The Effect of Type and Concentration Yeast with Fermentation Time and Liquifaction Variations on the Bioethanol Concentration Resulted by Sorgum Seeds with Hydrolysis and Fermentation Processes

Abstract

Sorghum is one of the plants that can be used as raw material for making bioethanol. Sorghum has seeds with a starch composition of 73.8%, which is potential as a raw material for making bioethanol. Sorghum starch can be converted into bioethanol through the hydrolysis process (the process of converting carbohydrates into glucose) which consists of liquefaction and saccharification processes and is followed by a fermentation process. The hydrolysis method is carried out enzymatically. In this study alpha amylase and gluco amylase enzymes were used with various types of yeast including Saccharomyces cerevisiae, Rhizopus oryzae, Acetobacter xylinum, Mucor sp, and Aspergilus niger which varied with liquefaction temperatures including 80, 85, 90, 95, and 100 °C. Obtained the most optimal yeast is Saccharomyces cerevisiae with an optimal temperature of 95 °C resulting in a bioethanol concentration of 4.3%. After getting the optimal yeast and temperature, the fermentation step of the two variables is used in the next step. In the fermentation process, variations of yeast concentration and duration of fermentation were used, the optimum yeast concentration was at 2.5% with 48 hours of fermentation resulting in bioethanol concentration of 11%.