Abstract
BackgroundAs the supply of starch grain and sugar cane, currently the main feedstocks for bioethanol production, become limited, lignocelluloses will be sought as alternative materials for bioethanol production. Production of cellulosic ethanol is still cost-inefficient because of the low final ethanol concentration and the addition of nutrients. We report the use of simultaneous saccharification and cofermentation (SSCF) of lignocellulosic residues from commercial furfural production (furfural residue, FR) and corn kernels to compare different nutritional media. The final ethanol concentration, yield, number of live yeast cells, and yeast-cell death ratio were investigated to evaluate the effectiveness of integrating cellulosic and starch ethanol.ResultsBoth the ethanol yield and number of live yeast cells increased with increasing corn-kernel concentration, whereas the yeast-cell death ratio decreased in SSCF of FR and corn kernels. An ethanol concentration of 73.1 g/L at 120 h, which corresponded to a 101.1% ethanol yield based on FR cellulose and corn starch, was obtained in SSCF of 7.5% FR and 14.5% corn kernels with mineral-salt medium. SSCF could simultaneously convert cellulose into ethanol from both corn kernels and FR, and SSCF ethanol yield was similar between the organic and mineral-salt media.ConclusionsStarch ethanol promotes cellulosic ethanol by providing important nutrients for fermentative organisms, and in turn cellulosic ethanol promotes starch ethanol by providing cellulosic enzymes that convert the cellulosic polysaccharides in starch materials into additional ethanol. It is feasible to produce ethanol in SSCF of FR and corn kernels with mineral-salt medium. It would be cost-efficient to produce ethanol in SSCF of high concentrations of water-insoluble solids of lignocellulosic materials and corn kernels. Compared with prehydrolysis and fed-batch strategy using lignocellulosic materials, addition of starch hydrolysates to cellulosic ethanol production is a more suitable method to improve the final ethanol concentration.
Highlights
As the supply of starch grain and sugar cane, currently the main feedstocks for bioethanol production, become limited, lignocelluloses will be sought as alternative materials for bioethanol production
The overall kinetics were limited by the fermentation step because of the high concentrations of sugars, which were found to be parallel to the concentration of corn kernels at the beginning of simultaneous saccharification and cofermentation (SSCF)
An increase in the concentration of corn kernels lengthened the time it took to deplete the sugars (Figure 1B, C). This was less than 48 h in all cases, which indicated that, for corn kernels, SSCF was as productive as simultaneous saccharification and fermentation (SSF)
Summary
As the supply of starch grain and sugar cane, currently the main feedstocks for bioethanol production, become limited, lignocelluloses will be sought as alternative materials for bioethanol production. Starch and sugars from existing food crops are the main feedstocks for bioethanol production, because they are easy to use and cost-efficient [2]; it is expected that. Recycled paper sludge can be used for the production of ethanol or other chemicals without being pretreated for bioconversion, because the paper raw materials already undergo extensive processing during the paper-making process [12]. Another example is furfural residue (FR), an industrial waste in China. Ethanol production from FR would reduce environmental pollution, and efficiently use the corncob material [13]. Detoxification is necessary for ethanol production from FR, and rinsing with water has been proven to be an effective detoxifying method [14]
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