The production of craft beer depends on the quality and availability of yeast. However, many small breweries in developing countries face high costs due to their reliance on imported yeast strains. Developing efficient and low-cost propagation methods is therefore essential for sustainable production. A lager-type Saccharomyces cerevisiae strain (SC-Lager2) was propagated using both synthetic and low-cost alternative media. The latter was formulated with malt extract as a carbon source and yeast extract obtained from brewery by-products as a nitrogen source. A Plackett–Burman design identified significant factors influencing growth (p < 0.05), and a full factorial design (2⁴) optimized conditions. Growth kinetics and biomass yield were validated at laboratory (2 L) and pilot (83 L) scales. Maltose, yeast extract, zinc sulfate, and agitation significantly affected cell density and viability (p < 0.05). Under optimized conditions, 100% viability, a maximum cell density of 1.4 × 10¹⁰ cells/mL, and a biomass yield of 10 g/L were achieved values that were statistically higher (p < 0.05) than those obtained with the synthetic medium. The maximum specific growth rate (μ_max) increased by 52%, while doubling time decreased by 39%. Overall, the use of agro-industrial by-products reduced medium costs by approximately 65% compared to conventional synthetic formulations. The proposed low-cost medium provides a scalable, economical, and sustainable solution for yeast propagation, reducing production costs while maintaining high cell viability and performance. This approach supports the autonomy and competitiveness of the craft beer sector in developing regions.