Hydrogen production by Thermotoga lettingae using spent fermentation media containing acetic acid.

摘要

Biological production of hydrogen (H2) gas from fermentation of agricultural feedstock is one method to produce clean and sustainable source of energy. During fermentation of glucose to H2, acetic acid and carbon dioxide (CO2) by Thermotoga neapolitana, only 33% of the energy contained in glucose is converted to hydrogen. The aim of this study was to use a second thermotogale, Thermotoga lettingae to ferment sugars and acetic acid in spent media to produce H 2. Hydrogen production by this bacterium in fresh and spent media was studied by quantifying the amount of substrate consumed and products formed. The effect of H2 inhibition on H2 production was investigated by conducting fermentations with various volumes of media.;H2 gas was produced by Thermotoga lettingae in glucose medium, acetic acid medium and spent fermentation media. H2 inhibition caused a significant reduction in H2 concentration for fresh and spent media. Hydrogen yield for bottles with lowest volume containing glucose and acetic acid media was 0.031 g H2/g COD used and 0.052 g H2/g COD used respectively. Batch incubation of Thermotoga lettingae in unfiltered spent medium containing glucose produced 29mmol of H2/ L of medium at lowest volume while the filtered medium inoculated with the bacterium 8.51 mmol of H2/ L of medium. Similar trend was seen for the spent fermentation media containing no residual glucose. While unfiltered medium inoculated with the bacterium produced be 16.96 mmol of H2/ L of medium, 12.51 mmol of H2/ L of medium were produced in filtered medium. The yield values for unfiltered and filtered media without residual glucose was 0.106 g H2/g COD and 0.080 g H2/g COD respectively for bottles with lowest volume of media. This process is in accordance with the concept of a biorefinery to utilize all byproducts. Production of H2 from spent acetic acid media is an important result which has not been documented by previous studies.