A Growth-Coupled Evolutionary Strategy Enhances Heme Biosynthesis in Saccharomyces cerevisiae

Area of Science:

• Biotechnology
• Microbiology
• Food Science

Background:

• Microbial single-cell proteins (SCPs) require enhanced nutritional and sensory qualities for broader food applications.
• Increasing intracellular heme content in edible microorganisms is a key strategy for improving SCPs.
• Current methods for enhancing heme in SCPs are limited.

Purpose of the Study:

• To adapt the Growth-Acceleration Targeting Evolution (GATE) platform for Saccharomyces cerevisiae to increase heme production.
• To develop a non-genetically modified organism (non-GMO) yeast strain with significantly higher heme content.
• To assess the feasibility of using evolved yeast strains for next-generation meat analogues.

Main Methods:

• Engineered a plasmid in Saccharomyces cerevisiae linking the heme-responsive CYC1 promoter to the growth-promoting PTH1 gene, creating a heme-feedback loop.
• Utilized continuous culture for 100 hours under selective pressure, followed by plasmid curing to isolate the Evol-GATE strain.
• Performed transcriptome analysis and whole-genome sequencing to characterize the evolved strain and confirm its non-GMO status.

Main Results:

• The Evol-GATE strain exhibited a five-fold increase in intracellular heme compared to the parental strain.
• A coordinated upregulation of the heme biosynthetic pathway and associated respiratory genes was observed.
• Whole-genome sequencing revealed minimal genetic alterations, confirming the strain's non-GMO classification.

Conclusions:

• The GATE platform effectively selects for yeast mutants with enhanced heme productivity.
• This approach offers a promising strategy for developing non-GMO SCPs enriched in heme.
• The developed yeast strains hold potential for improving the nutritional and sensory profiles of meat alternatives.