Wow! Assuming that this is not a "troll thread" - and four posts total by a "new" poster all in one thread within a couple of hours certainly smacks of TROLL - the amount of misinformation in this series is staggering.
I thin what the OP is asking about is getting the alcohol level up to a point where competition for the ferment able sugars is removed so that only the yeast is left to continue the fermentation. The "competitors" are cited as being bacteria and enzymes.
First, the bacteria will continue to digest sugars right along side the yeast. Out goal is to provide optimum conditions for growth of the yeast population so that their effects far outweigh the effects of the bacteria. As an analogy, my Dad used to say that a health lawn is the best way to keep weeds down. The idea was that the healthy grass would outcompete the weed for soil, water, nutrients and sunlight, effectively starving the weeds out. That's what we want to do with the yeast, as well.
To do this, we set the fermentation temperature to optimal for the yeast, not higher temperatures the bacteria favor. We oxygenate the wort at the beginning to provide the raw materials for optimal yeast reproduction and population growth. We pitch health doses of clean, pure strain yeast pitches that are properly sized for the volume and specific gravity of the wort.
Once the mash is complete and the wort is on the boil, everything we use that touches the wort is cleaned and sanitized to prevent introduction of unwanted bacteria. We ferment in clean, sanitized vessels to reduce contamination.
In short, we do everything possible to skew the fermentation environment to one most favorable to the yeast.
That is how we affect the competition.
As far as comments about the enzymes, this is an example of a very little learning being dangerous. The mechanisms that control the yeast's metabolism are controlled by enzymes. Enzymes are not some weird pseudo creature crawling around looking for opportunities to create mayhem. They are proteins synthesized by living creatures as part of the creatures way of conducting life. Enzymes moderate and facilitate chemical reactions that are necessary for the production of energy, synthesis of building materials for organism growth, degradation of waste products and all living processes.
In fact, without enzymes at work within the yeast, there would be no alcohol or CO2 in our beer!
I assume that the OP is probably thinking of the enzymes that degrade the long chain carbohydrates into ferment able sugars. If this is the case, the boil has long since destroyed any trace of the amylases. Enzymes, being proteins, are very susceptible to temperatures. The basic structure of the enzymes is broken down above certain temperatures that are specific to each enzyme.
So, if the OP really isn't a troll trying to kick over a hornet's nest, do yourself a favor and get a few simple books on brewing and do some reading. All of this information is available and easily had.
Now...I need to bottle my Rye Porter to free up fermentation chamber space to brew my standard Porter later today.
Carry on, and RDWHAHB!!!
Ian
