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Improved method for enumerating sulfate-reducing bacteria using optical density.

Bernardez LA, de Andrade Lima LR - MethodsX (2015)

Bottom Line: However, iron hydroxides also precipitate at high pH values and the presence of these precipitates interferes considerably in the optical density of the solution affecting estimates of the cell population thus seriously limiting the use of the conventional method.In this method a modification of the current method improves the measurement of the optical density of a solution with SRB cells. •The method consists of an acidification with hydrochloric acid of a sample of a mixed culture of SRB enriched from the produced water from oil fields to pH below 2.•The results show that the relationship between the bacterial dry mass and absorbance is exponential in the observed range.It was observed a large slope in the linearized fit equation, and the acidified solution does not change the integrity of the SRB cells after the treatment.•The results of the kinetic experiments, including the bacterial growth time evolution, demonstrate the applicability of the method.

View Article: PubMed Central - PubMed

Affiliation: Graduate Program of Industrial Engineering, Federal University of Bahia, Brazil.

ABSTRACT
The photometric determination of bacterial concentration can be affected by secondary scattering and other interferences. The conventional growth medium for sulfate-reducing bacteria (SRB) has iron that precipitates as iron sulfides, a dark precipitate which is useful to indicate bacterial activity. However, iron hydroxides also precipitate at high pH values and the presence of these precipitates interferes considerably in the optical density of the solution affecting estimates of the cell population thus seriously limiting the use of the conventional method. In this method a modification of the current method improves the measurement of the optical density of a solution with SRB cells. •The method consists of an acidification with hydrochloric acid of a sample of a mixed culture of SRB enriched from the produced water from oil fields to pH below 2.•The results show that the relationship between the bacterial dry mass and absorbance is exponential in the observed range. It was observed a large slope in the linearized fit equation, and the acidified solution does not change the integrity of the SRB cells after the treatment.•The results of the kinetic experiments, including the bacterial growth time evolution, demonstrate the applicability of the method.

No MeSH data available.


Batch kinetic tests for bioconversion of sulfate using SRB: (a) sulfate and sulfide solution content time evolution, (b) solution oxidation–reduction potential time evolution. (d) Biomass solution content time evolution.
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fig0015: Batch kinetic tests for bioconversion of sulfate using SRB: (a) sulfate and sulfide solution content time evolution, (b) solution oxidation–reduction potential time evolution. (d) Biomass solution content time evolution.

Mentions: The bioprocess kinetics were determined in a batch reactor with an initial sulfate concentration of 1790 mg/L. Fig. 3a shows the profiles of residual sulfate (filled triangle symbols) and produced sulfide (cross symbols) concentrations as a function of time. In 360 h (15 days) the sulfate content decreased from 1790 to 22.2 mg/L (a conversion of about 98.8%) and the sulfide concentration increased to 592.6 mg/L. Fig. 3b shows the redox potential measurement (filled diamond symbols), which was used to indicate the bacterial activity due to the reducer character of the SRB. During this period, a gradual decrease in the solution redox potential was observed. Fig. 3c shows the biomass solution content (filled circle symbols) estimated using the methods presented in this study. One remarks the enhancement of the microbial solution content, which is correlated with the redox potential reduction and the sulfide formation.


Improved method for enumerating sulfate-reducing bacteria using optical density.

Bernardez LA, de Andrade Lima LR - MethodsX (2015)

Batch kinetic tests for bioconversion of sulfate using SRB: (a) sulfate and sulfide solution content time evolution, (b) solution oxidation–reduction potential time evolution. (d) Biomass solution content time evolution.
© Copyright Policy - CC BY
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4487919&req=5

fig0015: Batch kinetic tests for bioconversion of sulfate using SRB: (a) sulfate and sulfide solution content time evolution, (b) solution oxidation–reduction potential time evolution. (d) Biomass solution content time evolution.
Mentions: The bioprocess kinetics were determined in a batch reactor with an initial sulfate concentration of 1790 mg/L. Fig. 3a shows the profiles of residual sulfate (filled triangle symbols) and produced sulfide (cross symbols) concentrations as a function of time. In 360 h (15 days) the sulfate content decreased from 1790 to 22.2 mg/L (a conversion of about 98.8%) and the sulfide concentration increased to 592.6 mg/L. Fig. 3b shows the redox potential measurement (filled diamond symbols), which was used to indicate the bacterial activity due to the reducer character of the SRB. During this period, a gradual decrease in the solution redox potential was observed. Fig. 3c shows the biomass solution content (filled circle symbols) estimated using the methods presented in this study. One remarks the enhancement of the microbial solution content, which is correlated with the redox potential reduction and the sulfide formation.

Bottom Line: However, iron hydroxides also precipitate at high pH values and the presence of these precipitates interferes considerably in the optical density of the solution affecting estimates of the cell population thus seriously limiting the use of the conventional method.In this method a modification of the current method improves the measurement of the optical density of a solution with SRB cells. •The method consists of an acidification with hydrochloric acid of a sample of a mixed culture of SRB enriched from the produced water from oil fields to pH below 2.•The results show that the relationship between the bacterial dry mass and absorbance is exponential in the observed range.It was observed a large slope in the linearized fit equation, and the acidified solution does not change the integrity of the SRB cells after the treatment.•The results of the kinetic experiments, including the bacterial growth time evolution, demonstrate the applicability of the method.

View Article: PubMed Central - PubMed

Affiliation: Graduate Program of Industrial Engineering, Federal University of Bahia, Brazil.

ABSTRACT
The photometric determination of bacterial concentration can be affected by secondary scattering and other interferences. The conventional growth medium for sulfate-reducing bacteria (SRB) has iron that precipitates as iron sulfides, a dark precipitate which is useful to indicate bacterial activity. However, iron hydroxides also precipitate at high pH values and the presence of these precipitates interferes considerably in the optical density of the solution affecting estimates of the cell population thus seriously limiting the use of the conventional method. In this method a modification of the current method improves the measurement of the optical density of a solution with SRB cells. •The method consists of an acidification with hydrochloric acid of a sample of a mixed culture of SRB enriched from the produced water from oil fields to pH below 2.•The results show that the relationship between the bacterial dry mass and absorbance is exponential in the observed range. It was observed a large slope in the linearized fit equation, and the acidified solution does not change the integrity of the SRB cells after the treatment.•The results of the kinetic experiments, including the bacterial growth time evolution, demonstrate the applicability of the method.

No MeSH data available.