Simultaneous Saccharification and Fermentation of Hydrothermal Pretreated Lignocellulosic Biomass: Evaluation of Process Performance Under Multiple Stress Conditions Maikon Kelbert 1 & Aloia Romaní 2 & Eduardo Coelho 2 & Francisco B. Pereira 2 & José A. Teixeira 2 & Lucília Domingues 2 Published online: 14 March 2016 # Springer Science+Business Media New York 2016 Abstract Industrial lignocellulosic bioethanol processes are exposed to different environmental stresses (such as inhibitor compounds, high temperature, and high solid loadings). In this study, a systematic approach was followed where the liq- uid and solid fractions were mixed to evaluate the influence of varied solid loadings, and different percentages of liquor were used as liquid fraction to determine inhibitor effect. Ethanol production by simultaneous saccharification and fermentation (SSF) of hydrothermally pretreated Eucalyptus globulus wood (EGW) was studied under combined diverse stress operating conditions (30–38 °C, 60–80 g of liquor from hydrothermal treatment or autohydrolysis (containing inhibitor com- pounds)/100 g of liquid and liquid to solid ratio between 4 and 6.4 g liquid in SSF/g unwashed pretreated EGW) using an industrial Saccharomyces cerevisiae strain supplemented with low-cost byproducts derived from agro-food industry. Evaluation of these variables revealed that the combination of temperature and higher solid loadings was the most signif- icant variable affecting final ethanol concentration and cellu- lose to ethanol conversion, whereas solid and autohydrolysis liquor loadings had the most significant impact on ethanol productivity. After optimization, an ethanol concentration of 54 g/L (corresponding to 85 % of conversion and 0.51 g/Lh of productivity at 96 h) was obtained at 37 °C using 60 % of autohydrolysis liquor and 16 % solid loading (liquid to solid ratio of 6.4 g/g). The selection of a suitable strain along with nutritional supplementation enabled to produce noticeable ethanol titers in quite restrictive SSF operating conditions, which can reduce operating cost and boost the economic fea- sibility of lignocellulose-to-ethanol processes. Keywords Inhibitor compounds . High temperature . High solid loading . Fermentation lignocellulosic biomass . Industrial strain . Hydrothermal treatment Introduction Nowadays, the use of renewable biomass to supply the in- creasing energetic needs and to partially replace fossil fuels is recognized as a suitable alternative to attain a sustainable growth based on a bioeconomy. Liquid fuel (as bioethanol) from lignocellulosic biomass is a promising solution since this raw material is renewable, widespread, and with a huge po- tential for the manufacture of products, without competing with food crops [1]. In order to achieve a cost-effective ligno- cellulosic bioethanol production process, industrial lignocel- lulosic fermentations depend on overcoming specific chal- lenges that differ from conventional food fermentations [2]. These limiting conditions are related with the stages involved in the lignocellulosic process to produce ethanol. Firstly, a pretreatment is necessary to break down the re- calcitrant structure of lignocellulosic feedstock. Hydrothermal treatment, as autohydrolysis or liquid hot water, uses water as the only reaction medium and is considered an environmen- tally friendly pretreatment that improves enzymatic sacchari- fication of lignocellulosic biomass and solubilizes the Maikon Kelbert and Aloia Romaní contributed equally to this work. Electronic supplementary material The online version of this article (doi:10.1007/s12155-016-9722-6) contains supplementary material, which is available to authorized users. * Lucília Domingues luciliad@deb.uminho.pt 1 Chemical Engineering Department, Federal University of Santa Catarina, Florianopolis, SC, Brazil 2 CEB—Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal Bioenerg. Res. (2016) 9:750–762 DOI 10.1007/s12155-016-9722-6