If any of these are answerable, please let me/us know.

-Bob Devine

1) What is the current status of brewing with immobilized yeast? I've read papers over the past decade on this topic that showed some promise. Will this ever make it into actual use (wasn't there a German brewery that tried it? Granted, this is unlikely to affect us homebrewers directly but it could have a secondary affect if all the majors move to that style of brewing.

RESPONSES:

Clayton: The commercial application of immobilized yeast technology has arrived in the wine industry. Lallemand Inc. has been marketing encapsulated yeast for the past three years. It is a more expensive approach but in certain applications it is worth the added cost:

1.Certain styles of wine require residual sugars of 3 - 5%. It is very difficult and expensive to stop an actively fermenting yeast at an exact residual sugar level. Encapsulated yeast in a bag can easily be removed and the fermentation stops at the desired sugar level.

2. Certain strains of yeast can selectively remove malic acid from the grape fermentation while the main sugar fermentation takes place or has finished. When the desired amount of malate has been consumed, the bag of encapsulated yeast can be removed.

3. Certain genus of yeast that are normally considered spoilage yeast, when used under very controlled conditions, such as bags of encapsulated yeast, can impart the desired level esters, then be removed without contaminating the fermentation and perhaps contaminating the entire winery.

4. Certain powerful yeast can be encapsulated and added to a stuck fermentation to complete the fermentation to dryness.

I imagine that the use of immobilized yeast in the brewing industry will start in speciality beers, where special strains of yeast can be added then withdrawn when desired.

Tobias: There are a couple of groups working on it but as far as I know there are no commercial applications yet. One problem they have is that the beer taste does not meet the requirements although the fermentation itself works reasonably well. I personally don't believe that this will be used by commercial breweries in the next couple of years... but who knows.

2) Genetic engineering has been in the news. Recently, a very simple virus was constructed. Grand claims of moving on to other artificial organisms have been proposed. Are there any groups contemplating building a better yeast?

RESPONSES:

Clayton: Genetically Modified Organisms (GMO) offer great potential. However, GMO is not looked on favorably in the food industry. Lallemand receives many request for letters of assurance that none of our organisms are GMO and that none of products used to produce our products are GMO.

Tobias: Again there are a couple of groups working on genetically modified yeast for different applications including brewing (e.g. faster diacetyl reduction). But I don't know of any brewery using GMO yeast since you have to label it and customers are not open in general to this concept.

3) Why do brewing yeasts die? Is it from lack of nutrients? Damaged cells, maybe from oxidation effects? Telomere limit? Or is there a sinister "lemming" conspiracy here? ;-)

RESPONSES:

Clayton: There are numerous causes but primarily it is due to Stress and old age. Prolong periods in the stationary phase eventually causes a metabolic imbalance resulting in death. Not enough oxygen during the growth phase resulting in a leathery cell wall as the alcohol builds up

preventing the transport systems from bringing in nutrients (sugar) and expelling the alcohol. The build up of alcohol inside the cell becomes stressful and toxic. Lack of certain minerals and vitamins can result in death. Low alcohol beers at 3-5% are much less stressful that high

alcohol beers at 9 -10%. 20% alcohol beer is very stressful. Up to 80% of the yeast die immediately due to the high osmotic pressure. Repeated and poor control of the acid wash stresses the yeast and can cause some of the cells to die. Buds and young daughter cells seem to be more susceptible to mishandling of acid washes. Yeast can multiply about 20 times before the bud scars on the surface of the cell become so great that there is no more room for another bud. This cell will soon die. Most stresses are accentuated as the temperature rises, during fermentation and storage.

Tobias: Yeast is like any other living organism... it ages and eventually dies. Any stress will shorten the lifespan. This can be oxidative stress but also nutrient deficiency, thermo stress, osmotic pressure, alcohol....

4) Are the number of yeast strains increasing or decreasing? Have brewers winnowed down the number of active strains? Or are new and beneficial mutations still being developed?

RESPONSES:

Clayton: I will let Tobias speak for the brewing industry since he was at one time in charge of a yeast collection for a brewing school. I will comment on the wine industry. 20 years ago we marketed three strains of wine yeast taken from a university culture collection. Today we have over 500 strains in our culture collection and market over 100 strains, all isolated from active fermentations at premium wineries through out the world. A few were isolated from the soil of premium vineyards. Each strain has a particular characteristic that is desirable for a certain style of wine.

The opportunity to obtain new strains of wine yeast is much greater that beer yeast because of the natural micro flora of grape juice verses beer wort. Beer wort is sterile, so there is very little chance in isolating a new strain from an actively fermenting beer wort. It is possible to isolate a new strain that has adapted or mutated. Grapes harvested from an open vineyard are loaded with micro organisms from the soil, wind, insects, hands, equipment, crushers, etc. There is no pasteurization stage. The acid pH, osmotic pressure and alcohol eliminates all but a select few yeast and bacteria which end up doing the fermentation. Every vineyard, every winery, every grape varietals, every fermenter, every season offers the potential of us isolating a new and exciting strain.

Nature has thousands of strains that have never been touched. We are beginning to isolate beer strains in wineries (Italy)that produce very good wine. The goal of using commercially produced naturally isolated strains of wine yeast is to overwhelm the indigenous micro flora in each fermenter with a specific strain of yeast.

There are numerous strains of our wine yeast that produce excellent beer and I believe offer the brewing industry a new source of yeast for brewing. There is a mind set by many brewers that wine yeast will make the beer taste like wine. That mind set will be a stumbling block to finding new strains of yeast for beer production.

Tobias: In theory the number of strains should still increase through natural mutation. But breweries are selecting the yeast to fit their production and desired flavor so I would say the number of strains actually used in larger breweries is declining.