Using a technique that cuts out unwanted copies of a genome to improve the beneficial properties of a compound, researchers working at the University of Illinois College of Agricultural, Consumer, and Environmental Services (ACES) claim to have produced a yeast that could vastly increase the quality of wine while also reducing its hangover-inducing properties.
"Fermented foods – such as beer, wine, and bread – are made with polyploid strains of yeast, which means they contain multiple copies of genes in the genome," said Associate Professor of microbial genomics at the University of Illinois, Yong-Su Jin. "Until now, it’s been very difficult to do genetic engineering in polyploid strains because if you altered a gene in one copy of the genome, an unaltered copy would correct the one that had been changed,"
So the researchers developed what they call a "genome knife," which allowed them to slice across multiple copies of a target gene until all the copies were cut, thereby making it impossible for any remaining genomes to correct any altered ones.
After being completely cut, the enzyme RNA-guided Cas9 nuclease was then employed to carry out precise metabolic engineering on strains of polyploid Saccharomyces cerevisiae, a species of common yeast instrumental in winemaking, bread baking, and beer brewing.
This newly-modified strain, the team believes, is a breakthrough of "staggering" proportions. The applications of this compound possibly range in the thousands, given the ubiquity of the species of yeast and its use in a myriad different industries.
"Wine, for instance, contains the healthful component resveratrol,” said Associate Professor Jin. "With engineered yeast, we could increase the amount of resveratrol in a variety of wine by 10 times or more. But we could also add metabolic pathways to introduce bioactive compounds from other foods, such as ginseng, into the wine yeast. Or we could put resveratrol-producing pathways into yeast strains used for beer, kefir, cheese, kimchee, or pickles – any food that uses yeast fermentation in its production."
But more than this, if winemakers were to clone this new enzyme, then they could use it to improve malolactic fermentation (the conversion of bitter malic acid, naturally present in freshly pressed grapes, into softer-tasting lactic acid) to produce a consistently smoother wine while also removing the toxic byproducts that can cause hangovers.
The scientists see the capability of their genome knife in this situation as an absolute must in engineering the extremely precise engineered mutations required to achieve this improvement in wine fermentation.
"Scientists need to create designed mutations to determine the function of specific genes," said Jin. "Say we have a yeast that produces a wine with great flavor and we want to know why. We delete one gene, then another, until the distinctive flavor is gone, and we know we’ve isolated the gene responsible for that characteristic."
Optimistically, the researchers also believe that their nascent technology could make genetic engineering and genetically modified organisms more palatable to the wider community.
"In the past, scientists have had to use antibiotic markers to indicate the spot of genetic alteration in an organism, and many persons objected to their use in foods because of the danger of developing antibiotic resistance," concluded Jin."With the genome knife, we can cut the genome very precisely and efficiently so we don’t have to use antibiotic markers to confirm a genetic event."
The results of this research was recently published in the journal Applied and Environmental Microbiology.
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