ETHANOL FERMENTATION FROM MICROWAVE-ASSISTED ACID PRETREATED RAW MATERIALS BY Scheffersomyces stipitis

Abstract

The production of value-added products from renewable resources have been studied by researchers for years and are still being studied due to the fact that there is a point of interest. In this study, ethanol production from microwave assisted acid pretreated renewable resources including barley husk, wheat bran, and rye bran was performed. The hydrolysis of renewable resources were performed at 700 W of microwave power, 6.92 min of irradiation time, 1:18.26 w/v of solid-to-liquid ratio, and 3.67% v/v of acid ratio for barley husk, 600 W, 6.92 min, 1:16.69 w/v, and 1.85% for wheat bran, and 460 W, 6.15 min, 1:17.14 w/v, and 2.72% for rye bran. The hydrolysates were detoxified with 2% (w/v) activated charcoal at 30ºC and 150 rpm for 30 min. Then, the enriched hydrolysates were utilized to produce ethanol in shake flask fermentation by Scheffersomyces stipitis (ATCC 58784) that is a xylose fermenting yeast at 150 rpm and 30ºC with 5% (v/v) inoculum size. Results indicated that the highest ethanol production (6.15 g/L) was performed in shake flask fermentation with wheat bran medium. However, the lowest ethanol concentration (1.37 g/L) was obtained from barley husk medium. Also, 4.89 g/L of ethanol was produced in rye bran media. Nonetheless, while the highest ethanol yield was calculated to be 44.11% in wheat bran media, the lowest ethanol yield was 12.78% in barley husk medium. On the other hand, the sugar utilization yields in barley husk, wheat bran, and rye bran mediums were also computed to be 85.33, 94.09, and 94.74%, respectively. Consequently, raw materials used in this study can be utilized as good carbon sources for production of ethanol by fermentation.