Production of Bioethanol from Sweet Sorghum [Sorghum Bicolor L.] Juice Using Yeast Isolated from Fermented Sweet Sorghum Juice

Abstract

Background Nonrenewable energies have been used as the major sources of energy in the world so far. However, they are not sustainable and environmentally friendly and there is an urgent need to search for alternative renewable sustainable energy sources. Sweet sorghum is a sugar rich plant that can be used as an important alternative source of bioenergy that is renewable with a low contribution to global warming without computing food security. This study aimed to investigate the potential of sweet sorghum juice for bioethanol production using yeast isolated from fermented sweet sorghum juice. Methods Sweet sorghum juice oBrix was determined using a digital refractometer.Yeasts isolated from fermented sweet sorghum juice were characterized using different biochemical tests. Potent yeast was used in the fermentation of sweet sorghum juice which was carried out at different fermentation parameters, mainly pH, temperature, and incubation period, using a completely randomized factorial design. Ethanol content was determined using a potassium dichromate solution. Results About 18 of yeast isolates were selected based on the sugar fermentation test for further characterization. The morphology and biochemical tests of the yeasts carried out suggest that all the yeast isolates have belonged to the genus Saccharomyces. The most ethanol tolerant yeast isolate, SJU14, was used for fermentation. ANOVA showed that, maximum ethanol content (18.765%) was produced at 30/26 oC, pH of 4.5, incubated for 96 hrs. Conclusion Sweet sorghum juice found excellent source of potent yeasts and these yeasts have important industrial property such as able to grow at high ethanol and glucose concentration. Sweet sorghum juice can be used as an alternative substrate for bioethanol production to minimize the environmental threat caused by fossil fuels. Further research is recommended to strategically develop value-added utilization of sweet sorghum vis-à-vis improving food system and mitigating climate change.