Ethanol production and the cost of fermentable sugars from biomass
ABSTRACT The current fermentation alcohol industry in the US is based on utilization of glucose and/or starch derived principally from corn. Biomass materials including wood and agricultural residues, newspaper, and other sources of cellulose could provide a source of fermentable sugars for expanding fuel ethanol production. Prospects for the utilization of biomass for conversion to fermentable hexoses and pentoses are continually improving with advances in enzyme technology, specially engineered microorganisms which can ferment pentoses, and improvement in cellulose pretreatments. Technical and economic factors which affect utilization of sugars from biomass are summarized, and the key steps in wet- and dry-milling of corn are described for purposes of comparison. An approach for estimating fermentable sugar costs is presented to gauge the impact of technical improvements on reducing fermentable sugar costs. An analytical framework resulting from this approach facilitates comparison of effects of feedstock costs, by-product credits, differences in technology, and process costs on the cost of fermentable sugars. A systematic strategy for evaluating differences in cost is presented as a tool for making a first comparison of different technologies and feed stock materials for ethanol production. This analysis suggests that fermentable sugars from enzymatic hydrolysis of cellulose must cost no more than 4–5c lb−1 (8·8–11c kg−1), at current conditions, if they are to be economically competitive with fermentable sugars derived from corn.
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ABSTRACT: A new mild alkaline/oxidative pretreatment of wheat straw prior to enzymic hydrolysis was carried out. It consists of a first alkaline (1% NaOH for 24 h) step, which mainly solubilises hemicellullose and renders the material more accessible to further chemical attack, and a second alkaline/oxidative step (1% NaOH and 0·3% H2O2 for 24 h), which solubilises and oxidises lignin to minor polluting compounds. The entire process was carried out at low temperature (25–40°C) using a low concentration of chemicals, resulting in a relatively low cost and waste liquors containing only trace amounts of dangerous pollutants derived from lignin. Recovery of cellulose after the double pretreatment reached 90% of that contained in the starting material, with a concomitant 81% degradation of lignin. The action of a commercial cellulase on the cellulose obtained produced a syrup with a high concentration of reducing sugars (220 mg/ml), of which a large percentage was glucose.Process Biochemistry 01/1997; 32(8). · 2.52 Impact Factor
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ABSTRACT: BACKGROUND: Production of bioethanol from wood using concentrated acid hydrolysis has received less attention than the dilute acid hydrolysis route. The feasibility of producing lignocellulosic bioethanol from spruce and birch via concentrated acid hydrolysis was studied experimentally. Hydrolysis with sulfuric acid, chromatographic purification of the hydrolysate, and fermentation of the monosaccharides were investigated.RESULTS: Monosaccharide yields of 70% were obtained in the hydrolysis of spruce and birch. Only low amounts of by-products were formed. With chromatographic purification of the hydrolysate, over 90% of the hydrolysis acid was recovered for recycling, and furfural and HMF were removed completely. Most of the acetic acid was recovered in a separate fraction. The monosaccharide yield in a single pass separation was approximately 70%. In the fermentation, S. cerevisiae produced higher amounts of ethanol and more efficiently than P. stipitis. Chromatographically purified hydrolysates gave higher ethanol productivities and yields than Ca(OH)2 neutralized hydrolysates.CONCLUSIONS: Chromatographic purification of concentrated acid lignocellulosic hydrolysates has advantages when compared with neutralization with Ca(OH)2. With chromatography, most of the inhibitory compounds can be removed from the hydrolysates. In addition, due to the recycling of the hydrolysis acid, the economy of the bioethanol manufacturing process is increased considerably. Copyright © 2011 Society of Chemical IndustryJournal of Chemical Technology & Biotechnology 05/2012; 87(5). · 2.50 Impact Factor
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ABSTRACT: Arabinose is considered as an ideal feedstock for the microbial production of value-added chemicals due to its abundance in hemicellulosic wastes. In this study, the araBAD operon from Escherichia coli was introduced into succinate-producing Corynebacterium glutamicum, which enabled aerobic production of succinate using arabinose as sole carbon source. The engineered strain ZX1 (pXaraBAD, pEacsAgltA) produced 74.4mM succinate with a yield of 0.58mol (molarabinose)(-1), which represented 69.9% of the theoretically maximal yield. Moreover, this strain produced 110.2mM succinate using combined substrates of glucose and arabinose. To date, this is the highest succinate production under aerobic conditions in minimal medium.Bioresource Technology 10/2013; · 5.04 Impact Factor