Sulfide assessment in bioreactors with gas replacement

Hu, Peng; Jacobsen, Lee T.; Horton, James G.; Lewis, Randy S.

doi:10.1016/j.bej.2010.02.006

Cited by 21 publications

(7 citation statements)

References 17 publications

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“…Similar multiple growth phases have been reported previously with P11 and C. acetobutylicum fermentations (Ramachandriya et al, 2010; Tracy et al, 2008). Maximum cell mass concentrations for P11 and P7 were almost twice that observed in previous studies using bottle reactors (Ahmed et al, 2006; Hu et al, 2010; Ramachandriya et al, 2010). This could be due to the fact that the headspace gas to culture volume ratio was 2.5 times greater in the current study compared to previous studies (Ramachandriya et al, 2010).…”

Section: Resultssupporting

confidence: 43%

Reduction of acetone to isopropanol using producer gas fermenting microbes

Ramachandriya

Wilkins

Delorme

et al. 2011

Biotech & Bioengineering

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Gasification-fermentation is an emerging technology for the conversion of lignocellulosic materials into biofuels and specialty chemicals. For effective utilization of producer gas by fermenting bacteria, tar compounds produced in the gasification process are often removed by wet scrubbing techniques using acetone. In a preliminary study using biomass generated producer gas scrubbed with acetone, an accumulation of acetone and subsequent isopropanol production was observed. The effect of 2 g/L acetone concentrations in the fermentation media on growth and product distributions was studied with "Clostridium ragsdalei," also known as Clostridium strain P11 or P11, and Clostridium carboxidivorans P7 or P7. The reduction of acetone to isopropanol was possible with "C. ragsdalei," but not with P7. In P11 this reaction occurred rapidly when acetone was added in the acidogenic phase, but was 2.5 times slower when added in the solventogenic phase. Acetone at concentrations of 2 g/L did not affect the growth of P7, but ethanol increased by 41% and acetic acid concentrations decreased by 79%. In the fermentations using P11, growth was unaffected and ethanol concentrations increased by 55% when acetone was added in the acidogenic phase. Acetic acid concentrations increased by 19% in both the treatments where acetone was added. Our observations indicate that P11 has a secondary alcohol dehydrogenase that enables it to reduce acetone to isopropanol, while P7 lacks this enzyme. P11 offers an opportunity for biological production of isopropanol from acetone reduction in the presence of gaseous substrates (CO, CO₂, and H₂).

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Section: Resultssupporting

confidence: 43%

Reduction of acetone to isopropanol using producer gas fermenting microbes

Ramachandriya

Wilkins

Delorme

et al. 2011

Biotech & Bioengineering

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“…Frankman found that the reducing agent cysteine sulfide had a bigger influence on redox potential than the composition of the syngas used in the fermentation vessel during growth of Clostridium carboxidivorans for ethanol production [49]. In fact, Hu et al found that higher cysteine sulfide concentrations in the media during growth of Clostridium strain P11 on synthetic-mixed (SM) syngas led to enhanced ethanol production, while lower concentrations triggered acetogenesis [48]. Another approach used to raise the overall ethanol yield obtained from syngas fermentation is conversion of the acetate fraction from the product broth to H 2 and CO 2 with microbial oxidation.…”

Section: Synthesis Gas Fermentationmentioning

confidence: 98%

“…Efforts to increase the ethanol yield over acetate in Clostridia include supplementing the media, nutrient limiting conditions (e.g., nitrogen limitation), addition of a reducing agent, pH shifts and addition of H 2 [15, 43,[45][46][47][48]. The availability of reducing agents is important because they lower the reduction-oxidation (redox) levels of the microbial environment and impact the solubility of nutrients.…”

Section: Synthesis Gas Fermentationmentioning

confidence: 99%

Gasification and synthesis gas fermentation: an alternative route to biofuel production

Slivka

Chinn

Grunden³

2011

Biofuels

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“…The sulfur containing gases (e.g. H 2 S) present in syngas are toxic to chemical catalysts but can be beneficial for microbial catalysts by reducing medium redox potential, stimulate redox sensitive enzymes such as CODH, and promote alcohol formation [206,207].…”

Section: Medium Formulationmentioning

confidence: 99%