Industrial robust yeast isolates with great potential for fermentation of lignocellulosic biomass

The search of robust microorganisms is essential to design sustainable processes of second generation bioethanol. Yeast strains isolated from industrial environments are generally recognised to present an increased stress tolerance but no specific information is available on their tolerance towards inhibitors that come from the pretreatment of lignocellulosic materials. In this work, a strategy for the selection of different yeasts using hydrothermal hydrolysate from Eucalyptus globulus wood, containing different concentrations of inhibitors, was developed. Ten Saccharomyces cerevisiae and four Kluyveromyces marxianus strains isolated from industrial environments and four laboratory background strains were evaluated. Interestingly, a correlation between final ethanol titer and percentage of furfural detoxification was observed. The results presented here highlight industrial distillery environments as a remarkable source of efficient yeast strains for lignocellulosic fermentation processes. Selected strains were able to resourcefully degrade furfural and HMF inhibitors, producing 0.8 g ethanol/Lh corresponding to 94% of the theoretical yield.The authors thank Rosane Schwan (Federal University of Lavras, Brazil) for kindly providing the yeast strains (isolated from Brazilian ''cachaca'' and ''bio-ethanol'' fermentations) and Juan Carlos Parajo and Gil Garrote (University of Vigo, Spain) for assistance in the pre-treatment of lignocellulose biomass. Research described in this article was financially supported by FEDER funds of EU and ''Fundacao para a Ciencia e a Tecnologia'' (FCT), Portugal: Contract PTDC/BIO/66151/2006, Strategic Project PEst-OE/EQB/LA0023/2013, Project ''BioInd - Biotechnology and Bioengineering for improved Industrial and Agro-Food processes, REF. NORTE-07-0124FEDER-000028'' Co-funded by the Programa Operacional Regional do Norte (ON.2 - O Novo Norte), QREN, FEDER and the PhD grant to FP and Pos-Doc grant to AR