Available online at www.sciencedirect.com ScienceDirect BIORESOURCE TECHn○LOGY ELSEVIER Bioresource Technology99(2008)847-854 Impacts of main factors on bioethanol fermentation from stalk juice of sweet sorghum by immobilized Saccharomyces cerevisiae (CICC 1308) Ronghou Liu *Fei Shen Biomass Energy Engineering Research Centre.School of Agriculture and Biology.Shanghai JiaoTong University.2678 Qi Xin Road. Shanghai 201101,PR China Received 17 October 2006;received in revised form 17 January 2007;accepted 17 January 2007 Available online 13 March 2007 Abstract In order to attain a higher ethanol yield and faster ethanol fermentation rate,orthogonal experiments of ethanol fermentation with immobilized yeast from stalk juice of sweet sorghum were carried out in the shaking flasks to investigate the effect of main factors namely,fermentation temperature,agitation rate,particles stuffing rate and pH on ethanol yield and COz weight loss rate.The range analysis and analysis of variance(ANOVA)were applied for the results of orthogonal experiments.Results showed that the optimal con- dition for bioethanol fermentation should be A B,C,D,namely,fermentation temperature,agitation rate,particles stuffing rate and pH were 37C,200rpm,25%and 5.0,respectively.The verification experiments were carried out in shaking flasks and 5L bioreactor at the corresponding parameters.The results of verification experiments in the shaking flasks showed that ethanol yield and CO,weight loss rate were 98.07%and 1.020gh,respectively.The results of ethanol fermentation in the 5L bioreactor showed that ethanol yield and fer- mentation time were 93.24%and 11 h,respectively.As a result,it could be concluded that the determined optimal condition A BC3D was suitable and reasonable for the ethanol fermentation by immobilized Saccharomyces cerevisiae.The conclusion in the research would be beneficial for application of ethanol fermentation by immobilized S.cerevisiae from stalk juice of sweet sorghum. 2007 Elsevier Ltd.All rights reserved. Keywords:Suitable parameters;Sweet sorghum;Immobilized Saccharomyces cerevisiae;Bioethanol fermentation 1.Introduction malt or molds.Cellulose (from wood,agricultural residues, waste sulfite liquor from pulp,and paper mills)must like- Ethanol production as an alternative fuel energy wise be converted into sugars,generally by the action of resource has been a subject of great interest since the oil cri- mineral acids.Once simple sugars are formed,enzymes sis of the 1970s (Tao et al,2005).Therefore,a strong need from microorganisms can readily ferment them to ethanol exists for efficient ethanol production with low cost in raw (Lin and Tanaka,2006).As for materials,one of the prime material and production process.The varied raw materials sources being investigated for ethanol is sweet sorghum. used in the production of ethanol via fermentation are con- Sweet sorghum {Sorghim biocolor (L.)Moench is a high veniently classified into three main types of raw materials: biomass-and sugar-yielding crops (Bryan,1990),mean- sugars,starches,and cellulose materials.Sugars(from sug- time,the stalk of sweet sorghum contains quite a few quan- arcane,sugar beets,sweet sorghum.molasses,and fruits) tities of soluble (glucose and sucrose)and insoluble can be converted into ethanol directly.Starches(from corn, carbohydrates (cellulose and hemicellulose)(Jasberg et al., cassava,potatoes,and root crops)must firstly be hydro- 1983).Therefore,of many crops currently being investi- lyzed to fermentable sugars by the action of enzymes from gated for energy and industry,sweet sorghum is one of the most promising,particularly for ethanol production (Gnansounou et al.,2005). Corresponding author.Tel:+862164783844:fax:+8621 64193285. The advantages of immobilized cells over free cell sys- E-mail address:liurhou@sjtu.edu.cn (R.Liu). tems have been extensively reported (Plessas et al.,2007). 0960-8524/S-see front matter 2007 Elsevier Ltd.All rights reserved. doi:10.1016f.biortech.2007.01.009Bioresource Technology 99 (2008) 847–854 0960-8524/$ - see front matter © 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2007.01.009 Available online at www.sciencedirect.com Impacts of main factors on bioethanol fermentation from stalk juice of sweet sorghum by immobilized Saccharomyces cerevisiae (CICC 1308) Ronghou Liu ¤ , Fei Shen Biomass Energy Engineering Research Centre, School of Agriculture and Biology, Shanghai JiaoTong University, 2678 Qi Xin Road, Shanghai 201101, PR China Received 17 October 2006; received in revised form 17 January 2007; accepted 17 January 2007 Available online 13 March 2007 Abstract In order to attain a higher ethanol yield and faster ethanol fermentation rate, orthogonal experiments of ethanol fermentation with immobilized yeast from stalk juice of sweet sorghum were carried out in the shaking Xasks to investigate the eVect of main factors, namely, fermentation temperature, agitation rate, particles stuYng rate and pH on ethanol yield and CO2 weight loss rate. The range analysis and analysis of variance (ANOVA) were applied for the results of orthogonal experiments. Results showed that the optimal con￾dition for bioethanol fermentation should be A4B3C3D4, namely, fermentation temperature, agitation rate, particles stuYng rate and pH were 37 °C, 200 rpm, 25% and 5.0, respectively. The veriWcation experiments were carried out in shaking Xasks and 5 L bioreactor at the corresponding parameters. The results of veriWcation experiments in the shaking Xasks showed that ethanol yield and CO2 weight loss rate were 98.07% and 1.020 g h¡1 , respectively. The results of ethanol fermentation in the 5 L bioreactor showed that ethanol yield and fer￾mentation time were 93.24% and 11 h, respectively. As a result, it could be concluded that the determined optimal condition A4B3C3D4 was suitable and reasonable for the ethanol fermentation by immobilized Saccharomyces cerevisiae. The conclusion in the research would be beneWcial for application of ethanol fermentation by immobilized S. cerevisiae from stalk juice of sweet sorghum. © 2007 Elsevier Ltd. All rights reserved. Keywords: Suitable parameters; Sweet sorghum; Immobilized Saccharomyces cerevisiae; Bioethanol fermentation 1. Introduction Ethanol production as an alternative fuel energy resource has been a subject of great interest since the oil cri￾sis of the 1970s (Tao et al., 2005). Therefore, a strong need exists for eYcient ethanol production with low cost in raw material and production process. The varied raw materials used in the production of ethanol via fermentation are con￾veniently classiWed into three main types of raw materials: sugars, starches, and cellulose materials. Sugars (from sug￾arcane, sugar beets, sweet sorghum, molasses, and fruits) can be converted into ethanol directly. Starches (from corn, cassava, potatoes, and root crops) must Wrstly be hydro￾lyzed to fermentable sugars by the action of enzymes from malt or molds. Cellulose (from wood, agricultural residues, waste sulWte liquor from pulp, and paper mills) must like￾wise be converted into sugars, generally by the action of mineral acids. Once simple sugars are formed, enzymes from microorganisms can readily ferment them to ethanol (Lin and Tanaka, 2006). As for materials, one of the prime sources being investigated for ethanol is sweet sorghum. Sweet sorghum {Sorghum biocolor (L.) Moench} is a high biomass- and sugar-yielding crops (Bryan, 1990), mean￾time, the stalk of sweet sorghum contains quite a few quan￾tities of soluble (glucose and sucrose) and insoluble carbohydrates (cellulose and hemicellulose) (Jasberg et al., 1983). Therefore, of many crops currently being investi￾gated for energy and industry, sweet sorghum is one of the most promising, particularly for ethanol production (Gnansounou et al., 2005). The advantages of immobilized cells over free cell sys￾tems have been extensively reported (Plessas et al., 2007). * Corresponding author. Tel.: +86 21 64783844; fax: +86 21 64193285. E-mail address: liurhou@sjtu.edu.cn (R. Liu)