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Improved Sugarcane-Based Fermentation Processes by an Industrial Fuel-Ethanol Yeast Strain
Gabriela Muller1, Victor R de Godoy1, Marcelo G Dário1
1Department of Biochemistry, Federal University of Santa Catarina, Florianópolis, Santa Catarina 88040-900, Brazil.
Journal of Fungi (Basel, Switzerland)
|August 25, 2023
Summary
Researchers investigated industrial yeast strains for fuel ethanol and cachaça production in Brazil. Modifying sucrose metabolism enhanced ethanol yield by 11%, demonstrating a strategy to improve fermentation efficiency.
Area of Science:
- Biotechnology
- Industrial Microbiology
- Yeast Genetics
Background:
- Brazilian fuel ethanol and cachaça production relies heavily on *Saccharomyces cerevisiae* strains fermenting sucrose-rich broths.
- Feedstock sugar prices significantly impact the economics of these bioprocesses.
- Understanding yeast genetic adaptations, particularly for sucrose utilization, is crucial for process optimization.
Purpose of the Study:
- To determine the genetic characteristics of industrial *Saccharomyces cerevisiae* strains used in Brazilian fuel ethanol and cachaça production.
- To investigate the role of invertase gene copy number and activity in sucrose fermentation efficiency.
- To engineer a yeast strain for improved direct sucrose consumption and enhanced ethanol production.
Main Methods:
- Array comparative genomic hybridization (aCGH) was employed to analyze the genomes of eight fuel-ethanol and five cachaça industrial yeast strains.
- Invertase activity assays were performed to correlate enzyme levels with strain genetics.
- Metabolic engineering involved modifying sucrose metabolism by controlling extracellular invertase and enhancing intracellular invertase and sucrose transport via *AGT1*.
Main Results:
- Only two of the analyzed industrial strains exhibited amplification of invertase genes, with high specific activity.
- Most strains possessed a single *SUC2* locus, suggesting invertase activity is not a primary limitation in sucrose fermentation for these yeasts.
- The engineered strain achieved 11% higher ethanol production from sucrose by directly consuming the disaccharide, bypassing extracellular hydrolysis.
Conclusions:
- Invertase gene amplification is not a universal adaptation in Brazilian industrial yeasts for sucrose fermentation.
- Direct cellular consumption of sucrose, facilitated by engineered intracellular invertase and permease activity, offers a viable strategy for increased ethanol yield.
- This metabolic engineering approach presents a promising avenue for optimizing fuel ethanol and cachaça production economics.
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