Ethanol production from bread residues |
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| Authors: | Fatemeh Ebrahimi Morteza Khanahmadi Shapoor Roodpeyma Mohammad J. Taherzadeh |
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| Affiliation: | aChemical Engineering Department, Isfahan University of Technology, Isfahan, Iran;bAgricultural Engineering Research Department, Isfahan Center for the Research of Agricultural Science & Natural Resources, Isfahan, Iran;cSchool of Engineering, University of Borås, SE-50190 Borås, Sweden |
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| Abstract: | Bread residues were converted into a suitable fermentation feed via a two-step starch hydrolysis using amylolytic enzymes. Wheat flour hydrolysis was also carried out at the same conditions for comparison. For the first stage, namely liquefaction, effects of temperature (50–85 °C) and substrate concentration (20% and 35%) were investigated. The 3-h liquefaction of the 20% bread suspension made 70% of initial dry matter soluble regardless of the temperature. The liquefaction of the 35% bread suspension had to be carried out by a fed-batch method due to the pasty behavior of the suspension. It resulted in a 65% dissolution of the suspended bread at 85 °C. Saccharification of the latter product led to a fermentation feedstock having a dextrose equivalent (DE) of more than 95 and almost 80% dissolution of the initial dry matter. The prepared feedstock was then cultivated using Saccharomyces cerevisiae, which resulted in an overall yield of 350 g ethanol per kg of initial bread dry matter. Staling of the bread for a week had no effect on liquefaction, saccharification and ethanol yield. |
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| Keywords: | Bread residues Ethanol Hydrolysis α -Amylase Starch Amyloglucosidase |
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