Sequential production of D-xylonate and ethanol from non-detoxified corncob at low-ph by Pichia Kudriavzevii via a two-stage fermentation strategy

Abstract

Improving the comprehensive utilization of sugars in lignocellulosic biomass is a major challenge for enhancing the economic viability of lignocellulose biorefinement. A robust yeast Pichia kudriavzevii N-X showed excellent performance in ethanol production under high temperature and low pH conditions and was engineered for D-xylonate production without xylitol generation. The recombinant strain P. kudriavzevii N-X/S1 was employed for sequential production of D-xylonate and ethanol from D-xylose, feeding on D-glucose without pH control in a two-stage strategy of aerobic and shifting micro-aerobic fermentation. Acid-pretreated corncob without detoxification and filtration was used for D-xylonate production, then simultaneous saccharification and ethanol fermentation was performed with cellulase added at pH 4.0 and at 40◦C. By this strategy, 33.5 g/L D-xylonate and 20.8 g/L ethanol were produced at yields of 1.10 g/g D-xylose and 84.3% of theoretical value, respectively. We propose a promising approach for the sequential production of D-xylonate and ethanol from non-detoxified corncob using a single microorganism.