Hydrogen Production from Crude Glycerol from Biodiesel Production in Repeated Semi-continuous Process by Escherichia coli HB41

บทคัดย่อ

The aim of this work was to study hydrogen production in a semi-continuous process by E. coli HB41 from crude glycerol, the by product or waste from biodiesel production. Hydrogen production from a medium containing 20 g/l glycerol at various feeding rates: 5, 10, 15, 20% of 1 liter working volume by feeding every day for 5 days, was examined. It was found that the highest hydrogen yield at 0.231 mol hydrogen/ mole glycerol was gained at a 5% loading rate. The hydrogen yield at a feeding rate of 10, 15 and 20% was 0.102, 0.081, and 0.074 mol hydrogen/ mol glycerol, respectively. For continuous production of hydrogen, a semi-continuous process was performed. The medium containing glycerol 20 g/l at 5% loading rate of 1 liter working volume was daily feed for 14 days. The results revealed that hydrogen yield slightly increased and reached the maximum at day 6 with a value of 0.31 mol hydrogen/ mole glycerol. After, the hydrogen yield slightly decreased until day 8. At day 11, no hydrogen production was observed. During growth of E. coli HB41, acetic acid and ethanol were also produced. Acetic acid and ethanol production were 2.45 and 5.89 g/l, respectively. The increase in acetic acid resulted in decrease of pH from 7.0 at the beginning to 4.3 at the end of fermentation.