Optimization of Process Variables for Bioethanol Production using Saccharomyces Cerevisiae

This study explores the production and optimization of bioethanol from palm wine via enzymatic fermentation using Saccharomyces cerevisiae. Palm wine, rich in fermentable sugars, served as a low-cost renewable feedstock. Fermentation was facilitated by yeast enzymes (invertase and zymase), which hydrolyzed sucrose into glucose and fructose, subsequently converted to ethanol and carbon dioxide. The effects of yeast dosage, fermentation temperature, and time on ethanol yield and concentration were systematically investigated through 20 experimental runs, with ethanol quantified by acid dichromate oxidation and titrimetric back titration. Ethanol concentrations ranged from 1.47 to 6.80 mol/L, with yields between 8.61% and 39.56%. Optimal conditions 3.24% yeast, 51.15°C, and 55 minutes produced the highest yields. Physicochemical analysis (specific gravity, viscosity, flash point, refractive index, cloud point, and pour point) confirmed ethanol quality, though slight deviations indicated minor impurities such as water, glycerol, or residual sugars. FTIR spectroscopy verified ethanol identity, with characteristic O–H, C–H, and C–O peaks, while minor signals suggested traces of by-products. Optimization using Response Surface Methodology (RSM) with a Central Composite Design (CCD) demonstrated excellent predictive accuracy (R² = 0.9973, Adjusted R² = 0.9949, Predicted R² = 0.9683). The model predicted a maximum yield of 40.81% v/v, closely matching experimental validation (40.03% v/v, 1.91% deviation). These findings confirm palm wine as a promising substrate for efficient bioethanol production, offering a sustainable, locally adaptable pathway for renewable energy development.