Variation of Recidence Time With Yeast Type Affecting the Concentration of Bioethanol Based on Sorgum Seeds Through Hydrolysis and Fermentation Processes

One of the plants used as a producer of bioethanol is sorghum . Sorghum has seeds with a starch composition of 80.4 %, which is potential as a raw material for making bioethanol. Sorghum starch can be converted into bioethanol through a hydrolysis process (the process of converting carbohydrates into glucose) which consists of a liquefaction and saccharification process and followed by a fermentation process. The hydrolysis method is carried out enzymatically. This research used alpha amylase and gluco amylase enzymes with various types of yeast including Lactobacilus Casei, Rhizopus Oligosporus, Candida Glabrata, Saccharomyces Cerevisiae, and Neurospora Crassa which varied with liquefaction temperature covering 95 o C. After getting yeast which is optimal at that temperature , then the second fermentation stage of the variables used in the next phase. In the fermentation process, variations in percent yeast levels are used with variations of 1%, 1.5%, 2%, 2.5% and 3% . Obtained the most optimal yeast is Saccharomyces Cerevisiae with optimal yeast concentration at 2.5% with 48 hours of fermentation which results in a bioethanol concentration of 4.3% in the initial sugar concentration of 11,998 g / L. After analysis, the most optimal bioethanol product has physical properties, namely the density of 0.783 gr / mL with a refractive index of 1.3589