Application of unconventional microorganisms for the production of non-alcoholic beer.

Non-alcoholic beer (NAB) is one of the rapidly expanding segments of the beer market, yet many products still suffer from wort-like sweetness, thin body, and muted hop-yeast complexity. These quality gaps arise because conventional approaches, such as limited fermentation with Saccharomyces or physical dealcoholization of regular beer, are fundamentally constrained by the central role of maltose and maltotriose fermentation in standard brewing. Unconventional microorganisms offer an alternative biological route to the production of NAB. Non-Saccharomyces and maltose-negative yeasts, lactic acid bacteria, mixed cultures and engineered strains combine restricted utilization of wort sugars with diverse metabolic outputs, including fruity and spicy aroma compounds, organic acids, glycerol and exopolysaccharides that can modulate flavor balance, mouthfeel and pH in the near absence of ethanol. Drawing on recently published pilot-scale and industrial examples, this review synthesizes current knowledge on how these organisms reshape wort sugar metabolism and the resulting volatile and non-volatile profiles in NAB. Particular attention is paid to realistic process concepts such as primary fermentation with maltose-negative yeasts, LAB-assisted fermentations, and restricted-ethanol fermentations using selected or engineered Saccharomyces variants. Remaining challenges include robustness in hopped wort, control of off-flavors (diacetyl, ethyl acetate, phenolic notes), regulatory acceptance of engineered strains and consistent sensory quality at scale. Overall, unconventional microorganisms emerge as key tools to close the sensory gap between NAB and regular beer while supporting more diverse, lower-impact brewing practices.