Heterothallic S. eubayanus Yeast for High-Frequency Hybridization
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Solution Overview
Problem
Current methods for generating hybrid yeast strains, particularly for lager beer production, face challenges such as limited genotypic and phenotypic diversity, low sporulation capabilities, and low hybridization frequencies, which hinder the introduction of new traits and desired phenotypes in Saccharomyces pastorianus strains.
Innovation Solution
A method involving heterothallic S. eubayanus yeast cells with a mutation in the HO endonuclease gene, allowing efficient mating with other Saccharomyces genus yeast strains, thereby increasing hybridization frequency and enabling the introduction and maintenance of further mutations in a clonal manner.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If standard hybrid generation methods are used, then hybrid yeast strains can be generated, but the hybridization frequency is low (1.5 to 3.6% for mass mating)
Solution Approach 1:
The invention changes the genetic parameter of the S. eubayanus yeast by introducing a mutation in the HO endonuclease gene. This parameter change prevents mating type switching, creating a heterothallic strain that can be efficiently propagated in a clonal manner while maintaining high hybridization frequency when mated with Saccharomyces strains.
Solution Approach 2:
The invention performs preliminary genetic modification of the S. eubayanus strain before hybridization. By pre-establishing the heterothallic characteristic through HO endonuclease mutation, the yeast is prepared in advance to enable efficient clonal propagation and high-frequency hybridization without requiring labor-intensive micromanipulation during the actual mating process.
2Productivity
If genetic modification techniques are used to improve hybridization frequency, then hybridization efficiency increases, but GMO legislation issues and customer acceptance problems arise
Solution Approach 1:
The invention converts a potential harm (low natural hybridization frequency) into a benefit by utilizing a naturally occurring genetic characteristic (HO endonuclease mutation) that prevents mating type switching. This approach achieves high hybridization efficiency while avoiding the creation of transgenic organisms, thereby complying with GMO legislation and maintaining customer acceptance.
3Productivity
If mass mating technique is used, then hybrid appearance chance increases, but genotype and phenotype uncertainty increases and desired traits may be lost
Solution Approach 1:
The invention segments the hybridization process into two distinct stages: first, efficient clonal propagation of the heterothallic S. eubayanus strain to maintain genetic stability and desired traits; second, controlled hybridization with Saccharomyces strains to introduce new variation. This segmentation allows both high efficiency and precise genotype control.
Solution Approach 2:
The heterothallic S. eubayanus strain acts as an intermediary that bridges clonal propagation and hybridization. Its inability to switch mating type ensures genetic stability during propagation, while its compatibility with Saccharomyces strains enables controlled hybridization, thereby maintaining both efficiency and genotype precision.
Data Source
Figure 1A~1B
Figure 2
Figure 3~4
AI summary
The present disclosure relates to a method of generating novel hybrid yeast strains. In particular, it relates to the mating of a S. eubayanus yeast cell with a spore of another yeast strain from the genus Saccharomyces. The disclosure also relates to a S. eubayanus yeast cell comprising a mutant HO endonuclease, and a hybrid yeast strain, where one of the parental strains is said S. eubayanus yeast. The disclosure also relates to a method of producing a beverage using the hybrid yeast strain of the invention.