Production of fuel ethanol at high temperature from sugar cane juice by a newly isolated Kluyveromyces marxianus

Kluyveromyces marxianus DMKU 3-1042, isolated by an enrichment technique in a sugar cane juice medium supplemented with 4% (w/v) ethanol at 35 °C, produced high concentrations of ethanol at both 40 and 45 °C. Ethanol production by this strain in shaking flask cultivation in sugar cane juice media at 37 °C was highest in a medium containing 22% total sugars, 0.05% (NH4)2SO4, 0.05% KH2PO4, and 0.15% MgSO4 · 7H2O and having a pH of 5.0; the ethanol concentration reached 8.7% (w/v), productivity 1.45 g/l/h and yield 77.5% of theoretical yield. At 40 °C, a maximal ethanol concentration of 6.78% (w/v), a productivity of 1.13 and a yield 60.4% of theoretical yield were obtained from the same medium, except that the pH was adjusted to 5.5. In a study on ethanol production in a 5 l jar fermenter with an agitation speed of 300 rpm and an aeration rate of 0.2 vvm throughout the fermentation, K. marxianus DMKU 3-1042 yielded a final ethanol concentration of 6.43% (w/v), a productivity of 1.3 g/l/h and a yield of 57.1% of theoretical yield.