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Ethanol and acetic acid production from carbon monoxide in a clostridium strain in batch and continuous gas-fed bioreactors.

Abubackar HN, Veiga MC, Kennes C - Int J Environ Res Public Health (2015)

Bottom Line: The effect of different sources of nitrogen as well as their concentrations on the bioconversion of carbon monoxide to metabolic products such as acetic acid and ethanol by Clostridium autoethanogenum was studied.When compared to EXP2 and EXP3, it was found that EXP1 yielded the maximum biomass accumulation (302.4 mg/L) and products concentrations, i.e., acetic acid (2147.1 mg/L) and ethanol (352.6 mg/L).However, when ethanol is the desired end-product, as a biofuel, the lower pH used in EXP2 was more favourable for solventogenesis and yielded the highest ethanol/acetic acid ratio, reaching a value of 0.54.

View Article: PubMed Central - PubMed

Affiliation: Chemical Engineering Laboratory, Faculty of Sciences, University of La Coruña, Rúa da Fraga 10, 15008 La Coruña, Spain. harisnalakath@yahoo.com.

ABSTRACT
The effect of different sources of nitrogen as well as their concentrations on the bioconversion of carbon monoxide to metabolic products such as acetic acid and ethanol by Clostridium autoethanogenum was studied. In a first set of assays, under batch conditions, either NH4Cl, trypticase soy broth or yeast extract (YE) were used as sources of nitrogen. The use of YE was found statistically significant (p < 0.05) on the product spectrum in such batch assays. In another set of experiments, three bioreactors were operated with continuous CO supply, in order to estimate the effect of running conditions on products and biomass formation. The bioreactors were operated under different conditions, i.e., EXP1 (pH = 5.75, YE 1g/L), EXP2 (pH = 4.75, YE 1 g/L) and EXP3 (pH = 5.75, YE 0.2 g/L). When compared to EXP2 and EXP3, it was found that EXP1 yielded the maximum biomass accumulation (302.4 mg/L) and products concentrations, i.e., acetic acid (2147.1 mg/L) and ethanol (352.6 mg/L). This can be attributed to the fact that the higher pH and higher YE concentration used in EXP1 stimulated cell growth and did, consequently, also enhance metabolite production. However, when ethanol is the desired end-product, as a biofuel, the lower pH used in EXP2 was more favourable for solventogenesis and yielded the highest ethanol/acetic acid ratio, reaching a value of 0.54.

No MeSH data available.


Related in: MedlinePlus

Cell mass (a) and products profiles, Acetic acid (b); Ethanol (c) and Butanediol (d) in three different experiments: EXP1 (pH = 5.75 and YE 1 g/L); EXP2 (pH = 4.75 and YE 1 g/L); EXP3 (pH = 5.75 and YE 0.2 g/L).
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ijerph-12-01029-f004: Cell mass (a) and products profiles, Acetic acid (b); Ethanol (c) and Butanediol (d) in three different experiments: EXP1 (pH = 5.75 and YE 1 g/L); EXP2 (pH = 4.75 and YE 1 g/L); EXP3 (pH = 5.75 and YE 0.2 g/L).

Mentions: Bioreactor experiments with continuous gas-flow, i.e., continuous CO supply, were performed for up to two weeks each. Cell growth and the production of different metabolites in three different sets of experiments are shown in Figure 4. The redox potential was constantly monitored for each experimental run. It is related to the electron transfer undergoing inside the cells and hence is very sensitive for even delicate changes in metabolism. Both EXP1 and EXP3 had an instrument reading oxidoreduction potential (ORP) value of −87 ± 10 mV, while it was −43 ± 5 mV for EXP2. The ORP values are directly dependant on the pH of the medium. A lower pH of the liquid phase will result in lower negative values of the redox potential. Oscillations of the redox potential values in the culture medium could be due to microbial growth and variations in the metabolic profile at each point of the experimental run and have also been reported by other researchers in other bioconversion studies [20,21]. Intracellular redox homeostasis is profoundly affected by the ups and downs of the extracellular redox potential which can significantly switch the fermentation type in acidogenic bacteria [22].


Ethanol and acetic acid production from carbon monoxide in a clostridium strain in batch and continuous gas-fed bioreactors.

Abubackar HN, Veiga MC, Kennes C - Int J Environ Res Public Health (2015)

Cell mass (a) and products profiles, Acetic acid (b); Ethanol (c) and Butanediol (d) in three different experiments: EXP1 (pH = 5.75 and YE 1 g/L); EXP2 (pH = 4.75 and YE 1 g/L); EXP3 (pH = 5.75 and YE 0.2 g/L).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4306909&req=5

ijerph-12-01029-f004: Cell mass (a) and products profiles, Acetic acid (b); Ethanol (c) and Butanediol (d) in three different experiments: EXP1 (pH = 5.75 and YE 1 g/L); EXP2 (pH = 4.75 and YE 1 g/L); EXP3 (pH = 5.75 and YE 0.2 g/L).
Mentions: Bioreactor experiments with continuous gas-flow, i.e., continuous CO supply, were performed for up to two weeks each. Cell growth and the production of different metabolites in three different sets of experiments are shown in Figure 4. The redox potential was constantly monitored for each experimental run. It is related to the electron transfer undergoing inside the cells and hence is very sensitive for even delicate changes in metabolism. Both EXP1 and EXP3 had an instrument reading oxidoreduction potential (ORP) value of −87 ± 10 mV, while it was −43 ± 5 mV for EXP2. The ORP values are directly dependant on the pH of the medium. A lower pH of the liquid phase will result in lower negative values of the redox potential. Oscillations of the redox potential values in the culture medium could be due to microbial growth and variations in the metabolic profile at each point of the experimental run and have also been reported by other researchers in other bioconversion studies [20,21]. Intracellular redox homeostasis is profoundly affected by the ups and downs of the extracellular redox potential which can significantly switch the fermentation type in acidogenic bacteria [22].

Bottom Line: The effect of different sources of nitrogen as well as their concentrations on the bioconversion of carbon monoxide to metabolic products such as acetic acid and ethanol by Clostridium autoethanogenum was studied.When compared to EXP2 and EXP3, it was found that EXP1 yielded the maximum biomass accumulation (302.4 mg/L) and products concentrations, i.e., acetic acid (2147.1 mg/L) and ethanol (352.6 mg/L).However, when ethanol is the desired end-product, as a biofuel, the lower pH used in EXP2 was more favourable for solventogenesis and yielded the highest ethanol/acetic acid ratio, reaching a value of 0.54.

View Article: PubMed Central - PubMed

Affiliation: Chemical Engineering Laboratory, Faculty of Sciences, University of La Coruña, Rúa da Fraga 10, 15008 La Coruña, Spain. harisnalakath@yahoo.com.

ABSTRACT
The effect of different sources of nitrogen as well as their concentrations on the bioconversion of carbon monoxide to metabolic products such as acetic acid and ethanol by Clostridium autoethanogenum was studied. In a first set of assays, under batch conditions, either NH4Cl, trypticase soy broth or yeast extract (YE) were used as sources of nitrogen. The use of YE was found statistically significant (p < 0.05) on the product spectrum in such batch assays. In another set of experiments, three bioreactors were operated with continuous CO supply, in order to estimate the effect of running conditions on products and biomass formation. The bioreactors were operated under different conditions, i.e., EXP1 (pH = 5.75, YE 1g/L), EXP2 (pH = 4.75, YE 1 g/L) and EXP3 (pH = 5.75, YE 0.2 g/L). When compared to EXP2 and EXP3, it was found that EXP1 yielded the maximum biomass accumulation (302.4 mg/L) and products concentrations, i.e., acetic acid (2147.1 mg/L) and ethanol (352.6 mg/L). This can be attributed to the fact that the higher pH and higher YE concentration used in EXP1 stimulated cell growth and did, consequently, also enhance metabolite production. However, when ethanol is the desired end-product, as a biofuel, the lower pH used in EXP2 was more favourable for solventogenesis and yielded the highest ethanol/acetic acid ratio, reaching a value of 0.54.

No MeSH data available.


Related in: MedlinePlus