From physiology to food applications: Kluyveromyces marxianus as a key player for innovation in probiotic attributes, fermented foods and functional food ingredients.

Kluyveromyces marxianus is a non-conventional yeast of growing interest in food biotechnology due to rapid growth, thermotolerance, broad substrate use, and metabolic versatility. Current knowledge remains fragmented across genomics, physiology, probiotic traits, metabolite production, and food applications. This review summarizes recent advances in K. marxianus with a focus on its food applications and strain-level variability, highlighting how ecological origin, genomic background, ploidy, lactose-utilization systems, fructan-hydrolyzing capacity, stress responses, and genome-scale metabolic modeling are associated with differences in strain performance in food matrices. Quantitative comparisons with major food yeasts contextualize growth, thermotolerance, aroma, biomass, and fructan degradation. Selected strains have been evaluated in dairy, plant-based, alcoholic, cereal, and low-FODMAP products, and for functional ingredients such as fructooligosaccharides, single-cell protein, mannans, mannoproteins, and recombinant proteins. Probiotic traits are discussed cautiously, as benefits remain strain-specific and largely supported by in vitro or preclinical studies. For probiotic applications, strain-level safety, opportunistic infection risk, regulatory considerations, and validation in vulnerable populations require attention. Overall, food applications of K. marxianus should be guided by strain-level characterization, genotype-phenotype links, matrix-specific validation, and evidence-based safety assessment.