Isolation and characterization of two soil derived yeasts for bioethanol production on Cassava starch

Two ethanol-producing yeast strains, CHY1011 and CHFY0901 were isolated from soil in South Korea using an enrichment technique in a yeast peptone dextrose medium supplemented with 5% (w v(-1)) ethanol at 30 degrees C. The phenotypic and physiological characteristics, as well as molecular phylogenetic analysis based on the D1/D2 domains of the large subunit (26S) rRNA gene and the internally transcribed spacer (ITS) 1 + 2 regions suggested that they were novel strains of Saccharomyces cerevisiae. During shaking flask cultivation, the highest ethanol productivity and theoretical yield of S. cerevisiae CHY1011 in YPD media containing 9.5% total sugars was 1.06 +/- 0.02 gl(-1)h(-1) and 95.5 +/- 1.2%, respectively, while those for S. cerevisiae CHFY0901 were 0.97 +/- 0.03 gl(-1) h(-1) and 91.8 +/- 12.2%, respectively. Simultaneous saccharification and fermentation for ethanol production was carried out using liquefied cassava (Manihot esculenta) starch in a 51 lab-scale jar fermenter at 32 degrees C for 66 h with an agitation speed of 2 Hz. Under these conditions, S. cereuisiae CHY1011 and CHFY0901 yielded a final ethanol concentration of 89.1 +/- 0.87 gl(-1) and 83.8 +/- 1.11 gl(-1), a maximum ethanol productivity of 2.10 +/- 0.02 gl(-1)h(-1) and 1.88 +/- 0.01 gl(-1)h(-1), and a theoretical yield of 93.5 +/- 1.4% and 91.3 +/- 1.1%, respectively. These results suggest that S. cerevisiae CHY1011 and CHFY0901 have potential use in industrial bioethanol fermentation processes. (C) 2010 Elsevier Ltd. All rights reserved.