Optimizing Bioethanol Production from Elephant grass (Pennisetum purpureum) Using Lime-Buffered Fermentation and Gompertz Kinetic Modeling

This study investigates the use of lime as a buffer solution to optimize pH and temperature for the fermentation of bioethanol from elephant grass (Pennisetum purpureum), a non-edible biomass. Bioethanol is an environmentally friendly alternative to fossil fuels, produced through the fermentation of starches, sugars, or cellulose. This study emphasizes the importance of controlling pH and temperature during fermentation, noting that enzymatic hydrolysis typically requires higher temperatures than fermentation. Samples of elephant grass were incubated at different pH levels (۴.۰, ۴.۵, ۵.۰, ۵.۵, and ۶.۰) and temperatures (۲۵, ۳۵, and ۴۰ ℃) for one week. Following acid hydrolysis using lime—which also serves as a mildly acidic substance—as the nutrient medium, fermentation was conducted using baker’s yeast, selected for its cost-effectiveness and wide availability. The ethanol yields were measured and recorded using a digital refractometer. The results were analyzed using the Gompertz method to verify the accuracy of the experimental findings. The results showed that lime not only increased ethanol production efficiency but also affected the enzymes by maximizing yeast growth at temperatures above ۳۰ ℃, specifically ۳۵ ℃ in this study, with a total yield of ۸ % (v/v) ethanol concentration and ۱۲ % (v/v) ethanol concentration on the peak day (day ۳) at a pH of ۴. These findings indicate that temperature enhances ethanol concentration, whereas higher pH levels inhibit it.