Persistent Recombinant Yeast for Contamination-Resistant Ethanol Fermentation
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Solution Overview
Problem
Continuous fermentation processes in the Brazilian fuel ethanol industry face challenges with wild yeast contamination, leading to decreased ethanol yields and productivity losses due to the heterozygous nature of Saccharomyces cerevisiae strains and genomic rearrangements, which complicate molecular identification and allow other Saccharomyces strains and non-Saccharomyces yeasts like Dekkera bruxellensis, Candida krusei, and Schizosaccharomyces pombe to proliferate.
Innovation Solution
Development of recombinant yeast host cells with phenotypic traits such as fast settling, rugose phenotype, improved invertase activity, triploidy, and increased signaling in the RAS/cAMP/PKA pathway, enhancing persistence and reducing contamination through genetic modifications that modulate polypeptide activity and expression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If recycled biomass is used for continuous fermentation cycles, then productivity is improved, but wild yeast contamination increases
Solution Approach 1:
The patent applies parameter changes by modifying yeast strain characteristics through genetic engineering and selection for specific phenotypic traits (fast settling, rugose phenotype, improved invertase activity, triploidy, increased RAS/cAMP/PKA signaling). These parameter changes enable the yeast to outcompete wild yeasts in continuous fermentation cycles, maintaining high productivity while reducing contamination.
Solution Approach 2:
The patent employs a disposable approach by using single-use sterile filters and consumable materials in the fermentation process. This prevents contamination from persisting across cycles, allowing the recycled biomass to maintain high productivity without carrying over harmful contaminants.
2Productivity
If Saccharomyces cerevisiae strains are used for fermentation, then ethanol production is efficient, but genomic rearrangements complicate molecular identification
Solution Approach 1:
The patent utilizes phenotypic changes including rugose colony morphology and color variations in yeast colonies as visual markers for identification. This allows researchers to distinguish engineered strains from wild yeasts and monitor population dynamics without relying on complex molecular methods, simplifying detection while maintaining production efficiency.
Solution Approach 2:
The patent replaces complex molecular identification systems (microsatellite analysis, RAPD, PFGE) with simpler phenotypic observation methods. By substituting mechanical/molecular analysis with visual and physiological characteristics, the system maintains efficient ethanol production while dramatically reducing identification complexity.
3Duration of action of moving object
If fermentation cycles are extended for biomass recycling, then productivity increases, but contamination by non-Saccharomyces yeasts increases
Solution Approach 1:
The patent applies preliminary action by pre-selecting and pre-engineering yeast strains with desirable phenotypic traits before they enter continuous fermentation. These pre-modified strains are more resistant to contamination and can maintain population stability over extended cycles, preventing non-Saccharomyces yeasts from establishing themselves.
Solution Approach 2:
The patent converts the potential harm of extended fermentation (contamination risk) into a benefit by using the prolonged exposure to selective pressures to enrich for strains with superior persistence and contamination resistance. The extended cycles become a selection mechanism that favors engineered strains over contaminants.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The recombinant yeast cells maintain a high persistence of at least 99% in fermenting populations after 40 cycles, improving ethanol yield and reducing glycerol production, while minimizing contamination and maintaining fermentation efficiency.
Implementation Method 1
The present disclosure concerns yeast host strains exhibiting prolonged persistence during a plurality of fermentation cycles
Implementation Method 2
The yeasts are recycled using continuous centrifugation and acid washing to improve productivity
Implementation Method 3
an improved invertase activity
Data Source
AI summary
The present disclosure provides yeasts, which can be recombinant yeast host cells, exhibiting prolonged persistence when submitted to a plurality of fermentation cycles. The yeasts exhibit at least one of the following phenotypic trait: a fast settling phenotype, a rugose phenotype, an improved invertase activity, triploidy, increased signaling in a RAS/cAMP/PKA pathway or combinations thereof.