Ethanol production from bread residues

✍ Scribed by Fatemeh Ebrahimi; Morteza Khanahmadi; Shapoor Roodpeyma; Mohammad J. Taherzadeh

• Publisher: Elsevier Science
• Year: 2008
• Tongue: English
• Weight: 261 KB
• Volume: 32
• Category: Article
• ISSN: 0961-9534
• DOI: 10.1016/j.biombioe.2007.10.007

✦ Synopsis

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 1C) 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 1C. 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.