PEER-REVIEWED ARTICLE bioresources.com Millati et al. (2008). “Ethanol from wood hydrolyzate,” BioResources 3(4), 1020-1029. 1020 ETHANOL PRODUCTION FROM XYLOSE AND WOOD HYDROLYZATE BY MUCOR INDICUS AT DIFFERENT AERATION RATES Ria Millati a,d* , Keikhosro Karimi b,d , Lars Edebo c , Claes Niklasson d , and Mohammad J. Taherzadeh e The fungus Mucor indicus is able to produce ethanol from xylose as well as dilute-acid lignocellulosic hydrolyzates. The fungus completely assimilated 10 g/L xylose as the sole carbon and energy source within 32 to 65 h at an aeration rate of 0.1 to 1.0 vvm. The highest ethanol yield was 0.16 g/g at 0.1 vvm. Xylitol was formed intermediately with a maximum yield of 0.22 g/g at 0.5 vvm, but disappeared towards the end of experiments. During cultivation in a mixture of xylose and glucose, the fungus did not assimilate xylose as long as glucose was present in the medium. The anaerobic cultivation of the fungus in the hydrolyzate containing 20% xylose and 80% hexoses resulted in no assimilation of xylose but complete consumption of the hexoses in less than 15 h. The ethanol yield was 0.44 g/g. However, the xylose in the hydrolyzate was consumed when the media was aerated at 0.067 to 0.333 vvm. The best ethanol yield was 0.44 g/g at 0.067 vvm. The results of this study suggest that M. indicus hydrolyzate can be first fermented anaerobically for hexose assimilation and subsequently continued under oxygen- limited conditions for xylose fermentation. Keywords: Ethanol; lignocellulosic hydrolyzate; Xylose; Mucor indicus; Xylitol; Aeration rate Contact information: a: Food and Agricultural Product Technology Department, Gadjah Mada University, Yogyakarta, Indonesia; b: Chemical Engineering Department; Isfahan University of Technology, Isfahan, 84156-83111, Iran; c: Clinical Bacteriology Department, Göteborg University, S- 413 46 Göteborg, Sweden; d: Chemical Reaction Engineering, Chalmers University of Technology, S-412 96, Göteborg, Sweden; e: School of Engineering, University of Borås, S-501 90, Borås, Sweden; *Corresponding author: ria_millati@yahoo.com INTRODUCTION The turbulences in the oil market during the last four decades and the global desire to reduce net CO 2 emission has made ethanol a desirable fuel (Taherzadeh and Karimi 2007). Sugars and grains are the dominant feedstocks for ethanol production, but lignocellulosic biomass is considered as the key feedstock in the future. Lignocellulosic biomass contains cellulose, hemicellulose, and lignin. Glucose, which is the sugar monomer of cellulose, is preferentially fermented by most microorganisms, including baker’s yeast Saccharomyces cerevisiae. However, this yeast cannot assimilate xylose, which comprises 15-40% of sugar monomers in hardwoods and typical agricultural crop residues (Potera 2004; Sun and Cheng 2002). The fungus Mucor indicus (formerly Mucor rouxii) has recently been revealed as an alternative microorganism to S. cerevisiae with capability of utilizing both hexoses