Probiotic soy yogurt: a review of microbial metabolism, strain selection, and biotechnological advances in plant-based fermentation

The growing demand for plant-based functional foods has positioned soy yogurt as a promising alternative to dairy products. This review provides a critical, microbiology-focused examination of functional probiotic soy yogurt, covering the period from 2016 to 2026. Unlike previous broad nutritional surveys, this work uniquely synthesizes the microbiological determinants of fermentation, including strain selection criteria for Lactiplantibacillus spp., Streptococcus thermophilus , Bifidobacterium spp., and Saccharomyces boulardii . It also examines synergistic and competitive interactions in mixed cultures, alongside the optimization of fermentation parameters such as inoculum size and acidification kinetics. Particular emphasis is placed on the microbial conversion of isoflavone glycosides to bioactive aglycones via β-glucosidase activity, a process that significantly enhances functional properties. Biotechnological challenges, including post-acidification, probiotic viability during storage, and stabilization strategies such as microencapsulation, are critically evaluated. By synthesizing current knowledge on fermentation microbiology and strain functionality, this review highlights the scientific and technological considerations necessary for developing high-quality, commercially viable probiotic soy yogurt products with validated health claims.