The Role of Cell Hydrophobicity in the Formation of Aerobic Granules

Liu, Yu; Yang, Shu-Fang; Liu, Qi-Shan; Tay, Joo‐Hwa

doi:10.1007/s00284-002-3878-3

Cited by 87 publications

(40 citation statements)

References 16 publications

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“…In this study, the cell surface hydrophobicity rates slightly increased with the incubation time from approximately 0.5% to 8.5% Ϯ 5.5% and 8.3% Ϯ 4.6% for C 16 and C 24 cultures, respectively, compared to approximately 4% in the control without any hydrocarbon. In contrast, the hydrophobicity rate in C 36 cultures could be as high as 23.9% Ϯ 3.7% (Fig.…”

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confidence: 85%

“…S1 in the supplemental material); this finding suggested that shorter alkanes resulted in a higher emulsifying activity, which allowed cells to access alkanes more easily. The C 16 , C 24 , and C 36 culture broths yielded 95.7, 25.4, and 15.8 mg liter Ϫ1 of crude biosurfactant, respectively. Among them, 2 glycolipid compounds (16-A and 16-B) (Fig.…”

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confidence: 99%

“…However, strain DQ12-45-1b could produce all the 3 types in various amounts when C 16 , C 24 , and C 36 were used as the sole carbon sources. Moreover, the simultaneous detection of different glycolipids, both with different saccharide and acid moieties, in a Dietzia strain has not been reported before.…”

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confidence: 99%

“…Strain DQ12-45-1b could degrade C 16 , C 24 , and C 36 n-alkanes for growth (see Table S1 in the supplemental material), as was previously reported (19,20). Along with the growth and degradation of alkanes, the surface tension of the culture broth decreased from approximately 62 mN m Ϫ1 to 27.78 Ϯ 1.97 and 45.97 Ϯ 2.19 mN m Ϫ1 at day 30 for C 16 and C 24 cultures, respectively, and to 48.66 Ϯ 0.51 mN m Ϫ1 at day 45 for the C 36 culture (see Fig.…”

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confidence: 99%

“…The hydrophobicity of the cell surface, which is measured as the surface hydrophobicity rate, plays an important role in the microbial attachment onto other hydrophobic surfaces, such as solid n-alkanes (24). In this study, the cell surface hydrophobicity rates slightly increased with the incubation time from approximately 0.5% to 8.5% Ϯ 5.5% and 8.3% Ϯ 4.6% for C 16 and C 24 cultures, respectively, compared to approximately 4% in the control without any hydrocarbon.…”

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n -Alkane Chain Length Alters Dietzia sp. Strain DQ12-45-1b Biosurfactant Production and Cell Surface Activity

Wang

Nie

Tang

et al. 2013

Appl Environ Microbiol

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c Upon growth on n-hexadecane (C 16 ), n-tetracosane (C 24 ), and n-hexatriacontane (C 36 ), Dietzia sp. strain DQ12-45-1b could produce different glycolipids, phospholipids, and lipopeptides. Interestingly, cultivation with C 36 increased cell surface hydrophobic activity, which attenuated the negative effect of the decline of the emulsification activity. These results suggest that the mechanisms of biosurfactant production and cell surface hydrophobicity are dependent upon the chain lengths of the n-alkanes used as carbon sources. Recently, the biodegradation of crude oil constituents, such as alkanes, through bioremediation of oil-polluted environments (1-3) and microbial enhanced oil recovery (MEOR) technology (4) has received worldwide attention. To date, a number of microorganisms have been reported to degrade alkanes of different chain lengths (5). A critical step in the biodegradation process requires microorganisms to access hydrophobic alkanes by at least two possible mechanisms. First, microorganisms produce surface-active materials, including glycolipids, phospholipids, and lipopeptides, to emulsify alkanes and achieve surfactant-mediated access (6-12). Second, they increase the hydrophobic activity of the cell surface to directly interact with alkanes (5, 13).Although extensive research has been conducted on the production of different biosurfactants and the cell surface hydrophobic activities, these studies were mainly restricted to alkanes with chain lengths shorter than 18 carbon atoms (C 18 ) (14-18). This raises the question of how bacteria, such as those belonging to the genus Dietzia, access hydrocarbons with chain lengths longer than C 18 . It is unclear whether accessing longer alkanes requires the production of surface-active materials that are similar to those produced when shorter alkanes (i.e., ϽC 18 ) are degraded. In addition, whether cell surface hydrophobicity contributes to the accession of longer alkanes is unknown. The aim of this study was, therefore, to address these questions because degradation of alkanes longer than C 18 is important for effective MEOR and bioremediation. We used a broad-spectrum alkane-degrading Dietzia sp. strain, 20), and the results of our study revealed that biosurfactant production and cell surface hydrophobic activity changed when different-chain-length n-alkanes were used as the sole carbon sources.After Dietzia sp. strain DQ12-45-1b was incubated in mineral salt medium (MSM) (21) amended with 0.3% (vol/vol) n-hexadecane (C 16 ) and 0.05% (wt/vol) n-tetracosane (C 24 ) and n-hexatriacontane (C 36 ) as the sole carbon sources, respectively, the cultures were sampled at different time points and analyzed for bacterial growth, alkane degradation, cell surface hydrophobic activities, and emulsifying capacity of the culture broth. The biosurfactants were also extracted from the culture broth, and the moieties of the glycolipid-like biosurfactant were additionally analyzed. The transcripts of the glycolipid synthesis-related genes were also analyzed by rea...

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confidence: 85%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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n -Alkane Chain Length Alters Dietzia sp. Strain DQ12-45-1b Biosurfactant Production and Cell Surface Activity

Wang

Nie

Tang

et al. 2013

Appl Environ Microbiol

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Understanding the properties of aerobic sludge granules as hydrogels

Seviour

Pijuan

Nicholson

et al. 2008

Biotech & Bioengineering

114

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Aerobic sludge granules are larger, denser microbial aggregates than activated sludge flocs with a smoother and more regular surface, which facilitates greater wastewater treatment intensity. Factors important in their growth are still poorly understood, which is an impediment to the construction and operation of full-scale aerobic sludge granule processes. Data in this article obtained with granules treating an abattoir wastewater provide evidence that aerobic sludge granules are hydrogels. The results also demonstrate a method for characterizing macromolecular associations. The rheological profile of these granules was found to be analogous with that of typical polymer gels. Water uptake or swelling reflects an equilibrium between granule elastic modulus and osmotic pressure, whereby uptake is increased by reducing solute concentration or the elastic modulus. A weakening of the extracellular polymeric substance (EPS) matrix as demonstrated with mechanical spectroscopy was induced by several environmental factors including temperature, pH and ionic strength. Uniform and elastic deformation was observed at low strain. Enzymatic degradation studies indicate that proteins and alpha-polysaccharides were the major granule structural materials. The aerobic sludge granules in the current study were therefore protein-polysaccharide composite physical hydrogels. While aerobic sludge granules treating an abattoir wastewater are used as a case study, many of the fundamental principles detailed here are relevant to other granulation processes. The paradigm established in this study can potentially be applied to better understand the formation of aerobic sludge granules and thus overcome a hurdle in the acceptance of aerobic sludge granulation as an alternative to more traditional wastewater treatment processes.

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Aerobic granular treatment of 2,4‐dichlorophenol

Khan

Sabir

2011

Can J Chem Eng

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2,4-Dichlorophenol (2,4-DCP) fed aerobic granules were cultivated in a sequencing batch reactor (SBR). Stable and compact granules were obtained in 60 days of SBR operation. Formed granules were compact and strong with closed packed channels. After granulation, effluent chemical oxygen demand and 2,4-DCP concentrations were 95 and 2.5 mg L −1 with corresponding removal efficiencies of 96% and 95% were achieved. Degradation profile shows a high initial degradation rate which decreases later. Degradation rate was found to be directly proportional to the substrate concentration. Specific degradation rate of 2,4-DCP was 6.54 mg 2,4-DCP gVSS −1 h −1 at 60 mg L −1 and specific cell growth rate was 0.042 ± 0.02 day −1 . High optical density (OD 600 ) the system shows effective retention of biomass which is the main advantage of present technique.Des granules aérobies ontété cultivés avec succès pour la dégradation du 2,4-DCP. Des granules stables et compacts ontété obtenus après 70 jours d'opérations en réacteurà séquencement et par lots. Des efficiences de demande chimique finale en oxygène et d'élimination de 2,4-DCP s'élevantà 96% et 95% ontété atteintes. Le profil de dégradation montre que le taux de dégradationétait initialementélevé mais qu'il ralentit plus tard. On a observé une bonne correspondance entre la demande chimique en oxygène et le profil d'élimination de 2,4-DCP. Le taux de dégradation est directement proportionnelà la concentration de substrat. Le taux spécifique de dégradation de 2,4-DCPétait de 6.54 mg de 2,4-DCP gVSS −1 L −1 h −1à 60 mg L −1 et le taux spécifique de croissance cellulaireétait de 0.042 ± 0.02 day −1 . Une haute densité optique du réacteurà séquencement et par lots montre une rétention de la biomasse effective, ce qui est l'avantage principal de cette technique.

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The Role of Cell Hydrophobicity in the Formation of Aerobic Granules

Cited by 87 publications

References 16 publications

n -Alkane Chain Length Alters Dietzia sp. Strain DQ12-45-1b Biosurfactant Production and Cell Surface Activity

n -Alkane Chain Length Alters Dietzia sp. Strain DQ12-45-1b Biosurfactant Production and Cell Surface Activity

Understanding the properties of aerobic sludge granules as hydrogels

Aerobic granular treatment of 2,4‐dichlorophenol

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