Programs for isolation and selection of yeast strains have had
positive results, due to higher yields of fermentation. The decrease
in glycerol production and foaming resulted in higher levels of
ethanol production and the consequent reduction in production
costs. The rich biodiversity of yeasts found in environments of
ethanol plants production could be an important source of new
strains. This is due to, among other factors, the selective pressure on
the cells which occurs during the recycling of yeast cells generates
strains with increased tolerance to stress conditions in industrial
fermentation: high concentrations of ethanol, sugar and CO2
pressure and low O2pressure and low pH[10]