There comes a day in every parent’s life when the towheaded young moppet turns his saucer-sized eyes upwards and asks, “Daddy, where does beer come from?”
If you’re like most of us you’ll punt and say “Milwaukee.” Better-prepared parents explain how a delicate balancing act allows living yeast to metabolize the sugar in barley malt and boiled hops flowers into carbon dioxide and alcohol. The more insatiable moppets will want to know why, exactly, yeast makes alcohol in the first place when it’s much more energetically efficient to metabolize sugar directly to carbon dioxide, and now you’re stuck. Do you admit that parents don’t in fact have the pope’s infallibility and twice his judgment? Make something up on the spot? If you’ve stayed up in bed worrying about that scenario, science has your back.
The journal Nature (subscription wall) recently ran a series on science and alcohol from which I plan to steal shamelessly. Today’s vignette answers in the most ultimate sense where alcohol comes from. Besides Milwaukee, I mean.
Based in UF Gainesville, Steven Benner (homepage) decided to take an evolutionary approach to the question. To wit, when exactly did the party start?
The story begins, of course, with yeast. We all have some version of the gene alcohol dehydrogenase (ADH), which breaks down alcohol and certain acids in the liver. The very low alcohol tolerances of Asians and Native Americans, for example, come from having lower levels of ADH protein. Unlike most of us yeast have two ADH genes – ADH1 runs in reverse, converting sugar into alcohol while ADH2 converts alcohol back into energy. Cool, but what’s the point? It uses up a lot more energy to convert sugar into alcohol and then convert alcohol into energy than it does to convert sugar into energy directly. So something other than energetics had to give yeast the selective push they needed to start making booze.
[Nature 438, 1068-1069 (22 December 2005)]
Benner and his team came across the explanation when hunting for the origins of ADH in yeast. Benner is interested in combining the study of genes and proteins with geology and palaeontology to gain insight into the history of life on Earth and present-day protein function. “Every biomolecule is better understood if we know its history as well as its structure,” he says.
The ADH genes in yeast make an intriguing subject for this approach. When yeast gained its ability to make alcohol, it must have done so as a result of a selection pressure in its environment and, what is more, this would have had a knock-on effect on other creatures. So working out when and how the ADH enzymes came to be could open a small window onto what ecosystems were like back then.
…From a database of the sequences of related ADH genes in various yeasts — combined with additional ADH genes specially sequenced for this study — Benner and his colleagues assembled an evolutionary tree of yeast ADH…The supposed ancestor [ADH gene] turned out to be most similar to modern-day ADH1, the one that helps yeast make alcohol.
The same evolutionary tree helped the team to estimate when the ancestor gave rise to the two present ADH genes. This information offers some insight into what drove the strategy. Was it humans breeding yeasts and selecting them to accumulate alcohol? Or did the event take place long before that?
The group found that duplication of the ancestral gene took place between 80 million and 60 million years ago, which means that humans could not have had anything to do with it. Rather, Benner thinks it was down to flowering plants.
…With their temptingly large amounts of sugar, the fruit called for a clever strategy. “Yeast ‘realized’ there was a lifestyle opportunity, which involved making large amounts of alcohol as a way of defending the resources against competing organisms,” Benner explains. Yeast ‘realized’ there was a lifestyle opportunity, which involved making large amounts of alcohol.
In other words, yeast came up with a way of ‘pickling’ the fruit by producing alcohol, which would have made the fruit toxic to its competitors. This had a knock-on effect on its wider ecosystem: as well as killing off its competitors, yeast had created a niche in fermenting fruit for any organism that could devise a way to cope with the alcohol.
This sort of evolutionary challenge rarely goes unanswered. Fruit-eating insects developed their own ADH gene and, adding insult to injury, use it to convert ethanol into usable metabolic energy (ours doesn’t do that). An interesting side-effect of this ongoing arms race is that the distribution of fruit fly ADH genes can indicate climate change because climate plays a major role in determining which yeast grow on which fruit.
Ergo the answer to where beer comes from, back to its evolutionary origins, is fruit, and a hairbrained plot by yeast to hog it for themselves.
In honor of John’s diet today’s non-beer alternative covers the recent appearance of “low-carb” wines. Carbs in wine generally isn’t a problem, weighing in at 3 or 4 grams per five-ounce glass, but if you’re hardcore about inducing ketosis and possible kidney damage (features, not bugs, of the Atkins lifestyle) this is the way to go.
Jill Jepson of Brown-Forman wines and maker of the now-ubiquitous one.6 Chardonnay and one.9 Merlot, describes how she works her vinicultural magic:
Last summer, Jepson says, Brown-Forman analyzed various lots of grapes from their growers throughout California and chose the ones with the fewest carbs from 2002 merlot juice and 2003 chardonnay fruit.
Then they dry-fermented the wine to remove every bit of residual sugar. (Most wine has just a touch left over.) And they blended it to achieve what Jepson describes as a “really interesting, fruity style.”
One.6 generally ranked second or last among our newsroom tasters. They found “almost no nose,” and “no fruit.” Some said it tasted “bland” and “mild”; a couple found it “sweet” and “more like pop than wine.”
About the Merlot a taster replied: “Kind of stagnant, but I could finish this.” I’m sure they’ll be printing that on their label.
There may be good labels out there by now, or due to the waning of the Atkins trend there may not, but this seems like a misguided approach to dieting. A better idea might be to avoid the boxed stuff because of the generally-higher sugar content, find a nice dry bottle and enjoy it in small enough quantities that you can lie to the dietitian about it later. And it goes without saying that wine will always be a better choice for that sort of thing than beer.