Groundnut shells to bioethanol: comparative yeast performance and ethanol characterization

The effect of three different yeast species (Saccharomyces cerevisiae, Saccharomyces cariocanus, and Schizosaccharomyces pombe) on bioethanol production from groundnut shells was investigated at exactly same process conditions i.e temperature of 35 and five days fermentation period. The physicochemical properties of the generated bioethanol from the optimal yeast species (Saccharomyces cariocanus) was also evaluated. It was found that the descending sugar concentrations were similar across all the three species (72.76–74.35 mg/dL) with negligible variations. However, significant variations were observed in bioethanol quantity and percentage yield. Saccharomyces cariocanus generated the highest quantity of bioethanol (102 mL) and yield (34%), followed by saccharomyces cerevisiae (90 mL, 30%), with Schizosaccharomyces pombe having the lowest performance (73 mL, 24%). This reveals the superior fermentative efficiency of Saccharomyces cariocanus in converting sugars to ethanol. The physicochemical properties of bioethanol produced by Saccharomyces cariocanus were generally comparable to ASTM standards (indicating acceptable fuel quality) with slight deviations in density and boiling point which could be attributed to impurities. The study emphasizes the importance of yeast species selection in enhancing bioethanol production from groundnut shell feedstocks and identifies Saccharomyces cariocanus as a promising yeast for effective ethanol fermentation. It is concluded that groundnut shells are promising feedstock for bioethanol production but further process optimization is required to fully meet fuel standards.