Enhancing ethanol production from cellulosic sugars using Scheffersomyces (Pichia) stipitis

Abstract

Studies were performed on the effect of CaCO₃ and CaCl₂ supplementation to fermentation medium for ethanol production from xylose, glucose, or their mixtures using Scheffersomyces (Pichia) stipitis. Both of these chemicals were found to improve maximum ethanol concentration and ethanol productivity. Use of xylose alone resulted in the production of 20.68 ± 0.44 g L⁻¹ ethanol with a productivity of 0.17 ± 0.00 g L⁻¹ h⁻¹, while xylose plus 3 g L⁻¹ CaCO₃ resulted in the production of 24.68 ± 0.75 g L⁻¹ ethanol with a productivity of 0.21 ± 0.01 g L⁻¹ h⁻¹. Use of xylose plus glucose in combination with 3 g L⁻¹ CaCO₃ resulted in the production of 47.37 ± 0.55 g L⁻¹ ethanol (aerobic culture), thus resulting in an ethanol productivity of 0.39 ± 0.00 g L⁻¹ h⁻¹. These values are 229 % of that achieved in xylose medium. Supplementation of xylose and glucose medium with 0.40 g L⁻¹ CaCl₂ resulted in the production of 44.84 ± 0.28 g L⁻¹ ethanol with a productivity of 0.37 ± 0.02 g L⁻¹ h⁻¹. Use of glucose plus 3 g L⁻¹ CaCO₃ resulted in the production of 57.39 ± 1.41 g L⁻¹ ethanol under micro-aerophilic conditions. These results indicate that supplementation of cellulosic sugars in the fermentation medium with CaCO₃ and CaCl₂ would improve economics of ethanol production from agricultural residues.