초록
Bioethanol has been considered as one of the alternative energy resources for fossil fuel substitute. Second generation of bioethanol production usually uses lignocellulosic material as its raw material which conducted at high temperature range (70-80<SUP>o</SUP>C). In this case the thermophilic microbe is needed for fermentation process in order to minimize the use of energy. This paper will discuss the results of the study on bioethanol production from glucose by using thermophilic microbes isolated from local source namely from Ciater hot springs in Subang District, Indonesia. In this study six thermophilic isolates (C1, C2, C3, C4, C5 and C6) were tested their capability in producing ethanol in the fermentation medium containing 5% glucose substrate for 5 days incubation. To determine the activity of isolates in ferment substrate is done by measuring the concentration of glucose and ethanol produced using a spectrophotometer. Isolates tested (C1,C2,C3,C4 and C5) could reduce glucose concentration from 1.1up to 1.7% in the fermentation medium. The ethanol produced was tested qualitatively by reacting the samples with K<SUB>2</SUB>Cr<SUB>2</SUB>O<SUB>7</SUB>inacidic conditions by observing its color change from yellow-orange to green-blue. The presence of ethanol indicatedby the decrease of OD's sample. This study showed that all isolates have the ability to produce ethanol. However, there are 2 isolates potentially produce ethanol that isolates C3 and C5 are characterized by low absorbance after adding potassium dichromate (K<SUB>2</SUB>Cr<SUB>2</SUB>O<SUB>7</SUB>).