VERY HIGH GRAVITY FERMENTATION WITH ERGOSTEROL AND TWEEN80 SUPPLEMENTATION: A NOVEL APPROACH IN BIOETHANOL PRODUCTION FROM NYPA FRUTICANS SAPFAJAR RESTUHADI AND EVY ROSSI
A vast population of nypa palm (Nypa fruticans) found in abundance in mangrove forests along the eastern coastline of Sumatera Island in Indonesia. It has been reported that nypa palm is capable of producing up to 15,600 L of ethanol per hectare, more than twice the yield of sugar cane, and six times the yield of corn. However, the natural muddy area of the nypa forest creates a major transportation problem to bring the nypa sap to the bioethanol plant on time. This can lead to unwanted contamination and degradation of the nypa sap quality (i.e. glucose concentration). The very high gravity (VHG) fermentation offers several advantages for industrial applications to increase in both the ethanol concentration and the rate of fermentation which reduce capital costs, energy costs per liter of alcohol and the risk of bacterial contamination. However, it may have a negative effect upon the yeast performance due to the elevated osmotic pressure and the production of high levels of ethanol. This study was conducted to determine the optimization of bioethanol production with free cells, to learn the effect of combined treatments of osmotic shocked depressant substances (Tween80 and Ergo sterol) in a high glucose concentration medium. This research was carried out in experiments with four ergo stereo levels: E0 (0 mg/L), E1 (18 mg/L), E2 (24 mg/ L) and E3 (30 mg/L) with 0.2 % w/v Tween80. It demonstrated after 5 days, the fermentation of VHG medium was capable to increase the ethanol concentration, but might have a negative effect upon the yeast performance due to the elevated osmotic pressure of the medium. Ergo sterol and Tween80 supplementation seemed successful to overcome the unwanted effect by lowering the surface tension and osmotic pressure of the medium. The best treatment is a combination of E1 (0.2% Twine 80 and ergo sterol 18 mg/L), which produces the highest ethanol concentration (17.57% v/v).
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