Pichia Kudriavzevii as an Emerging Probiotic Yeast for Sustainable Animal Nutrition: Functional Mechanisms, Safety Challenges, and Perspectives from Established Saccharomyces Cerevisiae Var. Boulardii.

Yeast-based probiotics have gained increasing attention as alternatives to bacterial probiotics due to their resilience under gastrointestinal stress conditions, compatibility with antimicrobial environments, and ability to produce biologically active metabolites. Among probiotic yeasts, Saccharomyces cerevisiae var. boulardii represents the most established and clinically validated probiotic yeast, whereas Pichia kudriavzevii has emerged as a promising but still under-investigated candidate for animal nutrition applications. This review critically evaluates the functional potential of P. kudriavzevii by examining its gastrointestinal adaptability, antimicrobial activity, enzymatic capabilities, immunomodulatory effects, mycotoxin mitigation potential, and applications across poultry, swine, ruminant, and aquaculture systems. Comparative insights with S. cerevisiae var. boulardii highlight differences in probiotic mechanisms, functional advantages, and limitations. Although P. kudriavzevii demonstrates considerable stress tolerance and diverse metabolic capabilities, current evidence remains largely dependent on individual strains and experimental models, with many reported probiotic properties originating from in vitro investigations or limited animal studies. Its application requires careful strain-level characterization due to biosafety concerns, regulatory limitations, and the need for comprehensive genomic and toxicological assessment. Therefore, P. kudriavzevii should be considered a potential next-generation probiotic yeast rather than a replacement for established probiotic strains. This review provides a framework for future research aimed at validating the safety, efficacy, and practical implementation of emerging yeast probiotics in sustainable animal production.