Saccharomyces cerevisiae is the main species of yeast employed
for ethanol production at industrial level since this microorganism
is easy to handle, shows no high nutritional needs, can produce
ethanol concentrations above 15% [8], tolerates high concentrations
of sugars, is not expensive, produces low levels of by-products, is
osmotolerant and presents high viability for recycling [9].
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 O2 pressure and low pH [10].
This paper deals with the isolation of yeasts from molasses and
grapes, and further evaluation of bioethanol production in commercial
media. Selected strains were taxonomically characterized
and assayed for optimizing some operational variables and the use
of sugarcane molasses as economic fermentative medium. Finally,
the no flocculent A2 strain was employed to scale up the process