Fuel ethanol production using xylose assimilating and high ethanol producing thermosensitive Saccharomyces cerevisiae isolated from date palm juice in Bangladesh

Four yeasts were isolated from Khejurer Rosh [an overnight natural fermented date palm (Phoenix dactylifera) juice/sap] at low temperature (similar to 5-15 degrees C) to produce bioethanol. Cultural, morphological, physiological, biochemical and genetic analysis were carried out under various physiological conditions. All 4-strains (Dj-1, Dj-2, Dj-3, and Dj-4) could produce bioethanol and their production rates were further investigated under various carbon sources, growth temperatures, and pHs. Among them, the highest 10% (v/v) bioethanol was estimated from the thermosensitive yeast strain Dj-3, which was grown in the medium containing 18% of total sugars and 0.05% (NH4)(2)SO4 at optimum temperature and pH of 25 degrees C and 6.0, respectively. Microscopic study and a partial 26S rDNA (D1/D2 region) sequencing identified Dj-1, and Dj-3 as Saccharomyces cerevisiae, whereas, Dj-2 and Dj-4 strains were, Pichia kudriavzevii, and Debaryomyces hansenii, respectively. The strains Dj-3 and Dj-4 could grow well in the medium containing xylose as the sole carbon source. Our results conclude that the strain Dj-3 is a natural mutant strain of Saccharomyces cerevisiae, which would be an industrially potential candidate for bioethanol production.