# Breeding of yeast strains with intracellular amino acid accumulation for value-added alcoholic beverages

## TL;DR

Scientists are breeding yeast to produce more amino acids, which can enhance the flavor of alcoholic drinks like sake and beer.

## Contribution

The paper introduces a plasmid-free genome editing system for precise metabolic pathway modification in yeast.

## Key findings

- Mutagenesis of brewing yeast leads to overproduction of branched-chain amino acids and phenylalanine.
- Altered feedback regulation and transcriptional control explain increased amino acid production in mutants.
- A plasmid-free genome editing system allows precise metabolic pathway modifications without foreign DNA.

## Abstract

The yeast Saccharomyces cerevisiae converts amino acids into volatile compounds with fruity and floral aromas during fermentation. These amino acid-derived aroma compounds play a critical role in defining the taste and flavor of alcoholic beverages such as sake, beer, and wine. The productivity of amino acid-derived aroma compounds depends on the intracellular availability of their precursor amino acids. Therefore, breeding yeast strains that accumulate amino acids provides a practical approach to developing alcoholic beverages with more unique and attractive sensory characteristics. In this minireview, we describe the isolation of yeast strains that overproduce branched-chain amino acids and phenylalanine, obtained through conventional mutagenesis of industrial brewing yeasts. We also discuss the mechanisms responsible for the increased production of these amino acids in the mutant strains, including altered feedback regulation and transcriptional control of key enzymes involved in their biosynthesis. In addition, we briefly introduce a plasmid-free genome editing system that enables precise modification of metabolic pathways without the integration of foreign DNA, allowing the construction of strains that are not classified as genetically modified organisms. This method represents a promising tool that allows flexible and fine-tuned engineering of yeast metabolic pathways, including the development of strains with tailored aroma profiles.

This minireview summarizes our recent work on breeding amino acid-overproducing yeast strains by conventional mutagenesis for value-added alcoholic beverage production, along with elucidating the mechanisms responsible for amino acid overproduction in these mutants.