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 ᴅ-xylonate production without xylitol generation. The recombinant strain P. kudriavzevii N-X/S1 was employed for sequential production of ᴅ-xylonate and ethanol from ᴅ-xylose, feeding on ᴅ-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 ᴅ-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 ᴅ-xylonate and 20.8 g/L ethanol were produced at yields of 1.10 g/g ᴅ-xylose and 84.3% of theoretical value, respectively. We propose a promising approach for the sequential production of ᴅ-xylonate and ethanol from non-detoxified corncob using a single microorganism.
Highlights
Lignocellulosic biomass is a promising feedstock for the production of second-generation ethanol and biochemicals owing to its ready availability, economic efficiency and sustainability
We firstly evaluated the capacity of P. kudriavzevii N-X for ethanol production under various conditions in flasks
P. kudriavzevii was reported to have high osmotolerance, tolerating up to 48% (w/v) D-glucose, but the ethanol productivity is usually affected under high D-glucose concentrations [9,22,23]
Summary
Lignocellulosic biomass is a promising feedstock for the production of second-generation ethanol and biochemicals owing to its ready availability, economic efficiency and sustainability. D-xylose, the second most abundant sugar in lignocellulosic biomass, cannot be naturally utilized by S. cerevisiae. To improve the economic viability of the lignocellulosic ethanol industry, numerous genetic modifications have been performed to improve the xylose fermentation of S. cerevisiae in recent years [1]. In addition to converting D-xylose into ethanol, an alternative way to improve the lignocellulose-based bioeconomy is to convert D-xylose into other value-added chemicals [2]. An unconventional yeast Pichia kudriavzevii was considered to be an excellent production organism for D-xylonate, with advantages over S. cerevisiae due to its remarkable tolerance towards D-xylonate, low pH stress and lignocellulosic inhibitors [7,8]. P. kudriavzevii showed a higher capacity for ethanol production from non-detoxified lignocelluosic biomass than S. cerevisiae [9,10], making it a potential candidate host for improving the lignocellulosic-based bioeconomy
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