Evaluation of triticale bran as raw material for bioethanol production María García-Aparicio a,⇑ , Kim Trollope a , Luvuyo Tyhoda b , Danie Diedericks a , Johann Görgens a a Department of Process Engineering, Stellenbosch University, Private Bag X1, Stellenbosch 7602, South Africa b Department of Forest and Wood Science, Stellenbosch University, Private Bag X1, Stellenbosch 7602, South Africa article info Article history: Received 2 August 2010 Received in revised form 12 October 2010 Accepted 27 October 2010 Available online 11 November 2010 Keywords: Cereal bran Starch Pretreatment Enzymatic hydrolysis Bioethanol abstract The present work addresses the introduction of second generation biofuels from agricultural by-products generated from low input cereal crops such as triticale. The main purpose was to investigate whether the overall ethanol yield in a triticale dry-mill ethanol plant could be increased by combination of pretreat- ment and enzymatic hydrolysis of the bran obtained by fractionation of the grain to separate from starch. Different dilute acid pretreatment conditions were studied using starch-free triticale bran (SFTB) as sub- strate at a fixed loading of 10% (dry weight/volume). A statistically experimental design approach, based on previous studies, was used to evaluate the sugar recovery so as to maximize the enzyme digestibility of the pretreated material. The highest overall sugar yield was attained by using 0.1% (w/v) of sulphuric acid at 160 °C for 22.5 min. At these conditions, it could be possible to obtain up to 245 L of ethanol per dry ton of SFTB considering hexose and pentose sugars fermentation, which would increase by 14% the theoretical ethanol yield in a dry-mill ethanol plant. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Liquid biofuels, such as ethanol, obtained from plant biomass are regarded as an attractive alternative to fuel oil to reduce depen- dence on foreign oil and diminish CO 2 emissions, the main cause of greenhouse effect. In addition, plant biomass represents the basis for future supply of renewable chemicals and materials [1,2]. Con- sequently, South Africa is making efforts to support the production and use of biofuels in the transport sector. Concretely the short- term goal is the replacement of a 2% in the national liquid fuel sup- ply [3]. In order to reach the goals and the envisioned growth of biofu- els during the next decades, it is essential to extend the raw mate- rials sources to less expensive crops [4]. Novel dedicated crops with high productivity that are well adapted to the climatic and soils conditions are also critical. Triticale, a hybrid of rye and wheat, has been grown commercially in South Africa for the last two decades. Triticale has a number of potential advantages as a feedstock due to its ability to adapt to stresses and thrive on marginal soils with a lower nitrogen requirement during crop growth [5]. To meet the increasing demand for ethanol it is essential not only to select a suitable raw material but also to use it more effi- ciently by the utilization of the whole crop, including lignocellu- losic residues [6]. Cereal bran is produced as by-product of the milling process and it can account for up to 19% of the grain [7]. Cereal bran usually ends up in the distillers dried grain with solu- bles (DDGS), that is used as feed supplement limited to cattle due to its high fiber content [8]. The removal of bran from grain during the cortication stage would reduce the fiber content of the DDGS, and thereby increase the protein content up to 60–65% [9]. This will expand the application of DDGS to other livestock and sub- stantially increase its commercial value [10]. Taking advantage of the installed capacities and existing logistics of the present grain- to-ethanol first generation biofuels pathway can be a winning strategy to gradually introduce second generation biofuels. The bran contains a significant amount of sugars [11–15], such as resid- ual starch, cellulose and hemicellulose, which could be converted to ethanol and enhance production efficiency of the production plant. Among depolymerization processes, those based on enzymatic hydrolysis seem to be promising, due to their specificity and their high potential for improvement by means of biotechnology. The residual starch of the bran can be directly hydrolyzed by amylases. Nonetheless, pretreatment is required to alter the lignocellulose structure in order to improve enzyme accessibility and increase the yield of fermentable sugars. There are various methods which have been reported in literature that can be used to pretreat ligno- cellulosic biomass. These are divided into physical and chemical methods or combination of both [16]. Dilute acid hydrolysis is one of the most commonly applied methods among chemical pre- treatments [17] since it allows the recovery of a high proportion of hemicellulosic sugars without generating significant concentra- tions of inhibitors [18]. It has also been shown to increase the rate of enzymatic hydrolysis considerably [19]. Hemicelluloses, mainly 0016-2361/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.fuel.2010.10.049 ⇑ Corresponding author. Tel.: +27 021 808 4496; fax: +27 021 808 2050. E-mail address: garcia@sun.ac.za (M. García-Aparicio). Fuel 90 (2011) 1638–1644 Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel