Mixing and oxygen transfer in conventional stirred fermentors

Manfredini, R.; Cavallera, V.; Marini, L.; Donati, Gianni

doi:10.1002/bit.260251224

Cited by 75 publications

(15 citation statements)

References 2 publications

(1 reference statement)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Therefore, the engineering environments of the two reactor configurations can be used to simulate the different degrees of heterogeneity observed during fermentations in large scale stirred tanks, such as the DOC gradients [14,19], demonstrating the use of the multiconfigurable airlift reactor as a scale down tool to study the impact of reactor heterogeneity.…”

Section: Discussionmentioning

confidence: 99%

Influence of a propeller on Saccharomyces cerevisiae fermentations in a pilot scale airlift bioreactor

Pollard

Ison

Shamlou

et al. 1997

Bioprocess Engineering

View full text Add to dashboard Cite

The hydrodynamics (sectional gas holdup and liquid velocities) and oxygen transfer performance of a conventionally operated multiconfigurable pilot scale (0.25 m 3 ) concentric airlift bioreactor containing baker's yeast were significantly improved by operating a marine propeller to draw liquid down the draft tube and aid recirculation at the base of the vessel. Propeller operation reduced the severe DOT heterogeneity of the reactor, which gave DOT values below 1% air saturation in the riser, by producing DOTs above 40% around the vessel at maximum energy dissipation rate. As a consequence the overall oxygen uptake rate (OUR) of the baker's yeast increased up to 3 fold with the total energy dissipation rate into the reactor until the lowest DOTs of the vessel were at or above 10%. The different degrees of heterogeneity generated by the two reactor configurations enabled the reactor to be used as a scale down tool to study the impact of heterogeneity on the physiology of fermentation broths. Comparison of the hydrodynamics and oxygen transfer between tall and short reactor heights revealed that the faster circulation times of the short reactor produced a greater improvement in the OUR with propeller operation even though similar DOT changes occurred around both sizes of reactor. This indicated that the yeast cells were responding to the rapid DOT changes around the vessel. List of symbolsA D cross sectional area of the downcomer m 2 A R cross sectional area of the riser m 2 D p propeller diameter m DCW dry cell weight g/l DOT dissolved oxygen tension % air saturation g acceleration due to gravity m/s 2 H D height of the gas -liquid dispersion from the vessel base m H DT height of the top of the draft tube from the vessel base m k L a volumetric mass transfer coefficient s -1 L clearance between the bottom of the draft tube and vessel base m N propeller speed s )1 OUR oxygen uptake rate mmol/l.h P A energy dissipation rate for airlift aeration only operation W/m 3 P g energy dissipation for airlift operation W P IN pressure at the point of gas inlet to the vessel Pa P P energy dissipation rate for propeller only operation W/m 3 P O propeller power number -P T total energy dissipation rate for combined airlift and propeller operation W/m 3 t c liquid circulation time s t m mean mixing time to achieve 90% homogeneity s U LD mean liquid linear velocity in the downcomer m/s U LR mean liquid linear velocity in the riser m/s U sg superficial gas velocity in riser m/s V L liquid volume m 3 L density of liquid kg/m 3 w density of water kg/m 3 gas holdup -D mean downcomer gas holdup -O mean overall gas holdup -R mean riser gas holdup -TS mean top section gas holdup -1 Introduction Many studies of laboratory and pilot scale [7, 10, 22, 30] airlift reactors have considered the hydrodynamics and oxygen transfer but few have examined the impact of the circulatory flow on the metabolism of fermentation cultures. For airlift operation air is introduced into one section of the vessel and bubbles are entrained into the downcomer wh...

show abstract

Section: Discussionmentioning

confidence: 99%

Influence of a propeller on Saccharomyces cerevisiae fermentations in a pilot scale airlift bioreactor

Pollard

Ison

Shamlou

et al. 1997

Bioprocess Engineering

View full text Add to dashboard Cite

show abstract

“…Their existence has been inferred from regime analysis (see Section 18-2.6) (Oosterhuis, 1984;Sweere et al, 1986) and in some cases by physical measurement (Carilli et al, 1961;Steel and Maxon, 1966;Manfredini et al, 1983;Oosterhuis andKossen, 1983, 1984). Oosterhuis and Kossen (1984) reported the existence of dissolved oxygen concentration gradients in a 25 m 3 production scale fermenter equipped with two Rushton impellers, using a low viscosity broth (refer to Figure 18-1).…”

Section: -2 Scale-up/scale-down Of Fermentation Processesmentioning

confidence: 97%

Mixing in the Fermentation and Cell Culture Industries

Amanullah¹,

Buckland²,

Nienow

2003

Handbook of Industrial Mixing

View full text Add to dashboard Cite

“…Breakthroughs have been made in hydrodynamics and mixing, modeling of two-phase gas/liquid biological processes (Guillard, 1999), large-scale microenvironment measurements (Bylund et al, 1998(Bylund et al, , 1999George, 1997;Manfredini et al, 1983;Oosterhuis and Kossen, 1984), and scale-down methodology studies (Oosterhuis et al, 1983(Oosterhuis et al, , 1985. The latter area of study includes the use of scale-down reactors (SDRs) with various biological model systems (Bylund et al, 1999;Fowler and Dunlop, 1989;George et al, 1993George et al, , 1998Larsson and Enfors, 1988;Moes et al, 1985;Neubauer et al, 1995a,b;Sweere et al, 1988a-c).…”

Section: Introductionmentioning

confidence: 97%