Study of drop and bubble sizes in a simulated mycelial fermentation broth of up to four phases

Galindo, Enrique; Pacek, Andrzej W.; Nienow, Alvin W.

doi:10.1002/(sici)1097-0290(20000720)69:2<213::aid-bit10>3.0.co;2-d

Cited by 53 publications

(23 citation statements)

References 22 publications

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“…(3), it can be seen that the presence of the organic fraction in the absence of surfactant improves k L a, particularly at high stirring rates. This effect has been attributed to the decrease of bubble diameter and consequently gas hold-up increase due to the oil addition [23], which consequently increases the interfacial area for the gas-liquid mass transfer. Previous work [9] suggests that interfacial properties of the organic phase have more influence in the behaviour of gas-liquid-liquid systems than the hydrodynamic effects, since P g can be assumed independent of oil fraction.…”

Section: Effect Of the Biphasic Medium On K L A Valuesmentioning

confidence: 99%

Oxygen mass transfer in a biphasic medium: Influence on the biotransformation of methyl ricinoleate into γ-decalactone by the yeast Yarrowia lipolytica

Gomes

Aguedo

Teixeira

et al. 2007

Biochemical Engineering Journal

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In this work, an empirical correlation is proposed to describe k L a as a function of operating conditions (agitation and aeration rates) and of oil and surfactant volumetric fractions in a biotransformation medium, an oil-in-water dispersion. An interaction effect between the oil and the surfactant effects was found, since oil presence increased k L a in the absence of the surfactant but had an opposite effect when Tween 80 was available in the medium. The biotransformation of methyl ricinoleate (MR) into ␥-decalactone (an aroma compound of industrial interest), by the yeast Yarrowia lipolytica, was carried out at different conditions of operation, to evaluate the influence of k L a on the production of the aroma. It was demonstrated that k L a had an influence on the aroma production; however, for the low hydrophobic substrate concentration used (1.08% v/v) and cellular density of 2.0 × 10 7 cells mL −1 , a minimal k L a value of 70 h −1 was necessary to attain the maximal aroma production.

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Section: Effect Of the Biphasic Medium On K L A Valuesmentioning

confidence: 99%

Oxygen mass transfer in a biphasic medium: Influence on the biotransformation of methyl ricinoleate into γ-decalactone by the yeast Yarrowia lipolytica

Gomes

Aguedo

Teixeira

et al. 2007

Biochemical Engineering Journal

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show abstract

“…In addition, particles do not transmit light as bubbles do. In one application, acceptable bubble images (i.e., objects with dark edges and a shiny middle) and an indication of dispersed biomass between bubbles were obtained only up to 5 g/L biomass dry cell weight [27]. Reflection from stainless steel tank internals (i.e., impeller, agitator shaft, sparger) can also interfere, resulting in bright blotches which are reduced in the presence of medium and cells.…”

Section: Measurement Interferencesmentioning

confidence: 99%

“…Common plots are (1) the percentage number frequency (either incremental or cumulative) or number probability density (Y axis) versus (2) the bubble diameter in a specified range [27] or versus the number of bubbles less than the stated bubble size (X axis) [59]. Selection of size ranges or ''bins'' directly affects the accuracy of the distribution's calculated parameters and obviously cannot be less than the established incremental size measurement range of the instrument.…”

Section: Presentation and Analysis Of Bubble Size Distribution Datamentioning

confidence: 99%

Measurement of bubble and pellet size distributions: past and current image analysis technology

Junker

2006

Bioprocess Biosyst Eng

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Measurements of bubble and pellet size distributions are useful for biochemical process optimizations. The accuracy, representation, and simplicity of these measurements improve when the measurement is performed on-line and in situ rather than off-line using a sample. Historical and currently available measurement systems for photographic methods are summarized for bubble and pellet (morphology) measurement applications. Applications to cells, mycelia, and pellets measurements have driven key technological developments that have been applied for bubble measurements. Measurement trade-offs exist to maximize accuracy, extend range, and attain reasonable cycle times. Mathematical characterization of distributions using standard statistical techniques is straightforward, facilitating data presentation and analysis. For the specific application of bubble size distributions, selected bioreactor operating parameters and physicochemical conditions alter distributions. Empirical relationships have been established in some cases where sufficient data have been collected. In addition, parameters and conditions with substantial effects on bubble size distributions were identified and their relative effects quantified. This information was used to guide required accuracy and precision targets for bubble size distribution measurements from newly developed novel on-line and in situ bubble measurement devices.

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“…The emulsion is a distribution of oil drops of different sizes dispersed into the aqueous medium. The mean drop size of oil in an oil-water emulsion correlates positively with approximately the square root of oil-water interfacial tension, the mixing intensity, and the volume fraction of the dispersed phase (10,37), which in the case of our PG201 liquid cultures would be 0.002. For chlorobenzene in water (interfacial tension of 0.0334 N/m), where the volume fraction of chlorobenzene was 0.005 and the stirring rate was 180 min Ϫ1 , the mean oil droplet diameter was 215 m (37).…”

Section: Discussionmentioning

confidence: 75%

Assessing the Role of Pseudomonas aeruginosa Surface-Active Gene Expression in Hexadecane Biodegradation in Sand

Holden

LaMontagne

Bruce

et al. 2002

Appl Environ Microbiol

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Low pollutant substrate bioavailability limits hydrocarbon biodegradation in soils. Bacterially produced surface-active compounds, such as rhamnolipid biosurfactant and the PA bioemulsifying protein produced by Pseudomonas aeruginosa, can improve bioavailability and biodegradation in liquid culture, but their production and roles in soils are unknown. In this study, we asked if the genes for surface-active compounds are expressed in unsaturated porous media contaminated with hexadecane. Furthermore, if expression does occur, is biodegradation enhanced? To detect expression of genes for surface-active compounds, we fused the gfp reporter gene either to the promoter region of pra, which encodes for the emulsifying PA protein, or to the promoter of the transcriptional activator rhlR. We assessed green fluorescent protein (GFP) production conferred by these gene fusions in P. aeruginosa PG201. GFP was produced in sand culture, indicating that the rhlR and pra genes are both transcribed in unsaturated porous media. Confocal laser scanning microscopy of liquid drops revealed that gfp expression was localized at the hexadecane-water interface. Wild-type PG201 and its mutants that are deficient in either PA protein, rhamnolipid synthesis, or both were studied to determine if the genetic potential to make surface-active compounds confers an advantage to P. aeruginosa biodegrading hexadecane in sand. Hexadecane depletion rates and carbon utilization efficiency in sand culture were the same for wild-type and mutant strains, i.e., whether PG201 was proficient or deficient in surfactant or emulsifier production. Environmental scanning electron microscopy revealed that colonization of sand grains was sparse, with cells in small monolayer clusters instead of multilayered biofilms. Our findings suggest that P. aeruginosa likely produces surface-active compounds in sand culture. However, the ability to produce surface-active compounds did not enhance biodegradation in sand culture because well-distributed cells and well-distributed hexadecane favored direct contact to hexadecane for most cells. In contrast, surface-active compounds enable bacteria in liquid culture to adhere to the hexadecane-water interface when they otherwise would not, and thus production of surface-active compounds is an advantage for hexadecane biodegradation in well-dispersed liquid systems.Natural biological attenuation is the present strategy for remediating greater than 25% of soil sites contaminated with petroleum hydrocarbons (33). Because of insufficient knowledge about in situ controls on bioavailability and biodegradation of low-solubility hydrocarbon pollutants in soil, it is difficult to predict cleanup end points (33) and to select appropriate remediation strategies. Reported mechanisms for bacterial metabolism of sparingly soluble hydrocarbons are (i) dissolution and diffusion of dissolved hydrocarbons to cells with uptake via active or passive transmembrane transport, (ii) invagination of hydrocarbon non-aqueous-phase liquid (NAPL) into cells ...

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Study of drop and bubble sizes in a simulated mycelial fermentation broth of up to four phases

Cited by 53 publications

References 22 publications

Oxygen mass transfer in a biphasic medium: Influence on the biotransformation of methyl ricinoleate into γ-decalactone by the yeast Yarrowia lipolytica

Oxygen mass transfer in a biphasic medium: Influence on the biotransformation of methyl ricinoleate into γ-decalactone by the yeast Yarrowia lipolytica

Measurement of bubble and pellet size distributions: past and current image analysis technology

Assessing the Role of Pseudomonas aeruginosa Surface-Active Gene Expression in Hexadecane Biodegradation in Sand

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