Optimization of the simultaneous saccharification and fermentation process using thermotolerant yeasts

Area of Science:

• Biotechnology
• Microbiology
• Bioenergy

Background:

• Cellulosic materials are a sustainable feedstock for bioethanol production.
• High temperatures during simultaneous saccharification and fermentation (SSF) can inhibit yeast performance.
• Improving yeast thermotolerance is crucial for efficient cellulosic ethanol processes.

Purpose of the Study:

• To identify and develop thermotolerant yeast strains for enhanced SSF of cellulosic materials.
• To optimize fermentation conditions for improved ethanol yield at elevated temperatures.

Main Methods:

• Screening of Saccharomyces and Kluyveromyces yeasts for growth and fermentation at 42-47°C.
• Selection of K. marxianus LG as the most promising strain.
• Induction of thermotolerant clones from K. marxianus LG through various treatments.
• Evaluation of new clones in SSF of a 10% Solka-floc substrate at 45°C.

Main Results:

• K. marxianus LG demonstrated superior performance compared to other tested yeasts at higher temperatures.
• 35 novel thermotolerant K. marxianus LG clones were successfully generated.
• These clones significantly enhanced SSF efficiency at 45°C compared to the parent strain.
• Some clones achieved ethanol concentrations as high as 33 g/L.

Conclusions:

• Targeted treatments can effectively enhance yeast thermotolerance for SSF processes.
• Developed K. marxianus LG clones offer a promising solution for high-temperature cellulosic ethanol production.
• The improved strains have the potential to increase the economic viability of lignocellulosic biorefineries.