Romanian Biotechnological Letters Vol. 16, No. 5, 2011 Copyright © 2011 University of Bucharest Printed in Romania. All rights reserved ORIGINAL PAPER 6497 Bioethanol production from Jerusalem artichoke by acid hydrolysis Received for publication, January 27, 2011 Accepted, September 10, 2011 RADOJKA N. RAZMOVSKI, MARINA B. ŠĆIBAN, VESNA M. VUČUROVIĆ University of Novi Sad, Faculty of Technology, Bulevar Cara Lazara 1, 21000 Novi Sad, Republic of Serbia *Corresponding author: Tel:+381214853736, Fax:+38121450413, e-mail:razmovski@tf.uns.ac.rs Abstract The hydrolysis of inulin from Jerusalem artichoke (JA) slices by HCl under different regimes of temperature and hold (contact time) time was investigated. Final reducing sugars concentration in the hydrolyzates depended on temperature, pH, hydromodule (JA:water) and hold time. Acid hydrolysis at higher temperature and longer hold time increased the degradation of fructan to fructose and increased the concentrations of inhibitory compounds such as 5-hydroxymethylfurfural (HMF). Acid hydrolysis at 126 o C, hydromodule 1:1 and pH 2, resulted in less than 0.2 g/L HMF at both hold times (30 min and 60 min.). Fermentation of the hydrolyzates obtained by hydrolysis at 126 o C, hydromodule 1:1, pH 2 and hold time 60 min, resulted in the highest ethanol yield of 7.6 % w/w, which corresponds to volumetric productivity of ethanol 1.52 g /Lh and 94.12 % (w/w) of theoretical yield of ethanol. Key words: Bioethanol, Jerusalem artichoke, acid hydrolysis, S. cerevisiae Introduction Nowadays, bioethanol produced by alcoholic fermentation is widely used as a renewable biofuel. Main feedstock for ethanol production are sugar cane and corn grain, while many other agricultural raw materials rich in fermentable carbohydrates, or those locally available that could be converted to yield the fermentable sugars, are used worldwide [1]. One major problem with ethanol production is the availability and the price of the raw materials, because feedstock costs account for more than one-third of the final production costs [2]. Feedstock based on corn, sorghum, Jerusalem artichoke, potato and lignocellulosic biomass are of the greatest interest for ethanol production. Jerusalem artichoke (JA) (Helianthus tuberosus L.) tubers represent an alternative feedstock for bioethanol production, because ethanol yield is equivalent to that obtained from sugar beets and twofold that of corn [3]. The tubers accumulate high levels of polysaccharides (fructans) during their growth. On a dry weight basis, the tubers contain 68-83% fructans, 15-16% proteins, 13% insoluble fiber and 5% ash [4]. Inulin is a linear polymer of D-fructose joined by ß (2→1) linkages and terminated with a D-glucose molecule linked to fructose by an α (1→2) bond, as in sucrose. When JA is to be used for ethanol fermentation by Saccharomyces cerevisiae it is first converted to fermentable sugars by enzymes or acid [5]. Kim and Hamdy [6] concluded that JA slurry should be hydrolyzed in 0.1 M HCl at 97°C and than subjected to alcohol fermentation. It was reported that between pH 1 and 2 the extent of dehydration of fructose varied linearly with time and pH but was minimal at pH 2 [7]. Fructan in Helianthus tuberosus can be easily extracted then be hydrolyzed to fructose by acid which is also the first step in dimethylfuran production [8]. Fleming and GrootWassink [4] compared various acids (hydrochloric, sulfuric, citric and phosphoric) for their effectiveness on inulin hydrolysis. The available literature provides little information about the kinetics and efficiency of acid hydrolysis of JA tubers into sugar or about the by-product of hydrolysis such as 5- hydroxymethylfurfural (HMF) which can inhibit the yeast growth and fermentation.