ORIGINAL ARTICLE Bioconversion of soybean and rice hull hydrolysates into ethanol and xylitol by furaldehyde-tolerant strains of Saccharomyces cerevisiae, Wickerhamomyces anomalus, and their cofermentations Nicole Teixeira Sehnem 1 & Lilian Raquel Hickert 1 & Fernanda da Cunha-Pereira 1 & Marcos Antonio de Morais Jr 2,3 & Marco Antônio Záchia Ayub 1 Received: 20 July 2016 /Revised: 20 October 2016 /Accepted: 26 October 2016 /Published online: 8 November 2016 # Springer-Verlag Berlin Heidelberg 2016 Abstract The aims of this work were to evaluate the ability of furaldehyde-tolerant yeast strains Saccharomyces cerevisiae P6H9 and Wickerhamomyces anomalus WA-HF5.5 and their cofermentations and to convert soybean and rice hull hydro- lysates into ethanol and xylitol. In batch shaker cultures, the strains showed the ability to tolerate high osmotic pressure (1918 mOsmkg -1 ), completely depleting furaldehyde in the first 12 h of cultivations, while converting the hydrolysate sugars into ethanol. Highest ethanol yields of 0.37 g g -1 and productivity of 0.31 g L -1 h -1 were obtained in the cofermentation using rice hull hydrolysate as substrate. The concentration of sugars in soybean hull hydrolysate proved to be inadequate as substrate for the cultivation of these strains, showing a low ethanol productivity of 0.08 g L -1 h -1 . Bioreactor cultivations of S. cerevisiae on rice hull hydroly- sate under anaerobiosis showed a relatively high ethanol pro- ductivity of 6.7 g L - 1 h - 1 , whereas the bioreactor cofermentation produced xylitol to yields of 0.86 g g -1 under conditions of oxygen limitation. Keywords Second-generation ethanol . Xylitol . Saccharomyces cerevisiae . Wickerhamomyces anomalus . Lignocellulosic hydrolysates 1 Introduction There is a global effort to increase the production of biofuels, in special ethanol, to reduce the dependence on fossil fuels. First-generation ethanol is mainly produced from food crops such as sugarcane and maize, thus competing for agricultural areas used for food production [1]. In contrast, ethanol derived from lignocellulosic feedstocks (second-generation ethanol) represents a renewable source of energy and offer an environ- mentally important alternative because these materials do not directly compete with food production [2]. Biomass from wood, straws, grasses, and hulls of a variety of vegetables are composed of cellulose, hemicellulose, oils, and lignin and must be treated in order to breakdown their polymeric sugars that make up their complex structure, liberating mono- meric fermentable sugars. Diluted acid hydrolysis is one of the commonest pretreatments used to release sugars and is already in place at pilot scale [3–5]. This pretreatment depolymerises the hemicellulose fraction of biomass at relatively mild tem- peratures (120 to 130 °C), releasing hexoses and pentoses [6]. The economic feasibility of second-generation ethanol de- pends, among other factors, on the complete conversion of sugars during fermentation and to the cell tolerance to toxic compounds, which are produced during biomass hydrolysis. Saccharomyces cerevisiae is the most efficient yeast for etha- nol production; however, it cannot assimilate pentoses, includ- ing xylose, that is present in high amounts in lignocellulosic hydrolysates [4]. Therefore, the search for efficient pentose- fermenting yeasts has been widely reported on the literature * Marco Antônio Záchia Ayub mazayub@ufrgs.br 1 Biotechnology & Biochemical Engineering Laboratory (BiotecLab), Federal University of Rio Grande do Sul, Av. Bento Gonçalves 9500, PO Box 15090, Porto Alegre, Rio Grande do Sul ZC 91501-970, Brazil 2 Interdepartmental Research Group in Metabolic Engineering, Federal University of Pernambuco, Av. Moraes Rego, 1235, Cidade Universitária, Recife, Pernambuco 50670-901, Brazil 3 Department of Genetics, Federal University of Pernambuco, Av. Moraes Rego, 1235, Cidade Universitária, Recife, Pernambuco 50670-901, Brazil Biomass Conv. Bioref. (2017) 7:199–206 DOI 10.1007/s13399-016-0224-8