Linear growth and poly( -hydroxybutyrate) synthesis in response to pulse-wise addition of the growth-limiting substrate to steady-state heterotrophic continuous cultures of Aquaspirillum autotrophicum

Pagni, Marco; Beffa, Trello; Isch, Cédric; Aragno, Michel

doi:10.1099/00221287-138-3-429

Cited by 19 publications

(7 citation statements)

References 27 publications

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“…) (Beun et al, 2000a;Pagni et al, 1992;Van Aalst-Van Leeuwen et al, 1997;Van Niel et al, 1995). Beun et al (2000a) showed that, at SRTs of 9.5 and 19.8 days, the ratio of PHB produced over acetate consumed (r PHB /r Ac ) was 0.60 Cmol PHB/Cmol, similar to the values observed in this study at low oxygen supply rates (Table I).…”

Section: Relationship Between Phb Synthesis and Specific Growth Ratesupporting

confidence: 91%

The effect of dissolved oxygen on PHB accumulation in activated sludge cultures

Third

Newland²,

Cord‐Ruwisch

2003

Biotech & Bioengineering

116

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Nitrogen removal from wastewater is often limited by the availability of reducing power to perform denitrification, especially when treating wastewaters with a low carbon:nitrogen ratio. In the increasingly popular sequencing batch reactor (SBR), bacteria have the opportunity to preserve reducing power from incoming chemical oxygen demand (COD) as poly-beta-hydroxybutyrate (PHB). The current study uses laboratory experiments and mathematical modeling in an attempt to generate a better understanding of the effect of oxygen on microbial conversion of COD into PHB. Results from a laboratory SBR with acetate as the organic carbon source showed that the aerobic acetate uptake process was oxygen-dependent, producing higher uptake rates at higher dissolved oxygen (DO) supply rates. However, at the lower DO supply rates (k(L)a 6 to 16 h(-1), 0 mg L(-1) DO), a higher proportion of the substrate was preserved as PHB than at higher DO supply rates (k(L)a 30, 51 h(-1), DO >0.9 mg L(-1)). Up to 77% of the reducing equivalents available from acetate were converted to PHB under oxygen limitation (Y(PHB/Ac) 0.68 Cmol/Cmol), as opposed to only 54% under oxygen-excess conditions (Y(PHB/Ac) 0.48 Cmol/Cmol), where a higher fraction of acetate was used for biomass growth. It was calculated that, by oxygen management during the feast phase, the amount of PHB preserved (1.4 Cmmol L(-1) PHB) accounted for an additional denitrification potential of up to 18 mg L(-1) nitrate-nitrogen. The trends of the effect of oxygen (and hence ATP availability) on PHB accumulation could be reproduced by the simulation model, which was based on biochemical stoichiometry and maximum rates obtained from experiments. Simulated data showed that, at low DO concentrations, the limited availability of adenosine triphosphate (ATP) prevented significant biomass growth and most ATP was used for acetate transport into the cell. In contrast, high DO supply rates provided surplus ATP and hence higher growth rates, resulting in decreased PHB yields. The results suggest that oxygen management is crucial to conserving reducing power during the feast phase of SBR operation, as excessive aeration rates decrease the PHB yield and allow higher biomass growth.

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Section: Relationship Between Phb Synthesis and Specific Growth Ratesupporting

confidence: 91%

The effect of dissolved oxygen on PHB accumulation in activated sludge cultures

Third

Newland²,

Cord‐Ruwisch

2003

Biotech & Bioengineering

116

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“…This result is in agreement with the results of other studies that found no relationship between the steady-state growth rates of cultures and the acetate uptake rates after pulse-wise addition of substrate (21,29). It is also likely that the acetate uptake pathway was fully induced in the chemostat-grown PHB(Ϫ) culture despite the lower measured acetate uptake rate.…”

Section: Resultssupporting

confidence: 83%

rRNA and Poly-β-Hydroxybutyrate Dynamics in Bioreactors Subjected to Feast and Famine Cycles

Frigon

Muyzer

Loosdrecht

et al. 2006

Appl Environ Microbiol

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Feast and famine cycles are common in activated sludge wastewater treatment systems, and they select for bacteria that accumulate storage compounds, such as poly-␤-hydroxybutyrate (PHB). Previous studies have shown that variations in influent substrate concentrations force bacteria to accumulate high levels of rRNA compared to the levels in bacteria grown in chemostats. Therefore, it can be hypothesized that bacteria accumulate more rRNA when they are subjected to feast and famine cycles. However, PHB-accumulating bacteria can form biomass (grow) throughout a feast and famine cycle and thus have a lower peak biomass formation rate during the cycle. Consequently, PHB-accumulating bacteria may accumulate less rRNA when they are subjected to feast and famine cycles than bacteria that are not capable of PHB accumulation. These hypotheses were tested with Wautersia eutropha H16 (wild type) and W. eutropha PHB-4 (a mutant not capable of accumulating PHB) grown in chemostat and semibatch reactors. For both strains, the cellular RNA level was higher when the organism was grown in semibatch reactors than when it was grown in chemostats, and the specific biomass formation rates during the feast phase were linearly related to the cellular RNA levels for cultures. Although the two strains exhibited maximum uptake rates when they were grown in semibatch reactors, the wild-type strain responded much more rapidly to the addition of fresh medium than the mutant responded. Furthermore, the chemostat-grown mutant culture was unable to exhibit maximum substrate uptake rates when it was subjected to pulse-wise addition of fresh medium. These data show that the ability to accumulate PHB does not prevent bacteria from accumulating high levels of rRNA when they are subjected to feast and famine cycles. Our results also demonstrate that the ability to accumulate PHB makes the bacteria more responsive to sudden increases in substrate concentrations, which explains their ecological advantage.rRNA-targeted hybridization techniques, such as fluorescence in situ hybridization and oligonucleotide membrane hybridization, are increasingly used to study microbial population diversity and dynamics in wastewater treatment systems (34). Although the temporal trends determined by these two techniques often agree with each other, their evaluations of population abundance may differ considerably. For example, Oerther and coworkers (19) reported that the Acinetobacter spp. population accounted for up to 43% of the total rRNA, while this population accounted for only up to 4.4% of the total number of cells in a municipal activated sludge system, suggesting that the cellular rRNA levels for this population were relatively high. In a related study, an opposite trend was found for the Gordonia spp. population in the same activated sludge treatment system (20). Some of the discrepancies can probably be explained by variation in the regulation of rRNA between species. However, the reactor conditions, specific metabolic functions, and ecological interactions...

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“…However, the fate of the substrate under these conditions has rarely been studied. Pagni et al (1992) and van Niel et al (1995) studied this phenomenon and also found a correlation between lower growth rate before addition of the substrate pulse and higher PHB accumulation after the substrate pulse. The exact mechanism behind these observations was not described.…”

Section: Discussionmentioning

confidence: 88%

“…For this purpose an acetic-acid-limited continuous culture of Paracoccus pantotrophus was used. This culture was turned to the batch mode and a pulse of acetate was added (Pagni et al, 1992;van Niel, 1995). Both the production of PHB when acetate is present in excess and the consumption of PHB when acetate is depleted were followed.…”

Section: Introductionmentioning

confidence: 99%

Kinetic modeling of poly(β-hydroxybutyrate) production and consumption byParacoccus pantotrophus under dynamic substrate supply

Leeuwen

Pot

Loosdrecht

et al. 1997

Biotechnol. Bioeng.

132

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The objective of the research was to obtain insights into the behavior of microorganisms under feast/famine conditions as often occur in wastewater treatment processes. The response of microorganisms to such conditions is the accumulation of storage polymers like poly(β‐hydroxybutyrate). The research was performed using a pure culture of Paracoccus pantotrophus LMD 94.21. A steady‐state C‐limited chemostat culture was switched to batch mode and a pulse of acetate was added. As long as external substrate (acetic acid) was present, the organism grew and accumulated poly(β‐hydroxybutyrate). After depletion of the external substrate, the stored poly(β‐hydroxybutyrate) was used as growth substrate. Poly(β‐hydroxybutyrate) accumulation was found to be strongly dependent on the growth rate of the organism before the pulse addition of acetate. Poly(β‐hydroxybutyrate) accumulation was correlated to the difference in maximum acetate uptake rate and the acetate required for growth. Based on the interpretation of the experimental results, a metabolically structured model has been set up. This model adequately describes the observed kinetics of the poly(β‐hydroxybutyrate) formation and consumption. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 773–782, 1997.

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Linear growth and poly( -hydroxybutyrate) synthesis in response to pulse-wise addition of the growth-limiting substrate to steady-state heterotrophic continuous cultures of Aquaspirillum autotrophicum

Cited by 19 publications

References 27 publications

The effect of dissolved oxygen on PHB accumulation in activated sludge cultures

The effect of dissolved oxygen on PHB accumulation in activated sludge cultures

rRNA and Poly-β-Hydroxybutyrate Dynamics in Bioreactors Subjected to Feast and Famine Cycles

Kinetic modeling of poly(β-hydroxybutyrate) production and consumption byParacoccus pantotrophus under dynamic substrate supply

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