Yeast postbiotics: Opportunities and challenges in applications as functional biogenics for human nutrition

Probiotics are widely used in the food and nutraceutical industries; however, their application can be constrained by stability issues and safety concerns in vulnerable populations. Postbiotics, comprising inanimate probiotic microorganisms and/or their components and metabolites, confer health benefits on the host. They are regarded as potentially safer and more stable than probiotics and have a longer shelf life. This review aims to critically examine current advances in the identification of unexplored yeast postbiotics from Saccharomyces and non-Saccharomyces species, their production strategies through fermentation, metabolite profiling and screening approaches, functional mechanisms, and applications in nutraceuticals and functional foods. This review is intended to provide insights for scientists, biotechnologists, and food-industry professionals into the emerging field of "NextGen Biotics". The potential of underutilised Saccharomyces and non-Saccharomyces probiotic yeasts and their diverse array of metabolites, which hold promise for industrial applications, is discussed. The production strategies examined herein emphasise the need to optimise fermentation conditions to improve metabolite production. The integration of advanced analytical and bioprospecting approaches for characterisation is pivotal. The multifaceted benefits and technical advantages of yeast postbiotics position them as viable candidates to meet the increasing demand for preventive healthcare solutions and functional-food ingredients. The insights from this review reinforce the incorporation of yeast postbiotics into nutritional strategies for sustainable, safe, and effective health interventions. Addressing current scientific, technological, and regulatory gaps will be essential to improve their reproducibility, industrial applicability, and commercial translation.