Evolutionarily engineered ethanologenic yeast detoxifies lignocellulosic biomass conversion inhibitors by...

Area of Science:

• Biotechnology
• Microbial Physiology
• Metabolic Engineering

Background:

• Furfural and 5-hydroxymethylfurfural (HMF) are key inhibitors in lignocellulosic biomass conversion, hindering microbial growth and ethanol fermentation.
• Understanding yeast tolerance and detoxification mechanisms is crucial for advancing sustainable cellulosic ethanol production.
• Previous studies identified yeast genes linked to inhibitor tolerance, but detailed mechanisms remain largely unknown.

Purpose of the Study:

• To investigate the pathway-based transcription profiles associated with yeast tolerance and detoxification of furfural and HMF.
• To elucidate the mechanisms underlying the tolerance and detoxification capabilities of a robust ethanologenic yeast strain, Saccharomyces cerevisiae NRRL Y-50049.

Main Methods:

• Utilized absolute mRNA quantification assays to analyze transcription profiles.
• Employed a tolerant yeast strain (Saccharomyces cerevisiae NRRL Y-50049) and its non-tolerant parental strain (Y-12632) under synergistic furfural and HMF stress.
• Compared gene expression patterns, focusing on pathways related to glucose metabolism, cofactor regeneration, and aldehyde reduction.

Main Results:

• The tolerant strain Y-50049 demonstrated significant tolerance, in situ detoxification of furfural and HMF, and sustained ethanol production, unlike the parental strain.
• Y-50049 exhibited an enriched genetic background with significantly higher transcript abundance for at least 16 genes compared to Y-12632.
• Enhanced expression of ZWF1 favored the pentose phosphate pathway over glycolysis, accelerating NAD(P)H generation, which supported aldehyde reduction and cofactor regeneration.

Conclusions:

• The acquired tolerance and detoxification capabilities of Y-50049 are attributed to its enriched genetic background and a well-maintained redox balance.
• Reprogrammed gene expression, particularly involving ZWF1, GND1, GND2, TDH1, and ALD4, is critical for NAD(P)H regeneration and functional aldehyde reduction under inhibitor stress.
• This study reveals significant gene interactions and regulatory networks essential for yeast resilience and detoxification in lignocellulosic ethanol production.