Survival of the fastest: Selective removal of the side population for enhanced PHA production in a mixed substrate enrichment

Korkakaki, Emmanouela; Loosdrecht, Mark C.M. van; Kleerebezem, Robbert

doi:10.1016/j.biortech.2016.05.125

Cited by 33 publications

(21 citation statements)

References 34 publications

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“…Interestingly, the TSS at the beginning of the batch had a linear correlation with the initial PHA content of the cells (Table 5). High PHA contents are known to favor cell settlement, due to increased density (Korkakaki et al, 2016). Nonetheless, differences observed here (from 1.6-4.4 wt%) could not justify important differences in the cell density.…”

Section: Reproducibility Of the Pha Accumulationcontrasting

confidence: 68%

“…The presence of substrates which favor the channeling of carbon towards microbial growth instead of PHA accumulation is a general obstacle, as it limits the PHA content of the cells (Marang et al, 2014;Tamis et al, 2014). In a recent study, the selective consumption of VFA over methanol was achieved in an MMC enriched from aerobic sludge using a strategy based on the selective settling capacity of PHA-containing cells (Korkakaki et al, 2016). By reducing the presence of bacteria utilizing methanol, the maximum PHA storage capacity of the culture increased from 48 to 70 wt% PHA.…”

Section: Introductionmentioning

confidence: 99%

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Combined polyhydroxyalkanoates (PHA) and 1,3-propanediol production from crude glycerol: Selective conversion of volatile fatty acids into PHA by mixed microbial consortia

Burniol-Figols

Varrone

et al. 2018

Water Research

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Crude glycerol is an important by-product of the biodiesel industry, which can be converted into volatile fatty acids (VFA) and/or 1,3-propanediol (1,3-PDO) by fermentation. In this study, a selective conversion of VFA to polyhydroxyalkanoates (PHA) was attained while leaving 1,3-PDO in the supernatant by means of mixed microbial consortia selection strategies. The process showed highly reproducible results in terms of PHA yield, 0.99 ± 0.07 C PHA/C S (0.84 g COD PHA/g COD S), PHA content (76 ± 3.1 g PHA/100 g TSS) and 1,3-PDO recovery (99 ± 2.1%). The combined process had an ultimate yield from crude glycerol of 0.19 g COD PHA and 0.42 g COD 1,3-PDO per g of input COD. The novel enrichment strategy applied for selectively transforming fermentation by-products into a high value product (PHA) demonstrates the significance of the enrichment process for targeting specific bio-transformations and could potentially prove valuable for other biotechnological applications as well.

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Section: Reproducibility Of the Pha Accumulationcontrasting

confidence: 68%

Section: Introductionmentioning

confidence: 99%

Combined polyhydroxyalkanoates (PHA) and 1,3-propanediol production from crude glycerol: Selective conversion of volatile fatty acids into PHA by mixed microbial consortia

Burniol-Figols

Varrone

et al. 2018

Water Research

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“…As a whole, the average ratio of VFAs to non-VFAs -q tVFA /-q tnon-VFA was 13 in the feast phase and 6.5 in the early famine phase (from 24 h to 48 h). As reported, keeping this ratio above 5 was vital to maintain the dominance of PHA producers over non-PHA producers in the reactor 25 . Besides, the enriched MMC preferred decomposing intracellular PHA for growth and maintenance to consuming the extracellular non-VFAs after the VFAs were used up.…”

Section: Discussionmentioning

confidence: 82%

“…In addition to VFAs as the main products, the non-VFA organics (proteins and carbohydrates) and nutrients (nitrogen and phosphorus) are non-negligible in the fermented streams, and they usually exert adverse effects on PHA accumulation 24 . The non-VFAs were consumed more slowly than VFAs 10 , and they contributed mostly to growth but not PHA synthesis 25 , leading to lower PHA contents than when using pure-VFAs substrates 9 . Furthermore, the presence of non-VFAs would increase the survival of non-PHA-producing bacteria and impair the PHA synthetic ability of the enriched MMC 10 .…”

Section: Introductionmentioning

confidence: 97%

“…The sludge fermented hydrolysate is a typical VFAs-rich renewed stream that contains high levels of non-VFAs, N and P and has been widely applied to PHA production 3 , 9 . Most existing studies removed N and P from the hydrolysate before use 28 , 29 ; moreover, a supernatant discharge step was adopted immediately after the feast phase to eliminate the non-VFAs 25 . These operations inevitably increased the complexity and production costs of the overall process.…”

Section: Introductionmentioning

confidence: 99%

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Overall process of using a valerate-dominant sludge hydrolysate to produce high-quality polyhydroxyalkanoates (PHA) in a mixed culture

Hao

Wang

2017

Sci Rep

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The overall process of polyhydroxyalkanoates (PHA) production in a mixed culture fed by thermophilic fermented valerate-dominant sludge hydrolysate with high-level soluble organics (proteins and carbohydrates) and nutrients (nitrogen and phosphorus) was investigated in this study. The valerate-dominant hydrolysate was fed to enrich a PHA culture with an increasing concentration, and the enriched culture displayed a strong PHA-producing capacity under feast-famine conditions. Valerate in the feedstock was preferentially utilized over acetate and butyrate, and its uptake correlated with the production of 3-hydroxyvalerate (3HV) and 3-hydroxy-2-methylvalerate (3H2MV). The maximum PHA content (42.31%) was highest to date in a mixed culture with complex feedstock, and the PHA consisted of 3-hydroxybutyrate (3HB), 3HV, 3H2MV at 68.4, 23.7, 7.9 mmol C%. PHA production was inhibited when the nutrients exceeded a certain limit. Microbial analysis revealed that valerate-dominant feedstock caused Delftia (53%) to become the prevailing group over other PHA-producing bacteria. For long-term operation, 75% of the biomass at the end of feast phase was collected for PHA recovery, and the entire process exhibited a potential to produce 5 g PHA from 1 kg sludge. These findings indicate that the complex valerate-dominant sludge hydrolysate can be used to stably produce PHA containing high 3HV and 3H2MV.

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Structural variability, implementational irregularities in mathematical modelling of polyhydroxyalkanoates (PHAs) production—A state‐of‐the‐art review

Lhamo

Mahanty

2022

Biotech & Bioengineering

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The rate and extent of microbial polyhydroxyalkanoates (PHAs) production rely on the availability of substrates, growth of microbial biomass, and intracellular accumulation of polymer under nitrogen‐limited conditions. The dynamics of PHAs production captured through various structured or unstructured models can be extended to design an optimal feeding strategy for process intensification. Large variability in process assumptions, choices of kinetics, and model complexity is expected depending on substrate(s), microbial metabolism, and discretization of the process under consideration. This communication attempts to review the estimation of stoichiometric yield coefficients, metabolic modelling, and choices of unstructured kinetics in microbial PHA production. Implementational irregularities in parameter estimation and quality check in modelling exercises have also been reviewed. It is observed that the scope of the majority of the “modelling” studies is confined to the estimation of stoichiometric parameters with limited utility. In dynamic models, microbial growth is often described using either Monod or logistic variants, while PHAs production adopts a Luedeking–Piret expression with or without substrate inhibition. Though model selection, regression with experimental data, parameter estimation, and model validation are integral parts of the exercise, very few provide sufficient coverage on all those aspects. Application of the model to control or optimize the bioprocess has rarely been attempted.

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Survival of the fastest: Selective removal of the side population for enhanced PHA production in a mixed substrate enrichment

Cited by 33 publications

References 34 publications

Combined polyhydroxyalkanoates (PHA) and 1,3-propanediol production from crude glycerol: Selective conversion of volatile fatty acids into PHA by mixed microbial consortia

Combined polyhydroxyalkanoates (PHA) and 1,3-propanediol production from crude glycerol: Selective conversion of volatile fatty acids into PHA by mixed microbial consortia

Overall process of using a valerate-dominant sludge hydrolysate to produce high-quality polyhydroxyalkanoates (PHA) in a mixed culture

Structural variability, implementational irregularities in mathematical modelling of polyhydroxyalkanoates (PHAs) production—A state‐of‐the‐art review

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