Optimization of yeast inoculum and wort density for alcohol production from red sorghum wort

The optimization of fermentation conditions is essential for improving ethanol production and process efficiency in sorghum-based brewing systems. This study investigated the combined effects of wort density and yeast inoculum size on ethanol production, fermentation performance, and yeast growth during red sorghum wort fermentation by Saccharomyces cerevisiae . A 3 × 3 factorial design was applied using three wort densities (14, 16, and 18°P) and three inoculum levels (10 5 , 10 6 , and 10 7 CFU/mL). Response Surface Methodology (RSM) was used to model alcohol production and identify optimal fermentation conditions. Alcohol production ranged from 5.2 to 7.7% (v/v), with the highest experimental value obtained at 16°P and 10 6 CFU/mL. Analysis of variance revealed significant linear, quadratic, and interaction effects of wort density and inoculum size on ethanol production ( p < 0.01), and the fitted quadratic model explained 87.9% of the total variability. Desirability analysis predicted a maximum alcohol content of 8.0% (v/v) at 18°P and 10 6 CFU/mL. Yeast viability and cell concentration increased with wort density and inoculum size, reaching their highest values at 18°P and 10 7 CFU/mL, whereas the highest experimental alcohol concentration was obtained at 16°P and 10 6 CFU/mL. These results indicate that final yeast abundance and viability alone did not account for the differences in alcohol production among treatments.