International Review of Chemical Engineering (I.RE.CH.E.), Vol. 4, N. 1 ISSN 2035-1755 January 2012 Special Section on 3 rd CEAM 2011 - Virtual Forum Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved 84 Jerusalem Artichoke and Pea Hulls Based Substrates as Raw Material for Ethanol Production by Saccharomyces cerevisiae Petya Gencheva 1 , Georgi Dobrev 2 , Naiden Delchev 3 , Jordan Hristov 4 , Viara Ivanova 1 Abstract – Jerusalem artichoke flours from tubers and stalks were subjected to jet steam pre- treatment followed by complete inulin hydrolysis. Almost all cellulose in the tubers and more than 80% in the stalks were also hydrolysed. Hydrolysed tuber and stalk flours and pre-treated mash have been found to be effective for alcoholic fermentation with the yeast Saccharomyces cerevisiae and resulted in complete consumption of the fermentable sugars in a 24 hours reaction. The conversion efficiency was 95%. Without jet steam advance treating, the cellulose only in the coarse fraction of the pea hulls flour was partially hydrolysed. After jet steam pre-treatment the hydrolysed cellulose was no more than 10%. Better results were obtained after 0.1M NaOH thermal treatment - approx. 60% of the cellulose was hydrolysed to monosaccharides, most of them fermentable. Thermal pre-treatment with 1.0M H 2 SO 4 resulted in increase of pentose content. The sugar composition affected the alcoholic fermentation activity of the yeasts and the lag-phase augmented to 16 hours, and the entire process to 48 hours. Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved. Keywords: Ethanol, Saccharomyces Cerevisiae, Inulin, Pea Hulls, Hydrolysis, Fermentation I. Introduction The most common renewable fuel today and suitable alternative to replace fossil fuels is ethanol that can be blended with petrol or used as neat alcohol in engines. Ethanol is currently produced from sugar (Brazil) or grain (starch, USA) – in the so-called “first generation process” of ethanol production [1]-[2]. However, this raw material base will not be sufficient because the increasing demand for fuel ethanol and the lower than expected reduction of greenhouse gases. The cost of raw material dominates the cost of total ethanol production. To attain commercial interest, the cost of bioethanol production must be reduced, and a sufficient amount of cheap and readily available raw material is a necessity [3]. An alternative is the production of bioethanol from agro-industrial wastes or from plants that can be grown on marginal land such as the Jerusalem artichoke (topinambour). Like sugar beet, the topinambour produces sugars (mainly inulin) in above ground stalks and stores them in roots and tubers at end of harvesting season. The pea hulls, a by-product of the industrial dehulling of pea seeds, contain approx. 8.0 mg/g dry matter free sugars, sucrose – 5.0-15.0 mg/g, starch – 8.0- 17.0 mg/g, total carbohydrates - approx. 800 mg/g dry matter and 450 mg/g cellulose [4]. Inulin is a polyfructan and an energy reserve in the roots and tubers of plants and consists of linear chains of fructose residues linked by β-(2→1)-bonds and terminated by a glucose residue. In general, plant inulins contain between 20 and several thousand fructose units. Inulin is sometimes categorized as a prebiotic and can be used to replace sugar, fat, and flour. The inulin containing Jerusalem artichoke (topinambour) (Helianthus tuberosus L.) is attractive carbohydrate source for ethanol and biogas [5], as well as for inulin containing functional foods production. Jerusalem artichoke have some advantages to other agricultural sources of carbohydrates because it growth on poor soil, is tolerant to low temperature and demands low amounts of fertilizers. In the topinambour sugars are stored in the stalks before the rapid transfer to tubers in late September. Using the stalks and the tubers as the raw material for sugar makes the process more economically appropriate. Thus, a second generation ethanol production from cellulosic materials could be combined with the first generation process of ethanol production from Jerusalem artichoke soluble sugars (inulin, fructose, glucose). Nonhydrolyzed inulin can be directly converted to ethanol in a simultaneous saccharification and fermentation process [6]. Jerusalem artichoke mash, juice or flour can be used as media for ethanol production when fermented by microorganisms such as: Saccharomyces cerevisiae [7], Zymomonas mobilis [8], Aspergillus niger [9]-[10], Kluyveromyces marxianus, Kluyveromyces fragilis [11]-[12], Pichia [13]. The potential application of Jerusalem artichoke extracts for bioethanol production was studied at first by Margaritis et al. [14]. The acid and enzymatic hydrolysis