Development of second generation ethanol process based on xylose
consumption using non-conventional and recombinant yeasts
Abstract
Fermentation of the pentose fraction from hemicellulosic hydrolysate is
an important challenge to be studied in second generation ethanol (E2G)
production. In this sense, we have tested non-conventional
(Scheffersomyces stipitis and Spathaspora passalidarum)
and recombinant yeast strains (Saccharomyces cerevisiae
recombinant MP-C5 and MP-C5H1) capable to uptake xylose with the aim to
design a strategy for E2G production. Growth tests in different
carbohydrates (glucose, xylose, glucose + xylose and sucrose + xylose)
have shown that the integration of xylose and sucrose presented better
results for all yeast tested, and the co-fermentation of these sugars
provided faster xylose consumption by S. cerevisiae recombinant.
One the other hand, Sp. passalidarum do not present high
performance of sucrose consumption in microanaerobic fermentation
conditions and an intracellular invertase high activity was observed by
this yeast. S. cerevisiae MP-C5H1 presented best performance for
fermentation tests and a batch strategy with high cell density was
designed. By this strategy was possible to achieve high ethanol yield
(0.48 g g-1), titer (53.7 g L-1) and
global ethanol productivity (2.24 g L-1
h-1).