Journal
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
Volume 16, Issue 5, Pages 10650-10664Publisher
MDPI
DOI: 10.3390/ijms160510650
Keywords
biohydrogen; bioethanol; crude glycerol; Enterobacter aerogenes; CSTR
Funding
- Fonds quebecois de la recherche sur la nature et les technologies
- Thailand Institute of Scientific and Technological Research
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Crude glycerol from the biodiesel manufacturing process is being produced in increasing quantities due to the expanding number of biodiesel plants. It has been previously shown that, in batch mode, semi-anaerobic fermentation of crude glycerol by Enterobacter aerogenes can produce biohydrogen and bioethanol simultaneously. The present study demonstrated the possible scaling-up of this process from small batches performed in small bottles to a 3.6-L continuous stir tank reactor (CSTR). Fresh feed rate, liquid recycling, pH, mixing speed, glycerol concentration, and waste recycling were optimized for biohydrogen and bioethanol production. Results confirmed that E. aerogenes uses small amounts of oxygen under semi-anaerobic conditions for growth before using oxygen from decomposable salts, mainly NH4NO3, under anaerobic condition to produce hydrogen and ethanol. The optimal conditions were determined to be 500 rpm, pH 6.4, 18.5 g/L crude glycerol (15 g/L glycerol) and 33% liquid recycling for a fresh feed rate of 0.44 mL/min. Using these optimized conditions, the process ran at a lower media cost than previous studies, was stable after 7 days without further inoculation and resulted in yields of 0.86 mol H-2/mol glycerol and 0.75 mol ethanol/mole glycerol.
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