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Rescuing ethanol photosynthetic production of cyanobacteria in non-sterilized outdoor cultivations with a bicarbonate-based pH-rising strategy

View Article: PubMed Central - PubMed

ABSTRACT

Background: Ethanol photosynthetic production based on cyanobacteria cell factories utilizing CO2 and solar energy provides an attractive solution for sustainable production of green fuels. However, the scaling up processes of cyanobacteria cell factories were usually threatened or even devastated by biocontaminations, which restricted biomass or products accumulations of cyanobacteria cells. Thus it is of great significance to develop reliable biocontamination-controlling strategies for promoting ethanol photosynthetic production in large scales.

Results: The scaling up process of a previously developed Synechocystis strain Syn-HZ24 for ethanol synthesis was severely inhibited and devastated by a specific contaminant, Pannonibacter phragmitetus, which overcame the growths of cyanobacteria cells and completely consumed the ethanol accumulation in the cultivation systems. Physiological analysis revealed that growths and ethanol-consuming activities of the contaminant were sensitive to alkaline conditions, while ethanol-synthesizing cyanobacteria strain Syn-HZ24 could tolerate alkaline pH conditions as high as 11.0, indicating that pH-increasing strategy might be a feasible approach for rescuing ethanol photosynthetic production in outdoor cultivation systems. Thus, we designed and evaluated a Bicarbonate-based Integrated Carbon Capture System (BICCS) derived pH-rising strategy to rescue the ethanol photosynthetic production in non-sterilized conditions. In lab scale artificially simulated systems, pH values of BG11 culture medium were maintained around 11.0 by 180 mM NaHCO3 and air steam, under which the infection of Pannonibacter phragmitetus was significantly restricted, recovering ethanol production of Syn-HZ24 by about 80%. As for outdoor cultivations, ethanol photosynthetic production of Syn-HZ24 was also successfully rescued by the BICCS-derived pH-rising strategy, obtaining a final ethanol concentration of 0.9 g/L after 10 days cultivation.

Conclusions: In this work, a novel product-consuming biocontamination pattern in cyanobacteria cultivations, causing devastated ethanol photosynthetic production, was identified and characterized. Physiological analysis of the essential ethanol-consuming contaminant directed the design and application of a pH-rising strategy, which effectively and selectively controlled the contamination and rescued ethanol photosynthetic production. Our work demonstrated the importance of reliable contamination control systems and strategies for large scale outdoor cultivations of cyanobacteria, and provided an inspiring paradigm for targeting effective solutions.

Electronic supplementary material: The online version of this article (doi:10.1186/s13068-017-0765-5) contains supplementary material, which is available to authorized users.

No MeSH data available.


Effects of sodium chloride and high pH stress on growth and ethanol-consuming activities of Pannonibacter phragmitetus. a Growth (left) and ethanol consumption (right) of Pannonibacter phragmitetus in BG11 medium with 0 mM NaCl (shown in black column), 300 mM NaCl (shown in red column) and 600 mM NaCl (shown in blue column). b Growths of Pannonibacter phragmitetus in BG11 medium with original pH (open circle) and pH 10 (open triangle). c Ethanol consuming activities of Pannonibacter phragmitetus in BG11 medium with original pH (open circle) and pH 10 (open triangle), the natural evaporation (open square) was taken as a control. Error bars corresponded to the standard deviation determined from three independent experiments. d Growths of Pannonibacter phragmitetus cells cultivated in BG11 medium with original pH, pH 10 and pH 11.0 for 3 days
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Fig3: Effects of sodium chloride and high pH stress on growth and ethanol-consuming activities of Pannonibacter phragmitetus. a Growth (left) and ethanol consumption (right) of Pannonibacter phragmitetus in BG11 medium with 0 mM NaCl (shown in black column), 300 mM NaCl (shown in red column) and 600 mM NaCl (shown in blue column). b Growths of Pannonibacter phragmitetus in BG11 medium with original pH (open circle) and pH 10 (open triangle). c Ethanol consuming activities of Pannonibacter phragmitetus in BG11 medium with original pH (open circle) and pH 10 (open triangle), the natural evaporation (open square) was taken as a control. Error bars corresponded to the standard deviation determined from three independent experiments. d Growths of Pannonibacter phragmitetus cells cultivated in BG11 medium with original pH, pH 10 and pH 11.0 for 3 days

Mentions: As shown in Fig. 3a, when NaCl concentrations in BG11 culture medium reached 600 mM, neither growths nor ethanol-consuming activities of Pannonibacter phragmitetus were inhibited, indicating hypersaline conditions might not be an acceptable strategy for controlling infection of Pannonibacter phragmitetus. In addition, Pannonibacter phragmitetus could grow in BG11 culture medium supplemented with ethanol independently with cyanobacteria indicated that ethanol could be absorbed and converted by this contaminant as sole carbon sources.Fig. 3


Rescuing ethanol photosynthetic production of cyanobacteria in non-sterilized outdoor cultivations with a bicarbonate-based pH-rising strategy
Effects of sodium chloride and high pH stress on growth and ethanol-consuming activities of Pannonibacter phragmitetus. a Growth (left) and ethanol consumption (right) of Pannonibacter phragmitetus in BG11 medium with 0 mM NaCl (shown in black column), 300 mM NaCl (shown in red column) and 600 mM NaCl (shown in blue column). b Growths of Pannonibacter phragmitetus in BG11 medium with original pH (open circle) and pH 10 (open triangle). c Ethanol consuming activities of Pannonibacter phragmitetus in BG11 medium with original pH (open circle) and pH 10 (open triangle), the natural evaporation (open square) was taken as a control. Error bars corresponded to the standard deviation determined from three independent experiments. d Growths of Pannonibacter phragmitetus cells cultivated in BG11 medium with original pH, pH 10 and pH 11.0 for 3 days
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5391583&req=5

Fig3: Effects of sodium chloride and high pH stress on growth and ethanol-consuming activities of Pannonibacter phragmitetus. a Growth (left) and ethanol consumption (right) of Pannonibacter phragmitetus in BG11 medium with 0 mM NaCl (shown in black column), 300 mM NaCl (shown in red column) and 600 mM NaCl (shown in blue column). b Growths of Pannonibacter phragmitetus in BG11 medium with original pH (open circle) and pH 10 (open triangle). c Ethanol consuming activities of Pannonibacter phragmitetus in BG11 medium with original pH (open circle) and pH 10 (open triangle), the natural evaporation (open square) was taken as a control. Error bars corresponded to the standard deviation determined from three independent experiments. d Growths of Pannonibacter phragmitetus cells cultivated in BG11 medium with original pH, pH 10 and pH 11.0 for 3 days
Mentions: As shown in Fig. 3a, when NaCl concentrations in BG11 culture medium reached 600 mM, neither growths nor ethanol-consuming activities of Pannonibacter phragmitetus were inhibited, indicating hypersaline conditions might not be an acceptable strategy for controlling infection of Pannonibacter phragmitetus. In addition, Pannonibacter phragmitetus could grow in BG11 culture medium supplemented with ethanol independently with cyanobacteria indicated that ethanol could be absorbed and converted by this contaminant as sole carbon sources.Fig. 3

View Article: PubMed Central - PubMed

ABSTRACT

Background: Ethanol photosynthetic production based on cyanobacteria cell factories utilizing CO2 and solar energy provides an attractive solution for sustainable production of green fuels. However, the scaling up processes of cyanobacteria cell factories were usually threatened or even devastated by biocontaminations, which restricted biomass or products accumulations of cyanobacteria cells. Thus it is of great significance to develop reliable biocontamination-controlling strategies for promoting ethanol photosynthetic production in large scales.

Results: The scaling up process of a previously developed Synechocystis strain Syn-HZ24 for ethanol synthesis was severely inhibited and devastated by a specific contaminant, Pannonibacter phragmitetus, which overcame the growths of cyanobacteria cells and completely consumed the ethanol accumulation in the cultivation systems. Physiological analysis revealed that growths and ethanol-consuming activities of the contaminant were sensitive to alkaline conditions, while ethanol-synthesizing cyanobacteria strain Syn-HZ24 could tolerate alkaline pH conditions as high as 11.0, indicating that pH-increasing strategy might be a feasible approach for rescuing ethanol photosynthetic production in outdoor cultivation systems. Thus, we designed and evaluated a Bicarbonate-based Integrated Carbon Capture System (BICCS) derived pH-rising strategy to rescue the ethanol photosynthetic production in non-sterilized conditions. In lab scale artificially simulated systems, pH values of BG11 culture medium were maintained around 11.0 by 180 mM NaHCO3 and air steam, under which the infection of Pannonibacter phragmitetus was significantly restricted, recovering ethanol production of Syn-HZ24 by about 80%. As for outdoor cultivations, ethanol photosynthetic production of Syn-HZ24 was also successfully rescued by the BICCS-derived pH-rising strategy, obtaining a final ethanol concentration of 0.9 g/L after 10 days cultivation.

Conclusions: In this work, a novel product-consuming biocontamination pattern in cyanobacteria cultivations, causing devastated ethanol photosynthetic production, was identified and characterized. Physiological analysis of the essential ethanol-consuming contaminant directed the design and application of a pH-rising strategy, which effectively and selectively controlled the contamination and rescued ethanol photosynthetic production. Our work demonstrated the importance of reliable contamination control systems and strategies for large scale outdoor cultivations of cyanobacteria, and provided an inspiring paradigm for targeting effective solutions.

Electronic supplementary material: The online version of this article (doi:10.1186/s13068-017-0765-5) contains supplementary material, which is available to authorized users.

No MeSH data available.