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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.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.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).

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.


Main effects plot for (a) Biomass, (b) Acetic acid and (c) Ethanol.
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ijerph-12-01029-f002: Main effects plot for (a) Biomass, (b) Acetic acid and (c) Ethanol.

Mentions: The main effects plot for the experimental responses is shown in Figure 2. It represents the mean response values at each level of the design parameters. A main effect is considered present when the mean response changes across the level of the factor. From the main effects plot for biomass (Figure 2a), it is clearly observed that NH4Cl does not exert any significant effect on biomass. However, a slightly higher biomass concentration was observed whenever low NH4Cl concentrations were used in this study. This effect is in agreement with previously reported studies with Clostridium aceticum and Rhodospirillum rubrum using CO as the sole carbon substrate [16]. The presence of both NH4+ and acetate could presumably result in the formation of ammonium acetate which is inhibitory to some clostridia, already at low concentrations [17].


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)

Main effects plot for (a) Biomass, (b) Acetic acid and (c) Ethanol.
© Copyright Policy
Related In: Results  -  Collection

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

ijerph-12-01029-f002: Main effects plot for (a) Biomass, (b) Acetic acid and (c) Ethanol.
Mentions: The main effects plot for the experimental responses is shown in Figure 2. It represents the mean response values at each level of the design parameters. A main effect is considered present when the mean response changes across the level of the factor. From the main effects plot for biomass (Figure 2a), it is clearly observed that NH4Cl does not exert any significant effect on biomass. However, a slightly higher biomass concentration was observed whenever low NH4Cl concentrations were used in this study. This effect is in agreement with previously reported studies with Clostridium aceticum and Rhodospirillum rubrum using CO as the sole carbon substrate [16]. The presence of both NH4+ and acetate could presumably result in the formation of ammonium acetate which is inhibitory to some clostridia, already at low concentrations [17].

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.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.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).

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.