Description
Background: The optimization of industrial bioethanol production will depend on the rational design and
manipulation of industrial strains to improve their robustness against the many stress factors affecting their
performance during very high gravity (VHG) or lignocellulosic fermentations. In this study, a set of Saccharomyces
cerevisiae genes found, through genome-wide screenings, to confer resistance to the simultaneous presence of
different relevant stresses were identified as required for maximal fermentation performance under industrial
conditions.
Results: Chemogenomics data were used to identify eight genes whose expression confers simultaneous
resistance to high concentrations of glucose, acetic acid and ethanol, chemical stresses relevant for VHG
fermentations; and eleven genes conferring simultaneous resistance to stresses relevant during lignocellulosic
fermentations. These eleven genes were identified based on two different sets: one with five genes granting
simultaneous resistance to ethanol, acetic acid and furfural, and the other with six genes providing simultaneous
resistance to ethanol, acetic acid and vanillin. The expression of Bud31 and Hpr1 was found to lead to the increase
of both ethanol yield and fermentation rate, while Pho85, Vrp1 and Ygl024w expression is required for maximal
ethanol production in VHG fermentations. Five genes, Erg2, Prs3, Rav1, Rpb4 and Vma8, were found to contribute to
the maintenance of cell viability in wheat straw hydrolysate and/or the maximal fermentation rate of this substrate.
Conclusions: The identified genes stand as preferential targets for genetic engineering manipulation in order to
generate more robust industrial strains, able to cope with the most significant fermentation stresses and, thus, to
increase ethanol production rate and final ethanol titers.
; Guimarães, Pedro M. R. 
