The addition of ethanol as defoamer in fermentation of rhamnolipids

Sha, Ruyi; Meng, Qin; Jiang, Lifang

doi:10.1002/jctb.2728

Cited by 27 publications

(35 citation statements)

References 23 publications

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“…The superior demulsification ability of rhamnolipids to that of chemical surfactants like sodium dodecyl sulfate, etc. might be due to their much higher surface activity (Sha et al, 2012b), which have been suggested to benefit the breakup of the interfacial film as well as the coalescence of droplets (Kim and Wasan, 1996). In view of costefficiency, rhamnolipid at 1000 mg/L was selected for subsequent researches in demulsifying waste crude oil.…”

Section: Demulsification Of Waste Crude Oil By Rhamnolipidsmentioning

confidence: 99%

Application of rhamnolipid as a novel biodemulsifier for destabilizing waste crude oil

Long

Zhang

Shen

et al. 2013

Bioresource Technology

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101

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Section: Demulsification Of Waste Crude Oil By Rhamnolipidsmentioning

confidence: 99%

Application of rhamnolipid as a novel biodemulsifier for destabilizing waste crude oil

Long

Zhang

Shen

et al. 2013

Bioresource Technology

Self Cite

101

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“…Rhamnolipids have typically been produced by aerobic fermentation systems with high agitation and submerged sparging of fine oxygen or air bubbles [15][16][17][18]. Extensive and stable foaming occurs in such systems and causes serious operational problems such as wall growth of cells, overflow of foams, clogging of gas outlet filters, and higher chance of contamination [16,19].…”

Section: Introductionmentioning

confidence: 99%

Cells Were a More Important Foaming Factor than Free Rhamnolipids in Fermentation of Pseudomonasaeruginosa E03‐40 for High Rhamnolipid Production

Sodagari

2013

J Surfact & Detergents

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Rhamnolipids are among the best‐known biosurfactants. Severe foaming occurs in aerobic rhamnolipid fermentation and negatively affects operation and economics of the biosurfactant production. In this study the foaming properties were examined with samples taken along a Pseudomonas aeruginosa fermentation that produced 55 g l−1 rhamnolipids with a maximum volumetric productivity of 0.080 g l−1 h−1 and a maximum specific productivity of 0.013 g g−1 h−1. For a better understanding of the process, the broth samples were also centrifuged to prepare cell‐free supernatants and cell suspensions in water, and all samples were evaluated under fixed foaming conditions. In addition to the time profiles of foam rise, the initial foaming rates and maximum foam volumes were determined. Contrary to the general assumption, the cells, not rhamnolipids, were the main foaming agents in the fermentation. Soluble components including rhamnolipids had secondary roles. Supernatant foaming was higher after the culture entered the rhamnolipid‐producing stationary phase; however, the foaming appeared to decrease with increasing rhamnolipid concentrations at high concentrations (>15 g l−1). The pH effects on foaming of broths, supernatants, and cell suspensions were also studied. Broth foaming was 55 and 80 % less at pH 5.5 and 5.0, respectively, compared to that at pH 6.5. Cell growth and rhamnolipid production at lower pH should be included in future studies. In addition, strain selection or genetic engineering and medium modification to reduce cell hydrophobicity are suggested as useful strategies to address the foaming issue of rhamnolipid fermentation.

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“…The supernatant was taken for measuring rhamnolipid content using the anthrone-sulfuric assay [26] while the sediment was suspended in deionized water for detecting the cell content. The absorbance was then measured at 650 nm using water as a blank [27]. Optical density (OD 650 ) was converted to the cell concentration by a standard curve.…”

Section: Rhamnolipid Fermentationmentioning

confidence: 99%

Mechanism Study on the Severe Foaming of Rhamnolipid in Fermentation

Long

Sha

Meng

et al. 2016

J Surfact & Detergents

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Although the biosurfactant rhamnolipid has been previously characterized as having low foam ability, its fermentation is largely impeded by severe foaming. Hence, the investigation of this paradox is critically important for improving the mass production of rhamnolipid. Unexpectedly, the hydrophobic cell, instead of rhamnolipid, has been claimed to explain such severe foaming in rhamnolipid fermentation. This study tried to systematically investigate the severe foaming in fermentation, aiming to propose an effective strategy for foam control. The overflowing foam sustained a super high stability in terms of half‐time for over 30 min. The major product of rhamnolipid largely contributed to the severe foaming in the fermentation process whereas other products like cells elicited much more limited effects. Furthermore, the foam stability of the fermentation broth increased with rhamnolipid concentration and noticeably increased with agitation speed. In the classic Bikerman foam test system without stirring, rhamnolipid showed foam stability as low as Tween 20 which is well known for its poor foam stability. However, in a stirring Bikerman system, rhamnolipid exhibited a foam stability almost as high as sodium dodecyl sulfate (SDS) at 10 g/L and even surpassed SDS at a higher concentration of 20 g/L. Hence, the extraordinarily increased foam stability of rhamnolipid with both agitation and concentration could explain the severe foaming at its late‐stage fermentation when rhamnolipid‐rich solution is mechanically agitated.

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The addition of ethanol as defoamer in fermentation of rhamnolipids

Cited by 27 publications

References 23 publications

Application of rhamnolipid as a novel biodemulsifier for destabilizing waste crude oil

Application of rhamnolipid as a novel biodemulsifier for destabilizing waste crude oil

Cells Were a More Important Foaming Factor than Free Rhamnolipids in Fermentation of Pseudomonasaeruginosa E03‐40 for High Rhamnolipid Production

Mechanism Study on the Severe Foaming of Rhamnolipid in Fermentation

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