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A Novel Electrophototrophic Bacterium Rhodopseudomonas palustris Strain RP2, Exhibits Hydrocarbonoclastic Potential in Anaerobic Environments.

Venkidusamy K, Megharaj M - Front Microbiol (2016)

Bottom Line: Salient properties of the strain RP2 were direct electrode respiration, dissimilatory metal oxide reduction, spore formation, anaerobic nitrate reduction, free living diazotrophy and the ability to degrade n-alkane components of petroleum hydrocarbons (PH) in anoxic, photic environments.The ability of strain RP2 to produce current (maximum current density 21 ± 3 mA/m(2); power density 720 ± 7 μW/m(2), 1000 Ω) using PH as a sole energy source was also examined using an initial concentration of 800 mg l(-1) of diesel range hydrocarbons (C9-C36) with a concomitant removal of 47.4 ± 2.7% hydrocarbons in MERS.Such observations reveal the importance of photoorganotrophic growth in the utilization of hydrocarbons from contaminated environments.

View Article: PubMed Central - PubMed

Affiliation: Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes, SAAustralia; CRC for Contamination Assessment and Remediation of the Environment, Mawson Lakes, SAAustralia.

ABSTRACT
An electrophototrophic, hydrocarbonoclastic bacterium Rhodopseudomonas palustris stain RP2 was isolated from the anodic biofilms of hydrocarbon fed microbial electrochemical remediation systems (MERS). Salient properties of the strain RP2 were direct electrode respiration, dissimilatory metal oxide reduction, spore formation, anaerobic nitrate reduction, free living diazotrophy and the ability to degrade n-alkane components of petroleum hydrocarbons (PH) in anoxic, photic environments. In acetate fed microbial electrochemical cells, a maximum current density of 305 ± 10 mA/m(2) (1000Ω) was generated (power density 131.65 ± 10 mW/m(2)) by strain RP2 with a coulombic efficiency of 46.7 ± 1.3%. Cyclic voltammetry studies showed that anaerobically grown cells of strain RP2 is electrochemically active and likely to transfer electrons extracellularly to solid electron acceptors through membrane bound compounds, however, aerobically grown cells lacked the electrochemical activity. The ability of strain RP2 to produce current (maximum current density 21 ± 3 mA/m(2); power density 720 ± 7 μW/m(2), 1000 Ω) using PH as a sole energy source was also examined using an initial concentration of 800 mg l(-1) of diesel range hydrocarbons (C9-C36) with a concomitant removal of 47.4 ± 2.7% hydrocarbons in MERS. Here, we also report the first study that shows an initial evidence for the existence of a hydrocarbonoclastic behavior in the strain RP2 when grown in different electron accepting and illuminated conditions (anaerobic and MERS degradation). Such observations reveal the importance of photoorganotrophic growth in the utilization of hydrocarbons from contaminated environments. Identification of such novel petrochemical hydrocarbon degrading electricigens, not only expands the knowledge on the range of bacteria known for the hydrocarbon bioremediation but also shows a biotechnological potential that goes well beyond its applications to MERS.

No MeSH data available.


Related in: MedlinePlus

(A) A few representative initial cycles of current density (average from triplicates) generated by strain RP2 fed with acetate. (B) Power density and voltage generation as a function of current density from strain RP2 inoculated acetate-fed bottle MFCs. (C) Coulombic efficiency (CE) of a few representative batches of acetate-fed bottle MFCs.
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Figure 3: (A) A few representative initial cycles of current density (average from triplicates) generated by strain RP2 fed with acetate. (B) Power density and voltage generation as a function of current density from strain RP2 inoculated acetate-fed bottle MFCs. (C) Coulombic efficiency (CE) of a few representative batches of acetate-fed bottle MFCs.

Mentions: Current was generated in all the MFCs inoculated with strain RP2 using acetate as an energy source. After three days, voltage started to follow a constant pattern and then stabilized. The fuel cell electrodes were discharged through a 1000 Ω external resistance once it reached the plateau voltage generation stage. The voltage fell quickly from 690 ± 10 mV to 446 ± 5 mV after a 1000 Ω fixed resistor was connected. The maximum output range of voltage and current density were 446 ± 7 mV, 305 ± 10 mA/m2 (R = 1000 Ω) after four cycles of operation. Few representative initial cycles (average current density from triplicates) of current density are shown in (Figure 3A). After six refilling batches with a fresh substrate, the maximum current output of each batch became stable (300 ± 7 mA/m2). The maximum open circuit voltage was 700 ± 7 mV and attainable power density was 131.65 ± 10 mW/m2 (R = 1000 Ω) (Figure 3B). The CEs showed the increased trend with the increased current densities as shown in the Figure 3C. The maximum CE was 46.7% which corresponded to the maximum current density of 259.90 mA/m2. The higher buffer (200 mM) concentration were also examined at the same resistance which produced a maximum power density of 300 ± 20 mW/m2.


A Novel Electrophototrophic Bacterium Rhodopseudomonas palustris Strain RP2, Exhibits Hydrocarbonoclastic Potential in Anaerobic Environments.

Venkidusamy K, Megharaj M - Front Microbiol (2016)

(A) A few representative initial cycles of current density (average from triplicates) generated by strain RP2 fed with acetate. (B) Power density and voltage generation as a function of current density from strain RP2 inoculated acetate-fed bottle MFCs. (C) Coulombic efficiency (CE) of a few representative batches of acetate-fed bottle MFCs.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4940424&req=5

Figure 3: (A) A few representative initial cycles of current density (average from triplicates) generated by strain RP2 fed with acetate. (B) Power density and voltage generation as a function of current density from strain RP2 inoculated acetate-fed bottle MFCs. (C) Coulombic efficiency (CE) of a few representative batches of acetate-fed bottle MFCs.
Mentions: Current was generated in all the MFCs inoculated with strain RP2 using acetate as an energy source. After three days, voltage started to follow a constant pattern and then stabilized. The fuel cell electrodes were discharged through a 1000 Ω external resistance once it reached the plateau voltage generation stage. The voltage fell quickly from 690 ± 10 mV to 446 ± 5 mV after a 1000 Ω fixed resistor was connected. The maximum output range of voltage and current density were 446 ± 7 mV, 305 ± 10 mA/m2 (R = 1000 Ω) after four cycles of operation. Few representative initial cycles (average current density from triplicates) of current density are shown in (Figure 3A). After six refilling batches with a fresh substrate, the maximum current output of each batch became stable (300 ± 7 mA/m2). The maximum open circuit voltage was 700 ± 7 mV and attainable power density was 131.65 ± 10 mW/m2 (R = 1000 Ω) (Figure 3B). The CEs showed the increased trend with the increased current densities as shown in the Figure 3C. The maximum CE was 46.7% which corresponded to the maximum current density of 259.90 mA/m2. The higher buffer (200 mM) concentration were also examined at the same resistance which produced a maximum power density of 300 ± 20 mW/m2.

Bottom Line: Salient properties of the strain RP2 were direct electrode respiration, dissimilatory metal oxide reduction, spore formation, anaerobic nitrate reduction, free living diazotrophy and the ability to degrade n-alkane components of petroleum hydrocarbons (PH) in anoxic, photic environments.The ability of strain RP2 to produce current (maximum current density 21 ± 3 mA/m(2); power density 720 ± 7 μW/m(2), 1000 Ω) using PH as a sole energy source was also examined using an initial concentration of 800 mg l(-1) of diesel range hydrocarbons (C9-C36) with a concomitant removal of 47.4 ± 2.7% hydrocarbons in MERS.Such observations reveal the importance of photoorganotrophic growth in the utilization of hydrocarbons from contaminated environments.

View Article: PubMed Central - PubMed

Affiliation: Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes, SAAustralia; CRC for Contamination Assessment and Remediation of the Environment, Mawson Lakes, SAAustralia.

ABSTRACT
An electrophototrophic, hydrocarbonoclastic bacterium Rhodopseudomonas palustris stain RP2 was isolated from the anodic biofilms of hydrocarbon fed microbial electrochemical remediation systems (MERS). Salient properties of the strain RP2 were direct electrode respiration, dissimilatory metal oxide reduction, spore formation, anaerobic nitrate reduction, free living diazotrophy and the ability to degrade n-alkane components of petroleum hydrocarbons (PH) in anoxic, photic environments. In acetate fed microbial electrochemical cells, a maximum current density of 305 ± 10 mA/m(2) (1000Ω) was generated (power density 131.65 ± 10 mW/m(2)) by strain RP2 with a coulombic efficiency of 46.7 ± 1.3%. Cyclic voltammetry studies showed that anaerobically grown cells of strain RP2 is electrochemically active and likely to transfer electrons extracellularly to solid electron acceptors through membrane bound compounds, however, aerobically grown cells lacked the electrochemical activity. The ability of strain RP2 to produce current (maximum current density 21 ± 3 mA/m(2); power density 720 ± 7 μW/m(2), 1000 Ω) using PH as a sole energy source was also examined using an initial concentration of 800 mg l(-1) of diesel range hydrocarbons (C9-C36) with a concomitant removal of 47.4 ± 2.7% hydrocarbons in MERS. Here, we also report the first study that shows an initial evidence for the existence of a hydrocarbonoclastic behavior in the strain RP2 when grown in different electron accepting and illuminated conditions (anaerobic and MERS degradation). Such observations reveal the importance of photoorganotrophic growth in the utilization of hydrocarbons from contaminated environments. Identification of such novel petrochemical hydrocarbon degrading electricigens, not only expands the knowledge on the range of bacteria known for the hydrocarbon bioremediation but also shows a biotechnological potential that goes well beyond its applications to MERS.

No MeSH data available.


Related in: MedlinePlus