Optimization of Process Conditions Using Response Surface Methodology (RSM) for Ethanol Production from Pretreated Sugar
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Optimization of Process Conditions Using Response Surface Methodology (RSM) for Ethanol Production from Pretreated Sugarcane Bagasse: Kinetics and Modeling Ezhumalai Sasikumar & Thangavelu Viruthagiri
Published online: 19 September 2008 # Springer Science + Business Media, LLC. 2008
Abstract Based on a five level central composite design (CCD) involving the variables substrate concentration (C), pH (P), incubation temperature (T) and fermentation time (H), a response surface methodology (RSM) for the production of ethanol from pretreated sugarcane bagasse by cellulase and yeast Kluyveromyces fragilis was standardized. The design contains a total of 31 experimental trials in which the first 24 organized in a factorial design and from 25 to 31 involving the replications of the central points. Data obtained from RSM on ethanol production were subjected to the analysis of variance (ANOVA) and analyzed using a second order polynomial equation. Maximum ethanol concentration (32.6 g/l) was obtained from 180 g/l pretreated sugarcane bagasse at the optimized process conditions (temperature 35°C, pH 5.5) in 72 h aerobic batch fermentation. Various kinetic models such as logistic model, logistic incorporated leudeking piret model and logistic incorporated modified leudeking piret model have been evaluated and the constants were predicted. Keywords Ethanol . Central composite design (CCD) . Response surface methodology (RSM) . Pretreated sugarcane bagasse . Kluyveromyces fragilis
Introduction Over the last century, energy consumption has increased progressively as the result of growing world population and E. Sasikumar (*) : T. Viruthagiri Bioprocess Engineering Research Laboratory, Department of Technology, Annamalai University, Annamalai Nagar 608 002, India e-mail: [email protected]
industrialization. Ethanol is a renewable energy source produced through fermentation of sugars unlike the fossil fuels. Interest in the bioconversion of abundant and renewable cellulosic biomass into fuel ethanol as an alternative to petroleum is rising around the world owing to the realization of diminishing natural oil and gas resources [20]. Lignocellulosic biomass, such as agricultural residues (corn stover, wheat straw, sugarcane bagasse), wood and energy crops, is an attractive material for bioethanol (biomass ethanol) fuel production since it is the most abundant renewable resource on the earth [38]. Lignocellulosic biomass could produce up to 442 billion liters per year of bioethanol [5]. Lignocellulosic materials constitute an abundant and cheap feedstock, but the processing technique required for ethanol production are presently extensive and costly. The cost of ethanol produced from lignocellulosic materials with currently available technology and under the present economic conditions is not competitive with the cost of gasoline [11]. Comprehensive process development and optimization are still required to make the process economically viable. In reality, environmental considerations and energy and tax policies will determ
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