Objective  An optimized low-cost medium for high-density culture of Saccharomyces cerevisiae was formulated.

  Method  S. cerevisiae JH301 was cultured on the basic molasses media of varied compositions to determine the optimal carbon source, nitrogen source, inorganic salt, and natural growth promoters for the yeast preparation in a single factor test. Optimization models using different statistical analyses were compared for the formulation finalization.

  Result  From a U₁₆(8⁸) uniform experiment, the optimized medium formulation was determined to apply the carbon source that included glucose, cottonseed sugar, and trehalose, tryptone for the nitrogen source, K₂HPO₄ as the inorganic salt, and the natural growth promoters that consisted of distiller's grains polypeptide, rice saccharification solution, and soybean polysaccharide. The finalized formula called for 23.72 g·L⁻¹ distiller's grains polypeptide, 44.15 g·L⁻¹ rice saccharification solution, 31.88 g·L⁻¹ soybean polysaccharide, 22.45 g·L⁻¹ cottonseed sugar, 13.97 g·L⁻¹ glucose, 15.00 g·L⁻¹ trehalose, 27.25 g·L⁻¹ tryptone, and 3.00 g·L⁻¹ K₂HPO_4, in addition to 10% soluble solids molasses. The resulting yeast biomass reached 1.48×10⁸ cfu·mL⁻¹, which was one order of magnitude higher than the culture obtained from the basic molasses medium.

  Conclusion  Rich in small molecular polypeptides capable of promoting the cell proliferation of S. cerevisiae, the natural distiller's grains polypeptide was formulated in the medium to yield a low-cost preparation for the yeast.