β-(1,3)/(1,6)-glucans derived from non-saccharomyces yeast cell walls with emphasis on structural components and biofunctional potential for food and health applications: A review

Although β-glucans from Saccharomyces cell walls have been extensively characterised, comparable structural and functional knowledge of β-(1,3)/(1,6)-glucans from non- Saccharomyces yeasts remains fragmented. This review therefore addresses that gap by consolidating recent findings on β-(1,3)- and β-(1,6)-glucans as the predominant structural polymers of non-Saccharomyces cell walls, which also feature an outer mannoprotein layer and are covalently interconnected with chitin, together with minor components such as inorganic polyphosphates. Coverage is restricted to genera for which experimental cell-wall composition and/or isolated β-glucan data are available, principally Candida, Kluyveromyces, Debaryomyces, Pichia / Komagataella, Yarrowia, Schizosaccharomyces, Cryptococcus, Aureobasidium, Metschnikowia, Hanseniaspora, Torulaspora, Rhodotorula and related ascomycetous and basidiomycetous yeasts. Alkali- and enzyme-based extraction protocols yield β-glucan–chitin complexes whose molecular weight, degree of branching and purity govern their technological and biological performance. These β-glucans exhibit antioxidant activity via hydrogen-atom donation from hydroxyl groups, adsorb mycotoxins through hydrogen bonding and hydrophobic interactions, and display antimicrobial effects driven by electrostatic interactions and immune modulation. They further possess immunostimulatory and antitumor activities, engaging pattern-recognition receptors (Dectin-1, CR3 and TLRs) to activate macrophages, natural killer (NK) cells and T-lymphocytes. Supplementation of growth media with β-glucan can enhance biocontrol efficacy against postharvest phytopathogens. The distinctive structural features and multifunctional properties of non- Saccharomyces β-(1,3)/(1,6)-glucans position them as candidate ingredients for food preservation, nutraceuticals, feed additives and sustainable biocontrol applications.