Bacillaceae in Probiotics and Postbiotics: Applications, Functional Traits, Mechanisms and Outlook.

Despite the well-documented health benefits of non-spore-forming probiotics such as Lactobacillus and Bifidobacterium, their broader application can be constrained by limited stability and survivability during processing, storage and gastrointestinal transit. These limitations have driven growing interest in spore-forming bacteria belonging to Bacillaceae family for potential use as probiotics particularly for products that require heat processing or extended shelf-life. This review focuses on the genera Bacillus, Heyndrickxia and Priestia, which have established roles across biotechnology, food and industrial applications, with evidence demonstrating benefits in plants, animals and human nutrition. Key technological traits, carbohydrates and nitrogen metabolism capacities and bioactive outputs are highlighted in this review, including the production of enzymes, antimicrobial compounds such as bacteriocins and non-ribosomal synthesized peptides, as well as other metabolites relevant to host and microbiome modulation. The mechanistic basis underpinning reported functions, such as competitive exclusions, antimicrobial activity, and immunomodulatory effect are also discussed in the context of probiotic and postbiotic. Finally, translational considerations, challenges and outlook in spore-forming probiotic and postbiotic biosolutions are addressed, including strain specific efficacy, safety evaluation and long-term use, and the practical requirements for robust human validation. This review intends to provide a critical and comprehensive synthesis, to update and further encourage researchers and industry stakeholders in developing Bacillaceae-based probiotics and postbiotics that align with the market needs.