ENHANCEMENT IN BIOETHANOL PRODUCTION USING ASPERGILLUS NIGER AND SACCHAROMYCES CEREVISIAE BY NITROGEN ADDITION ON MOLASSES FERMENTATION

摘要

Molasses as a by-product of the sugar industry have not been widely used to increase its economic value. Whereas molasses still contain 40-50% sucrose that can be utilized as raw material to produce bioethanol. There are two fermentation processes could be used: Separate Hydrolysis and Fermentation (SHF) and Simultaneous Saccharification and Fermentation (SSF). The purpose of this study was to compare SHF and SSF method to produce bioethanol with and without nitrogen addition. Experiments were conducted in a 2-L batch reactor. Molasses (333 g) which has been precipitated and sterilized at 120 °C for 30 minutes was poured into the reactor; distilled water was then added to make up one liter solution. Experiments were conducted with and without the addition of 2 g/L (NH4)2S04 as the nitrogen source. The hydrolysis of molasses was carried out by using Aspergillus niger 19.5 g/L, while the fermentation process used Saccharomyces cerevisiae at 8% (v/v). In SHF method, nitrogen was added after hydrolysis process, while in the SSF method nitrogen applied from the begiruiing of the process. The measurement of glucose and bioethanol concentration were performed every 24 hours during the experiments period of 96 hours. This study showed that molasses can be used as a raw material to produce bioethanol. The highest bioethanol result was 11.97% (v/v) for SSF method and 9.29% (v/v) for SHF method. These results were achieved when fermentation time was 48 hours. After 48 hours the alcohol content decreased because it is used by microorganisms for energy source and form acid. The SSF method with the addition of nitrogen produced bioethanol two times higher than SHF method. The addition of nitrogen affected the activity and survival of microorganism to increase the formation of glucose, which then convert to bioethanol.