By editing the genomes of yeast, we can make bread with a stronger rise, potato chips that contain fewer potential carcinogens and rice wine that tastes like bananas.
Yeasts have been used in food production for millennia. The microorganisms direct the fermentation process that is important for winemaking, baking and brewing. Food scientists have isolated strains of yeast that work particularly well for specific applications, but at the University of Illinois Urbana-Champaign and his colleagues wanted to use CRISPR gene editing to improve them further.
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They made several gene-edited strains of Saccharomyces cerevisiae, a yeast that is commonly used in the food industry. One strain was designed to make bread rise more than usual. Yeast makes bread puff up and rise because it consumes sugars present in the dough and produces carbon dioxide gas, filling the dough with bubbles. But yeast also converts some of the sugar into ethanol, which doesn鈥檛 contribute to the rise.
In a presentation this week at the in San Francisco, California, Jin said that his team edited the yeast鈥檚 genome so that the process by which it 鈥渟mells鈥� sugar and converts it to ethanol was disrupted. This encouraged the yeast to convert more sugar into carbon dioxide, which involves a different process that was not altered. After rising, bread made with this gene-edited yeast had an 18 per cent larger volume than bread made with conventional yeast.
In another yeast strain, Jin and his colleagues altered a different gene to produce potato chips that contained less of a chemical called acrylamide. Acrylamide forms as some starchy foods are fried and studies in rodents have found that it causes cancer. Although , food companies add steps to their production process to keep levels low.
Some potato chips are made by frying slices of a fermented potato dough. The researchers edited the genome of yeast that is used in that fermentation. They enhanced its natural ability to destroy the compounds in the dough that become acrylamide during frying. Acrylamide levels in the chips made with the modified yeast were up to 78 times lower than those of chips produced using standard yeast strains.
The researchers also found that they could manipulate the flavour of a Korean rice wine called makgeolli by altering the genome of yeasts used in its fermentation. Engineering the yeast to produce more amino acids than normal during fermentation led to makgeolli with a stronger savoury, umami flavour. The researchers confirmed this change by measuring a sevenfold increase in chemicals responsible for this flavour.
Another yeast engineered to produce more molecules called esters produced a wine that a panel of human tasters reported had a more fruity flavour, similar to bananas.
Jin said that the way he and his colleagues genetically edited the yeasts didn鈥檛 require using any DNA that was foreign to the yeasts so the foods made with them may raise fewer health and safety concerns. This could mean that their yeasts will require less stringent regulation than some genetically modified foods.
鈥淚 would argue that these modified yeast strains are equivalent to natural mutants,鈥� he said at the conference.
