbial fermentation process. Free microbial cell in batch and continuous fermentor and whole cell immobilized packed bed bioreactor have been used for this purpose. This review presents and compares different process-related technological aspects for synthesis of lactose-derived nutraceuticals from whey.