New & Noteworthy
October 16, 2012
Small time craft brewers are always looking for ways to push the envelope of beer taste. They are trying to find variations in beer’s fundamental ingredients — hops, barley, and yeast — that will make their beer distinctive. Of these three, the most important is probably yeast (of course, we’re biased here at SGD!).
Something like 40-70% of beer taste comes from the yeast used to make it alcoholic. This is why brewers search high and low for new strains of yeast that will give their beer that special something which will make it stand out. They have looked on Delaware peaches, ancient twigs trapped in amber, Egyptian date palms, and in lots and lots of other places.
But brewers don’t always have to go far away because sometimes the best yeast is right under their noses. Literally.
A brewery in Oregon found the yeast they were looking for in one of their master brewers’ beards. They are now using this yeast to brew a new beer! This seems uniquely revolting but the beer supposedly is quite tasty. Perhaps if they don’t advertise the source of their yeast, this beer could become popular.
They aren’t sure where the yeast in his beard came from, but they think it may have come from some dessert he ate in the last 25 years or so (he hasn’t shaved his beard since 1978). What would be fun is if his beard wasn’t just an incubator, but a breeding ground for new yeast. Maybe yeast from a dessert from 1982 hooked up with a beer yeast blown into his beard while he was working at the brewery. The end result is a new improved hybrid yeast!
Of course we won’t have any real idea about this yeast until we get some sequence data from it. And all kidding aside, the more yeast that are found that are good for making beer, the better the chances that scientists can home in on what attributes make them beer worthy. So this beard borne yeast may help many beers in the years to come despite its troubling beginning.
Perhaps brewers also need to start searching through more beards to look for likely beer yeast candidates. Beard microbiome project anyone?
June 16, 2012
Biofuels hold the promise to significantly slow down global warming. But this will only be the case if they come from something besides corn.
We don’t want them to come from the parts of other plants we eat, either. Shunting food towards fuel will only jack up food prices and put the lives of the poorest at risk. Policy makers should not have to decide between feeding the poor and running their cars.
No, to make biofuels worth our time, we need to be able to turn agricultural waste, grass, saplings, etc. into ethanol. Unfortunately this stuff is mostly cellulose and lignin and we don’t have anything that can efficiently ferment this “lignocellulosic biomass.”
Many groups are working towards creating strains of Saccharomyces yeast, the predominant fungal organism used for large-scale industrial processes, to do this job. None have yet been created that can do the job well enough to be industrially viable. They are either poor fermentors or are genetically modified so that they include non-yeast genes. Ideally any strain would include only Saccharomyces genes, to avoid the public’s fear and loathing of genetically modified organisms.
This is where a new study in GENETICS by Schwartz and coworkers comes in. This group is working towards engineering a yeast that can ferment the pentoses like xylose that make up a good chunk of this otherwise inedible biomass, using genes that are naturally occurring in Saccharomyces. They haven’t yet created such a yeast, but they have at least identified a couple of key genes involved in utilizing xylose.
The researchers took what seemed to be a straightforward approach. Collect and screen various yeast strains for their ability to grow on xylose and isolate the relevant gene(s) from the best of them. Sounds easy enough except that most of the strains they’ve found are terrible sporulators. This means that they couldn’t use conventional methods to isolate the genes they were interested in and so had to come up with new methods.
First they needed to find some way to get the strain to sporulate. They were able to force sporulation by creating a tetraploid intermediate between the xylose fermenting strain, CBS1502, and the reference strain, CBS7001, by adding an inducible HO gene. During this process, they noticed that the ability to utilize xylose segregated in a 3:1 pattern. This usually means that two genes are involved.
They next needed a way to identify these two genes. What they did was to pool 21 spores that could ferment xylose and 21 that could not. They then purified the DNA from each pool and compared them using high throughput sequencing. They eventually found two genes that were key to getting this yeast to use xylose as its carbon source. (They also found at least two other “bonus” genes that seemed to boost its ability to use xylose).
One of the genes, GRE3, was a known member of a xylose utilization pathway. But the other gene, the molecular chaperone APJ1, was not known to be involved in metabolizing xylose. The authors hypothesize that APJ1 might stabilize the GRE3 mRNA.
These two genes may not be enough to create an industrially viable, xylose fermenting Saccharomyces just yet. But the novel methods of gene isolation presented in this study may allow researchers to find additional genes that might one day get them there. Then we will have a way to get ethanol without the large carbon footprint and without the human cost.
A genetic engineering approach to getting yeast to ferment agricultural waste
February 17, 2012
Let’s face it: low alcohol beer just doesn’t taste that great. This is because the alcohol is either diluted or removed chemically after fermentation. Both methods wreak havoc with a beer’s flavor.
Dr. John Morrissey of University College Cork is trying to change this. His lab is working to generate a strain of yeast that turns some but not all of its sugar into alcohol. That way the beer process is the same, just with less alcohol at the end.
This is different from stopping fermentation early. In that case there are still sugars in the final product which ruin a beer’s taste even more than removing the alcohol! Here the same amount of sugars are used up, it is just that only part of that energy has gone into making the alcohol. Same sugar content, less alcohol.
Although we don’t have all the details because of intellectual property issues, what we do know is that he compared the genomes of yeast species that make a lot of alcohol and those that don’t. In an email he stated that he focused on genes that would affect carbon metabolism without perturbing redox balance in a significant way. Presumably he then swapped the appropriate genes between strains and created his low alcohol strain.
This is not only a godsend for low alcohol beer, but it may be useful for other fermentation processes as well. For example, maybe something similar can be done for low or no alcohol wines which, apparently, are even less tasty than low alcohol beer. Designated drivers everywhere will be thanking Dr. Morrissey profusely if he can make decent tasting, low alcohol drinks a reality.
And apparently it isn’t just designated drivers that want this stuff. Judging by recent upticks in sales of the relatively low quality low alcohol beers currently on the market, there is definitely a market out there for such beverages. A cool science project, decent low alcohol beer and nice profits to boot! Who could ask for more?
How beer is made, from Modern Marvels, www.history.com