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Microwave Pretreatment, Enzymatic Saccharification and Fermentation of Wheat Straw to Ethanol

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Wheat straw used in this study contained 38.8±0.5% cellulose and 31.0±0.3% hemicellulose. The effects of temperature (160–240 °C, 5 min) and duration (5–20 min at 200 °C) of microwave pretreatment of wheat straw (8.6%, w/v, in water) on its enzymatic saccharification to fermentable sugars were evaluated. The yield of monomeric sugars from microwave (200 °C, 10 min) pretreated wheat straw (8.6%, w/v, in water) after enzymatic saccharification (45 °C, pH 5.0, 120 h) using a cocktail of 3 commercial enzyme preparations (cellulase, -glucosidase, and hemicellulase) at the dose level of 0.15 ml of each enzyme preparation per g wheat straw was 544±7 mg/g straw (glucose, 320±14 mg; xylose, 189±7 mg; arabinose, 21±1 mg; galactose, 10±0 mg; 70% yield). In addition, the hydrolyzate contained 2.9±1.6 mg furfural, 0.3±0.0 mg hydroxymethyl furfural, and 60±8 mg acetic acid per g of straw. The maximum release of sugars (651±7 mg/g straw, 84% yield) from wheat straw after enzymatic hydrolysis was obtained by microwave pretreatment in dilute acid (0.5% H2SO4, w/v) at 160 °C for 10 min. Microwave pretreatment of wheat straw with lime (0.1 g/g straw) at 160 °C for 10 min released 604±30 mg total sugars/g straw (78% yield) after enzymatic hydrolysis. The concentration of ethanol from microwave pretreated (200 °C, 10 min, in water) and enzyme saccharified (45 °C, pH 5.0, 120 h) wheat straw (78 g/liter) hydrolyzate after overliming by recombinant Escherichia coli strain FBR5 at pH 6.5 and 35 °C in 40 h was 16.8±0.1 g/liter with a yield of 0.49 g/g available sugars (0.22 g/g straw). The ethanol concentration was 16.7±1.5 g/liter with a yield of 0.21 g/g straw in the case of simultaneous saccharification and fermentation of microwave pretreated (200 °C, 10 min, in water) wheat straw (78 g/liter) after overliming by the E. coli strain at pH 6.0 and 35 °C in 69 h.

Keywords: ENZYMATIC SACCHARIFICATION; ETHANOL; MICROWAVE PRETREATMENT; SEPARATE HYDROLYSIS AND FERMENTATION; SIMULTANEOUS SACCHARIFICATION AND FERMENTATION; WHEAT STRAW

Document Type: Research Article

Publication date: 01 September 2008

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  • The goal of the creation of a biobased economy is challenging to agriculture, forestry, academia, government and industry. The extractable resources of the Earth are finite, regardless of the quibble over when they will be depleted. The economic, political and social demands for biobased chemicals, materials and energy are expected to radically transform the materials industries, particularly the plastics industry as well as the biofuel industry. These changes will be based on the principles of sustainability, eco-efficiency, industrial ecology, and green chemistry and engineering. In keeping with the growth of knowledge in this field, there is a strong need for a forum to share original research related to biobased materials and bioenergy. The Journal of Biobased Materials and Bioenergy (JBMB) has been created as an international peer-reviewed periodical to fulfill the need for communication in these research areas. This journal will encompass related research activities in all fields of science, engineering and the life sciences.
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