Yeast adaptation on softwood prehydrolysate

Area of Science:

• Biotechnology and Bioengineering
• Microbial Fermentation
• Renewable Energy

Background:

• Softwood prehydrolysate from forest underbrush is a potential feedstock for biofuel production.
• Hemicellulose, particularly hexosan, is the primary sugar component in selected western US softwoods like Douglas fir.
• Yeast fermentation is crucial for converting sugars into biofuels such as ethanol.

Purpose of the Study:

• To screen and select yeast strains capable of growing on dilute acid-pretreated softwood prehydrolysate.
• To adapt selected yeast isolates for improved tolerance and growth in the presence of prehydrolysate and ethanol.
• To evaluate the performance of adapted yeast strains in simultaneous saccharification and fermentation (SSF) processes.

Main Methods:

• Screening of multiple yeast strains including Saccharomyces cerevisiae, Pachysolen tannophilus, Brettanomyces custersii, Candida shehatae, and Candida acidothermophilum.
• Selection and adaptation of superior yeast isolates through serial batch cultures with increasing prehydrolysate concentrations.
• Evaluation of microaerophilic conditions to enhance tolerance to hydrolysate and ethanol.
• Comparison of adapted strains against wild-type strains in simultaneous saccharification and fermentation (SSF).

Main Results:

• Several yeast strains demonstrated growth on softwood prehydrolysate, with two isolates showing superior initial performance.
• Adaptation significantly improved yeast growth and tolerance to increasing concentrations of prehydrolysate and ethanol.
• Adapted yeast strains exhibited enhanced performance in SSF compared to their wild-type counterparts, indicating greater efficiency in sugar conversion.

Conclusions:

• Yeast adaptation is a viable strategy to enhance microbial performance on lignocellulosic feedstocks like softwood prehydrolysate.
• Adapted yeast strains show promise for efficient and cost-effective biofuel production from underutilized forest resources.
• This research contributes to the development of sustainable fermentation processes for the biorefinery industry.