Novel two-stage fermentation process for bioethanol production using Saccharomyces pastorianus

Area of Science:

• Biotechnology
• Bioenergy
• Microbial Fermentation

Background:

• Economic bioethanol production from lignocellulosic biomass requires efficient conversion of both glucose and xylose.
• Saccharomyces yeasts efficiently ferment glucose but struggle with xylose due to lacking metabolic pathways.
• Developing alternative fermentation strategies is crucial for improving bioethanol yields.

Purpose of the Study:

• To investigate a novel two-stage fermentation process to enhance bioethanol productivity.
• To evaluate the efficacy of Escherichia coli extract and xylose isomerase in improving xylose conversion.
• To compare the performance of the novel process with traditional Saccharomyces fermentations.

Main Methods:

• A two-stage fermentation process utilizing a non-Saccharomyces microorganism (Escherichia coli) for xylose conversion to biomass.
• Preparation of Escherichia coli extract for supplementation.
• Addition of Escherichia coli extract and/or xylose isomerase to Saccharomyces pastorianus fermentations using pure sugars and corn stover hydrolysates.

Main Results:

• Escherichia coli efficiently converted xylose to biomass.
• Escherichia coli extract addition significantly increased ethanol productivities on both pure sugars and corn stover hydrolysates.
• Xylose isomerase addition improved ethanol productivity on pure sugars but was less effective on hydrolysates alone.
• Ethanol productivities on corn stover hydrolysates with E. coli extract matched those on pure sugars with both additives.

Conclusions:

• The novel two-stage fermentation process demonstrates potential for competitive bioethanol production.
• Escherichia coli extract is a key component for improving xylose utilization in lignocellulosic bioethanol fermentation.
• This approach offers a viable alternative to recombinant Saccharomyces cerevisiae-based fermentations.