Spent sulphite liquor utilization by xylose-assimilating yeast pachysolen tannophilus, capable of bioethanol producing

Abstract

The xylose-assimilating capacity of yeast Pachysolen tannophilus to utilize sugars in spent sulphite liquor samples (pulp mill waste) with a different concentration of hexoses and pentoses was studied. The consumption of hexoses (D-glucose, D-mannose, D-galactose) and pentose (D-xylose) in such substrates reached 90.0-97.5% and 49.12-67.45%, respectively. The ethanol production from sugars in spent sulphite liquor by different strains of the yeast P. tannophilus was demonstrated. The maximum specific rate and ethanol yield reached 9.32-11.45 g l-1 and 0.28-0.37 g g sugars-1, respectively. Thus, the principle possibility of using xylose-assimilating P. tannophilus yeast to obtain bioethanol from sulfite liquor with a different ratio of hexoses and pentoses was proved. According to theoretical calculations, this method will provide up to 42.6 liters of ethanol from 100 kg of sulfite liquor containing 55.6% D-xylose, 24.7% D-glucose, 8.7% D-mannose, 7.6% D-galactose, 3.7% L-arabinose. A future-oriented perspective on bioethanol production from pulp and paper industry wastes by the yeast P. tannophilus is considered.