Isoamyl alcohol and isobutanol production in sugarcane molasses fermentation in a microdistillery: pH, refrigeration, and supplementation effects

Abstract

Fusel oil, a blend of higher alcohols generated during fermentation, predominantly comprises isoamyl alcohol and isobutanol. Despite their adverse effects on distillation and ethanol quality, these alcohols find widespread use, notably in the fine chemical industry. Fusel oil quality and quantity vary due to multiple factors, including raw materials and fermentation conditions. This study aimed to investigate the effects of pH, refrigeration, and supplementation on isoamyl alcohol and isobutanol formation during molasses must fermentation in a microdistillery. The fermentations were conducted in batches that were fed with 25 °Brix must and 25% v/v commercial dry yeast for 10 hours. A complete 2³ factorial design was used to assess the effects of the studied factors and their interactions on the response variables: fermentation efficiency (n_f), process efficiency (n_p), ethanol productivity (P), substrate-to-cell conversion factor (Y_X/S), isoamyl alcohol produced (A), isobutanol produced (B) and the A/B Ratio between these alcohols. Statistical analysis employed ANOVA and Tukey’s test. The results of the substrate-to-cell conversion factor (Y_X/S) indicated good yeast performance under different fermentation conditions. The interaction effects among the evaluated factors significantly influenced the formation of isoamyl alcohol and isobutanol, as well as the A/B Ratio.