Journal of Biotechnology 125 (2006) 377–384 In situ detoxification and continuous cultivation of dilute-acid hydrolyzate to ethanol by encapsulated S. cerevisiae Farid Talebnia a,b,∗ , Mohammad J. Taherzadeh a a School of Engineering, University College of Bor˚ as, 501 90 Bor ˚ as, Sweden b Department of Chemical Engineering and Environmental Science, Chalmers University of Technology, 412 96 G¨ oteborg, Sweden Received 7 September 2005; received in revised form 28 February 2006; accepted 13 March 2006 Abstract Dilute-acid lignocellulosic hydrolyzate was successfully fermented to ethanol by encapsulated Saccharomyces cerevisiae at dilution rates up to 0.5 h -1 . The hydrolyzate was so toxic that freely suspended yeast cells could ferment it continuously just up to dilution rate 0.1 h -1 , where the cells lost 75% of their viability measured by colony forming unit (CFU). However, encapsulation increased their capacity for in situ detoxification of the hydrolyzate and protected the cells against the inhibitors present in the hydrolyzate. While the cells were encapsulated, they could successfully ferment the hydrolyzate at tested dilution rates 0.1–0.5 h -1 , and keep more than 75% cell viability in the worst conditions. They produced ethanol with yield 0.44 ± 0.01 g/g and specific productivity 0.14–0.17 g/(g h) at all dilution rates. Glycerol was the main by-product of the cultivations, which yielded 0.039–0.052 g/g. HMF present in the hydrolyzate was converted 48–71% by the encapsulated yeast, while furfural was totally converted at dilution rates 0.1 and 0.2 h -1 and partly at the higher rates. Continuous cultivation of encapsulated yeast was also investigated on glucose in synthetic medium up to dilution rate 1.0 h -1 . At this highest rate, ethanol and glycerol were also the major products with yields 0.43 and 0.076g/g, respectively. The experiments lasted for 18–21 days, and no damage in the capsules was detected. © 2006 Elsevier B.V. All rights reserved. Keywords: Encapsulation; S. cerevisiae; Ethanol; In situ detoxification; Dilute-acid hydrolyzate 1. Introduction The low price and abundance of lignocellulosic materials are two of the important factors encouraging ∗ Corresponding author. Tel.: +46 33 435 4429; fax: +46 33 435 4008. E-mail address: farid.talebnia@hb.se (F. Talebnia). research and development for converting lignocellu- lose to fuel ethanol in the last few decades. The pretreat- ment and acid/enzymatic hydrolysis of these materials result in some inhibitors including furans, carboxylic acids and phenolic compounds, which make the culti- vation complicated (Chung and Lee, 1985; Clark and Mackie, 1984; Larsson et al., 1999; Palmqvist and Hahn-H¨ agerdal, 2000). Dilute-acid hydrolysis is a sim- 0168-1656/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jbiotec.2006.03.013