MAT GODDARDThe distinct regional conditions, or terroir, in which grapes are grown are thought to shape a wine’s character. But strict scientific evidence of this phenomenon has been lacking. Now, researchers in Auckland, New Zealand, have confirmed that at least one aspect of terroir—local differences in yeast strains—does indeed alter the outcome of Sauvignon Blanc fermentation. Their findings were published today (September 24) in Scientific Reports. 
 
 “The take-home message of this paper is that different strains of yeast used to ferment grapes impart a specific chemistry to the wine,” said microbiologist Jack Gilbert of the Argonne National Laboratory in Illinois who was not involved in the work. “The wine community understands that yeast play a role [in terroir]—that the yeast on the plant could be giving a particular strain of Merlot grown in two different locations two different flavors,” he added, but there was no formal proof. “This is just a wonderful piece of evidence that shows the types of metabolites those different strains of yeast can actually generate in the ferment.” 
 
 Grape must—the freshly crushed fruit, seeds, skins, and stems of harvested vines—can be turned into wine either by inoculating with a pure yeast culture or by allowing the microbes naturally present on the fruit to carry out spontaneous fermentation. It is well known that these naturally occurring microbes exhibit regional variations, said Matthew Goddard of the University of Auckland and the University of Lincoln in the UK. But it was unclear whether these differences translated to distinct wine flavors and aromas, he said. “This study attacks that question.” 
 
 Goddard’s Auckland-based team first identified and isolated the six major related strains of the yeast Saccharomyces cerevisiae present at each of six New Zealand wine-producing regions. The researchers then inoculated these 36 strains individually into sterilized Sauvignon Blanc grape juice to begin fermentation. “We controlled for absolutely everything else other than these microbes,” he said, “and then we asked: What are the wines that result from those strains?” 
 
 The wines were tested for the presence and quantity of 39 volatile compounds and other standard quality parameters such as ethanol, acidity, and sugar. The researchers found that the chemical signatures of the wines showed a large degree of overlap, but that the profiles of those produced by yeast strains from the same region tended to cluster—indicating the wines did indeed exhibit a regional character. 
 
 The most distinct regional signature, the team discovered, belonged to those wines produced by strains of yeast from Nelson—located at the northern end of New Zealand’s South Island. The wines shared “a collection of compounds that stood out,” said Goddard. “Putting my subjective and less scientific hat on,” he added, “this wouldn’t be a massively unexpected result for tasters [because] wines from Nelson do tend to have a certain something about them. They have a different profile.” 
 
 The lab-generated Nelson wines had particularly high concentrations of compounds that are known to impart apple and sweet fruit sensory effects. However, the wines’ actual tastes were not verified, in part because of health and safety restrictions, explained Goddard. 
 
 The effects of the microbes on the wines’ chemical profiles were statistically significant, “but the size of that effect was still relatively small,” said Goddard. But that would be expected, he said, because presumably the local differences in yeast are just one of numerous factors contributing to a wine’s terroir. 
 
 “This is the first quantitative demonstration of a microbial component of terroir,” said oenologist Vladimir Jiranek of the University of Adelaide, who did not participate in the study. “It starts to explain the basis for that uniqueness [which] is nice to know,” he said, “but of course from a wine research point-of-view, what we want to do is to manipulate that profile of microbes to favor a particular wine-making outcome.” 
 
 For instance, Gilbert suggested, “we could add in yeast . . . of our own particular design to create particular desired organoleptic properties for the wine.” If microbial manipulation were combined with other terroir-contributing factors, he added, “you could theorectically create the ideal year every year.” 
 
 S. Knight et al., “Regional microbial signatures positively correlate with differential wine phenotypes: evidence for a microbial aspect to terroir,” Scientific Reports, 5:14233, doi:10.1038/srep14233, 2015. ||||| Wine (Shuttershock) 
 
 Being a winemaker is a specialised calling, requiring intimate knowledge of soil composition, seasons and weather, chemistry, flavour, even marketing and sales. 
 
 Yet the distinctive bouquet and flavour of a Chablis or chardonnay could not be achieved without the input of a brainless, single-celled organism, said a study Thursday. 
 
 The previously overlooked vintner, a type of yeast called Saccharomyces cerevisiae, makes a “small but significant” contribution to a wine’s flavour and taste, scientists reported in the journal Scientific Reports. 
 
 This makes the fungus a key to that enigmatic wine concept “terroir” — everything from the soil, topography, climate and agricultural processes that go into producing your favourite Bordeaux. 
 
 “I was surprised that we detected any signal at all from these geographically different yeast populations in the aroma profile of the wine — I thought we would not,” co-author Matthew Goddard of the University of Lincoln in England told AFP. 
 
 “The signal is small, but detectable,” he said by email. 
 
 Geographic differences in wines were previously ascribed mainly to plant genetics, local soil and climate, and farming methods. 
 
 – ‘Fruity notes’ are mostly yeast – 
 
 “The idea that microbes might play a role in terroir is new, and we think this is the first time that it has been experimentally shown that this is the case,” said Goddard. 
 
 For the study, the team first showed genetic differences between populations of S. cerevisiae found in sauvignon blanc grapes in six major wine-growing regions of New Zealand. 
 
 Then they tested whether these genetic differences influenced the taste and smell of wine. 
 
 They found that roughly half of the chemical compounds that determine a wine’s unique traits came from yeast during fermentation — “most of the ‘fruity’ notes in wine are in fact derived from yeast not the fruit,” Goddard said. 
 
 The compounds are a by-product of fermentation. 
 
 Some winemakers add yeast to grape juice for fermentation, but many rely on microbes naturally found in the fruit, he added. 
 
 “I note that many (but not all) premium wines are made by spontaneous fermentation, and I think the microbes contribute something to the distinctness (and thus value) of these.” 
 
 Wine is still mainly a product of terroir, said Goddard — “we just have to widen our concept of what is included in terroir to the other living things in the region — like the microbes.” 
 
 Further study is needed to determine whether other fungi and bacteria may also be contributing to regional wine characteristics, the authors said. ||||| URBANA - University of Illinois scientists have engineered a "jailbreaking" yeast that could greatly increase the health benefits of wine while reducing the toxic byproducts that cause your morning-after headache. 
 
 "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. 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," said Yong-Su Jin, a U of I associate professor of microbial genomics and principal investigator in the Energy Biosciences Institute. 
 
 Recently scientists have developed a "genome knife" that cuts across multiple copies of a target gene in the genome very precisely--until all copies are cut. Jin's group has now used this enzyme, RNA-guided Cas9 nuclease, to do precise metabolic engineering of polyploid Saccharomyces cerevisiae strains that have been widely used in the wine, beer, and fermentation industries. 
 
 The possibilities for improved nutritive value in foods are staggering, he said. "Wine, for instance, contains the healthful component resveratrol. 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." 
 
 Another benefit is that winemakers can clone the enzyme to enhance malolactic fermentation, a secondary fermentation process that makes wine smooth. Improper malolactic fermentation generates the toxic byproducts that may cause hangover symptoms, he said. 
 
 Jin stressed the genome knife's importance as a tool that allows genetic engineers to make these extremely precise mutations. 
 
 "Scientists need to create designed mutations to determine the function of specific genes," he explained. "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." 
 
 The new technology also makes genetically modified organisms less objectionable, he said. "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. 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 research was reported in a recent issue of Applied and Environmental Microbiology. 
 
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 Co-authors of "Construction of a Quadruple Auxotrophic Mutant of an Industrial Polyploid Saccharomyces cerevisiae Strain by Using RNA-Guided Cas9 Nuclease" are Guochang Zhang, In Iok Kong, Heejin Kim, Jingjing Liu, and Yong-Su Jin, of the University of Illinois at Urbana-Champaign, and Jamie H.D. Cate of the University of California, Berkeley, and Lawrence Berkeley National Laboratory. The research was funded by the Energy Biosciences Institute.
– Winemakers have long understood that things like the soil in which grapes are grown can affect the flavor of the grapes and, ultimately the wine. Now scientists have proof that a microbial component of "terroir"—wine lingo for the individual regional conditions—has an impact, too. Reporting in the journal Scientific Reports, researchers say they isolated the six major related strains of the yeast Saccharomyces cerevisiae (yeast is a microbe, which the AFP describes as a "brainless, single-celled organism") found at all six of New Zealand's wine-producing regions and inoculated those 36 strains into sterilized Sauvignon Blanc grape juice to begin the process of fermentation. "We controlled for absolutely everything else other than these microbes," one researcher tells The Scientist, "and then we asked: What are the wines that result from those strains?" The intention was to see whether the genetic differences in the strains had an impact on the wine's taste and smell, but instead of using subjective taste testing, the researchers chemically profiled the resulting wines. And while these signatures showed tons of overlap, they also betrayed regional distinctiveness, with the profiles of wines produced by yeast strains from the same region clustering together. It wasn't the result study co-author Matthew Goddard was expecting. "The idea that microbes might play a role in terroir is new," he tells AFP, "and we think this is the first time that it has been experimentally shown that this is the case." The researchers further determined that "most of the 'fruity' notes in wine are in fact derived from yeast not the fruit." (Read about three really detestable wine habits.)