Short Communication Optimization study of ethanolic fermentation from oil palm trunk, rubberwood and mixed hardwood hydrolysates using Saccharomyces cerevisiae K.L. Chin a, * , P.S. H’ng a , L.J. Wong a , B.T. Tey b , M.T. Paridah c a Faculty of Forestry, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia b Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia c Institute of Tropical Forestry and Forest Product, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia article info Article history: Received 3 October 2009 Received in revised form 6 December 2009 Accepted 10 December 2009 Available online 6 January 2010 Keywords: Lignocelulosic biomass Ethanol yield Fermentation time Fermentation efficiency abstract Ethanolic fermentation using Saccharomyces cerevisiae was carried out on three types of hydrolysates pro- duced from lignocelulosic biomass which are commonly found in Malaysia such as oil palm trunk, rub- berwood and mixed hardwood. The effect of fermentation temperature and pH of hydrolysate was evaluated to optimize the fermentation efficiency which defined as maximum ethanol yield in minimum fermentation time. The fermentation process using different temperature of 25 °C, 30 °C and 40 °C were performed on the prepared fermentation medium adjusted to pH 4, pH 6 and pH 7, respectively. Results showed that the fermentation time was significantly reduced with the increase of temperature but an adverse reduction in ethanol yield was observed using temperature of 40 °C. As the pH of hydrolysate became more acidic, the ethanol yield increased. Optimum fermentation efficiency for ethanolic fermen- tation of lignocellulosic hydrolysates using S. cerevisiae can be obtained using 33.2 °C and pH 5.3. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction For decades, efforts have been made on increasing the utility of lignocellulosic biomass. In addition to the growing demand for traditional applications such as fiber products, novel markets for lignocellulosic biomass in place of petrochemicals have been iden- tified in recent years (Malherbe and Cloete, 2002). As one of the top producers of palm oil and wooden furniture in the world, Malaysia is well positioned to take advantage of its enormous output of lig- nocellulosic biomass. Recently, researchers have been focusing on the feasibility of these new applications on improving the commer- cial viability of lignocellulosic biomass. The most ambitious con- version of these has been the conversion to alternative energy carriers (e.g. fuel ethanol, acetone and butanol) (Kaylen et al., 2000). Ethanol is widely known to become a sustainable transpor- tation fuel in the near future (Thomsen et al., 2003). Optimal conditions are required to ensure high yield of the fermentation product and shorter fermentation time for cost efficiency of producing ethanol from lignocellulosic biomass. The pH has a significant influence on fermentation due to its effect on yeast growth, fermentation rate and by product formation (Pra- manik, 2003). The fermentation process requires optimum pH conditions as the microorganism that contributes to the fermenta- tion, works best at certain pH. Temperature is also one of the most crucial variables to monitor during the fermentation. Research regarding the influence of temperature on the fermentation has yielded a complex mixture of products. Charoenchai et al. (1998) performed an experiment testing the effect of temperature on the fermentation rate for 22 different strains of yeast. In general, the outcome for all the yeast tested in the experiment indicated that greater temperatures increased growth rates. However, yeast may have behaved differently in different lignocellulosic biomass hydrolysate at different temperatures (Kurtzman and Fell, 2005). Very little is known on how fermentation temperature and pH affect the ethanol fermentation on lignocellulosic hydrolysates (oil palm trunk, rubberwood and mixed hardwood) using Saccha- romyces cerevisiae. Therefore, there is a need to understand and evaluate the effect of fermentation temperature and pH of hydro- lysate on the fermentation efficiency i.e., ethanol yield and fer- mentation time. The appropriate fermentation conditions for rubberwood, mixed hardwood and oil palm hydrolysate can be determined by evaluating the effect of different temperature and pH conditions on the ethanol yield from fermentation process by yeast ( S. cerevisiae). The most efficient ethanol fermentation conditions were determined by high yield of ethanol in the short- est fermentation time. The optimization study of the fermentation parameters; temperature and pH will contribute to high fermen- tation efficiency. 0960-8524/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2009.12.036 * Corresponding author. Tel.: +60 3 8946 7189; fax: +60 3 8943 2514. E-mail address: dwinackl@gmail.com (K.L. Chin). Bioresource Technology 101 (2010) 3287–3291 Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech