The valorization of cheese whey, a rich by-product of the dairy industry that is rich in lactose (approx. 70%), proteins (14%), and minerals (9%), represents a promising approach for microbial fermentation. With global whey production exceeding 200 million tons annually, the high biochemical oxygen demand underlines the important need for sustainable processing alternatives. This review explores the biotechnological potential of whey as a fermentation medium by examining its chemical composition, microbial interactions, and ability to support the synthesis of valuable metabolites. Functional microorganisms such as lactic acid bacteria (Lactobacillus helveticus, L. acidophilus), yeasts (Kluyveromyces marxianus), actinobacteria, and filamentous fungi (Aspergillus oryzae) have demonstrated the ability to efficiently convert whey into a wide range of bioactive compounds, including organic acids, exopolysaccharides (EPSs), bacteriocins, enzymes, and peptides. To enhance microbial growth and metabolite production, whey fermentation can be carried out using various techniques, including batch, fed-batch, continuous and immobilized cell fermentation, and membrane bioreactors. These bioprocessing methods improve substrate utilization and metabolite yields, contributing to the efficient utilization of whey. These bioactive compounds have diverse applications in food, pharmaceuticals, agriculture, and biofuels and strengthen the role of whey as a sustainable biotechnological resource. Patents and clinical studies confirm the diverse bioactivities of whey-derived metabolites and their industrial potential. Whey peptides provide antihypertensive, antioxidant, immunomodulatory, and antimicrobial benefits, while bacteriocins and EPSs act as natural preservatives in foods and pharmaceuticals. Also, organic acids such as lactic acid and propionic acid act as biopreservatives that improve food safety and provide health-promoting formulations. These results emphasize whey’s significant industrial relevance as a sustainable, cost-efficient substrate for the production of high-quality bioactive compounds in the food, pharmaceutical, agricultural, and bioenergy sectors.

The role of prebiotics and probiotics in promoting gut health is increasingly recognized in food development and nutrition research. This study explored the enhancement of probiotic viability in the food industry through microencapsulated synbiotics, focusing on Lactiplantibacillus plantarum NCIMB 11974 with fructooligosaccharides (FOSs) and inulin as prebiotics. The effect of encapsulation in a chitosan-coated alginate matrix on probiotic survival under simulated gastrointestinal conditions showed a significant effect of 2% FOS concentration on the growth of Lactiplantibacillus plantarum NCIMB 11974. The optimization of microencapsulation parameters by the Taguchi method revealed a 2% sodium alginate concentration, a nozzle size of 200 µm, and a concentration of 0.4% chitosan solution as ideal, producing microcapsules with an estimated average diameter of 212 µm. Viability assessments in simulated gastric juice and simulated intestinal juice showed that chitosan-coated alginate microcapsules notably enhanced probiotic survival, achieving log 8 CFU mL⁻¹ viability in both environments, a marked improvement over the uncoated variant. The study emphasizes the importance of microencapsulation, particularly by sodium alginate and chitosan, as a viable strategy to improve the survival and delivery of probiotics through the digestive system. By improving the stability and survivability of probiotics, microencapsulation promises to expand the use of synbiotics in various foods, contributing to the development of functional foods with health-promoting properties.

Interest in non-viable microbial preparations has increased as an alternative to selected technological and safety limitations of live probiotics. Paraprobiotics generally comprise non-viable intact or fragmented microbial cells, whereas the International Scientific Association for Probiotics and Prebiotics (ISAPP) definition of a postbiotic requires a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host. This review critically evaluates mechanisms, clinical evidence, food applications, manufacturing, regulation, and future research priorities. Non-viable microbial preparations can modulate host responses through cell-associated structures, including peptidoglycan, lipoteichoic acids, surface proteins, and exopolysaccharides (EPS), while microbial-derived metabolites such as short-chain fatty acids contribute to barrier and host–microbiota signaling; isolated metabolites, however, should not automatically be classified as postbiotics. Clinical evidence remains preparation- and indication-specific, with stronger evidence for selected preparations such as heat-inactivated Bifidobacterium bifidum MIMBb75 in irritable bowel syndrome (IBS) and more limited or predominantly preclinical evidence for other indications. In food systems, effects on stability, texture, microbial quality, sensory acceptance, and functionality depend on strain, processing, concentration, and matrix. Key barriers include inconsistent terminology, variable inactivation procedures, incomplete characterization, non-standardized dosing, limited long-term clinical evidence, and fragmented regulation. Progress will require reproducible manufacturing, verified residual non-viability, molecular characterization, potency markers, standardized dose reporting, and preparation-specific clinical validation.