After pitched into chilled and aerated wort, brewing yeast will initiate assimilating
fermentable sugars, amino acids, minerals, and other nutrients. From this time
forth, the yeast starts excreting a wide range of compounds such as ethanol, CO2,
higher alcohols, and esters, as a result of cellular metabolism. Whereas the large
cut of these metabolic by-products are toxic for the yeast cells at higher concentrations,
they are the wanted products of beer fermentation at reasonable amounts.
These closed fermenters not only offer
larger productivity and good hygienic standards, but also provide operating advantages
through temperature and pressure control (Landaud et al. 2001).