Adaptive Yeast Strains for Low Ethanol Wine Fermentation
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Solution Overview
Problem
The wine industry faces challenges in reducing ethanol content in wines due to high sugar content in grapes, leading to increased alcohol levels, which affect sensory quality and can result in sluggish fermentations, and existing solutions like genetic engineering are hindered by consumer acceptance of GMOs.
Innovation Solution
A process involving adaptive laboratory evolution using hyperosmotic stress with potassium chloride to redirect carbon flux in yeast strains, resulting in increased glycerol production and decreased ethanol production, without genetic modification, thereby obtaining variant yeast strains that produce more glycerol and less ethanol during fermentation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If genetic engineering is used to redirect carbon flux towards glycerol production, then ethanol production is reduced, but consumer acceptance is poor due to GMO concerns
Solution Approach 1:
The invention changes the parameters of yeast cultivation by exposing yeast to hyperosmotic stress conditions (high salt concentrations) during adaptive evolution, which naturally selects for strains that produce more glycerol and less ethanol without genetic modification. This parameter-based approach achieves the desired metabolic shift through environmental selection rather than genetic engineering.
Solution Approach 2:
The yeast population performs self-selection through adaptive evolution under controlled stress conditions. The hyperosmotic stress environment naturally favors mutants with enhanced glycerol production capacity, allowing the system to self-optimize without external genetic intervention. This eliminates the need for GMO techniques while achieving the same metabolic outcome.
2Quantity of substance
If physical de-alcoholisation techniques like reverse osmosis or distillation are used, then ethanol content is reduced, but organoleptic quality of wine deteriorates and implementation cost increases
Solution Approach 1:
The invention performs preliminary action by modifying the yeast strain's metabolic properties before fermentation occurs. By using adaptive evolution to pre-select yeast strains with reduced ethanol production capacity, the system prevents excessive ethanol accumulation at the source, eliminating the need for post-fermentation de-alcoholisation treatments that compromise wine quality.
Solution Approach 2:
The invention converts the harmful effect of hyperosmotic stress (which normally inhibits yeast growth) into a beneficial selection pressure that favors yeast mutants with improved glycerol production and reduced ethanol output. The stress condition that would normally be detrimental becomes a tool for obtaining desirable low-ethanol yeast strains.
3Quantity of substance
If high sugar content grapes are used to meet consumer demand for rich fruit flavor, then alcohol content increases, but this leads to sluggish fermentations and sensorial quality degradation
Solution Approach 1:
The invention changes the yeast's metabolic parameters through adaptive evolution under hyperosmotic stress, selecting for strains that efficiently produce glycerol as an alternative carbon sink. This parameter modification allows the yeast to handle high sugar loads without producing excessive ethanol, preventing fermentation slowdowns and maintaining reliability even with high-sugar grapes.
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 process effectively reduces ethanol content by 0.40% to 2.00% v/v in wines while maintaining or improving viability and fitness under hyperosmotic stress, without producing undesirable compounds that alter organoleptic properties.
Implementation Method 1
a salt capable of causing an hyperosmotic stress to the ancestral yeast strain
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 2
AI summary
The present disclosure concerns a process for obtaining a variant yeast strain capable of producing less ethanol in an alcoholic fermentation process than its corresponding ancestral strain. The variant yeast strain is obtained by culturing the ancestral strain in the presence of increasing concentrations of a salt capable of causing an hyperosmotic stress to the ancestral yeast strain. The present disclosure also concerns variant yeast strain obtained from this process (for example the variant yeast strain deposited at Institut Pasteur, on January 9, 2014, under accession number CNCM I-4832, the variant yeast strain deposited at Institut Pasteur, on October 18, 2012 under accession number CNCM I-4684, the variant yeast strain deposited at Institut Pasteur, on October 18, 2012 under accession number CNCM I-4685 and/or the variant yeast strain deposited at Institut Pasteur on January 28, 2015 under accession number CNCM I-4952) as well as processes using the variant yeast strain (wine fermentation for example).