Screening of Microorganisms Capable of Producing Ethanol by Direct Fermentation of D-Xylose

摘要

A total of 120 D-xylose fermenting yeast strains were isolated from composition soil samples. 6 strains capable of fermenting D-xylose to produce ethanol were obtained by TTC double medium agar method screening and potassium dichromate oxidation method re-screening. All the 6 strains belong to the genera Candida or Pichia by morphology and physiology identification. Candida spp. strains showed rather high efficiency to produce ethanol from D-xylose than the Pichia spp. strains, of which, strain M-105 exhibited a D-xylose consumption rate of 98.28% and the highest ethanol yield (0.465 g/g), with concentration up to 18.58 g/L under the condition of fermenting 40'g/L of this sugar at 28°C and 100 r/min for 72 hours. An average ethanol concentration of 18.35±0.07 g/L was reached from three batches fermentation of M-105 in shaking flask.