The effect of microwave (MW)-assisted acid or alkali pretreatment (300 W, 7 min) followed by saccharification with a triple enzyme cocktail (Cellic, Optimash BG and Stargen) with or without detoxification mix on ethanol production from three cassava residues (stems, leaves and peels) by Saccharomyces cerevisiae was investigated. Significantly higher fermentable sugar yields (54.58, 47.39 and 64.06 g/L from stems, leaves and peels, respectively) were obtained after 120 h saccharification from MW-assisted alkali-pretreated systems supplemented (D+) with detoxification chemicals (Tween 20 + polyethylene glycol 4000 + sodium borohydride) compared to the non-supplemented (D0) or MW-assisted acid-pretreated systems. The percentage utilization of reducing sugars during fermentation (48 h) was also the highest (91.02, 87.16 and 89.71%, respectively, for stems, leaves and peels) for the MW-assisted alkali-pretreated (D+) systems. HPLC sugar profile indicated that glucose was the predominant monosaccharide in the hydrolysates from this system. Highest ethanol yields (YE, g/g), fermentation efficiency (%) and volumetric ethanol productivity (g/L/h) of 0.401, 78.49 and 0.449 (stems), 0.397, 77.71 and 0.341 (leaves) and 0.433, 84.65 and 0.518 (peels) were also obtained for this system. The highest ethanol yields (ml/kg dry biomass) of ca. 263, 200 and 303, respectively, for stems, leaves and peels from the MW-assisted alkali pretreatment (D+) indicated that this was the most effective pretreatment for cassava residues.
This is a preview of subscription content, log in to check access.
The first author gratefully acknowledges the research fellowship granted for the study by the Kerala State Council for Science, Technology and Environment (KSCSTE), Govt. of Kerala. Authors are thankful to the Director, ICAR-CTCRI for the facilities provided for the study and Dr. J. Sreekumar, Principal Scientist (Agricultural Statistics), ICAR-CTCRI for the help extended in statistical analyses. The support extended for the HPLC analyses by Dr. A. N. Jyothi, Principal Scientist and Mr. V. R. Vishnu, Senior Research Fellow, ICAR-CTCRI is also thankfully acknowledged.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
Ahamefule FO (2005) Evaluation of pigeon pea-cassava peel based diets for goat production in South-Eastern Nigeria. Ph.D. Thesis, Michael Okpara University of Agriculture, UmudikeGoogle Scholar
Alkasrawi M, Eriksson T, Borjesson J, Wingren A, Galbe M, Tjerneld F, Zacchi G (2003) The effect of Tween-20 on simultaneous saccharification and fermentation of softwood to ethanol. Enzyme Microb Technol 33:71–78CrossRefGoogle Scholar
Anon (2009a) STARGEN™002: Granular starch hydrolyzing enzyme for ethanol production. Product information published by Genencor International, a Division of Danisco, Danisco US Inc. http://www.genencor.com. 22 Dec 2014
Anon (2009b) OPTIMASH™BG and OPTIMASH™XL: Product information published by Genencor International, a division of Danisco. http://www.genencor.com. Accessed 26 Nov 2015
AOAC (2005) Official methods of analysis of AOAC international, 18th edn. Horwitz W, Latimer GW (eds.)Google Scholar
Barcelos CA, Maeda RN, Betancur GJV, Pereira N Jr (2011) Ethanol production from sorghum grains [Sorghum bicolor (L.) Moench]: evaluation of the enzymatic hydrolysis and the hydrolysate fermentability. Braz J Chem Eng 28(4):597–604CrossRefGoogle Scholar
Buruiana C-T, Garrote G, Vizireanu C (2013) Bioethanol production from residual lignocellulosic materials: a review—Part 2. The annals of the University Dunarea de Jos of Galati Fascicle VI. Food Technol 37(1):25–38Google Scholar
Kongkiattikajorn J (2012) Ethanol production from dilute acid pretreated cassava peel by fed-batch simultaneous saccharification and fermentation. Inter J Computer Internet Management 20:22–27Google Scholar
Kongkiattikajorn J, Sornvoraweat B (2011) Comparative study of bioethanol production from cassava peels by monoculture and co-culture of yeast. Kasetsart J (Nat Sci) 45:268–274Google Scholar
Maurya DP, Vats S, Rai S, Negi S (2013) Optimization of enzymatic saccharification of microwave pretreated sugarcane tops through response surface methoD0logy for biofuel. Ind J Exp Biol 51(11):992–996Google Scholar
Merino-Pérez O, Martínez-Palou R, Labidi J, Luque R (2015) Microwave-assisted pretreatment of lignocellulosic biomass to produce biofuels and value-added products. In: Fang Z, Smith Jr, Richard L, Qi X (eds) Production of biofuels and chemicals with microwave. Biofuels Biorefin. 3:197–224. https://doi.org/10.1007/978-94-017-9612-5_10
Nelson N (1944) A photometric adaptation of the Somogyi method for determination of glucose. J Biol Chem 153:375–380Google Scholar
Nomanbhay M, Saifuddin Hussain R, Palanisamy K (2013) Microwave-assisted alkaline pretreatment and microwave assisted enzymatic saccharification of oil palm empty fruit bunch fiber for enhanced fermentable sugar yield. J Sustain Bioenergy Syst 3(1):7–17CrossRefGoogle Scholar
Öhgren KH, Hahn B, Zacchi G (2006) Simultaneous saccharification and co- fermentation of glucose and xylose in steam pretreated corn stover at high fiber content with S. cerevisiae. J Biotechnol 126:488–496CrossRefGoogle Scholar
Pooja NS, Padmaja G (2017) Microwave-Assisted alkali delignification coupled with non-Ionic surfactant effect on the fermentable sugar yield from agricultural residues of cassava. Internat J Environ Agric Biotechnol 2(2):1–13. https://doi.org/10.22161/ijeab/2.2.10(ISSN: 2456-1878)Google Scholar
SAS/STAT Software Version 9.3, SAS Institute Inc., Cary, NC, 2010Google Scholar
Singh A, Tuteja S, Singh N, Bishnoi NR (2011) Enhanced saccharification of rice straw and hull by microwave-alkali pretreatment and lignocellulolytic enzyme production. Bioresour Technol 102:1773–1782CrossRefGoogle Scholar
Singh A, Bajar S, Bishnoi NR (2014) Enzymatic hydrolysis of microwave alkali pretreated rice husk for ethanol production by Saccharomyces cerevisiae, Scheffersomyces stipitis and their co-culture. Fuel 116:699–702CrossRefGoogle Scholar