Turbulent breakage of filamentous bacteria in mechanically agitated batch culture

Heydarian, Seyed Mohammad; Ison, A. P.; Lilly, M. D.; Shamlou, P. Ayazi

doi:10.1016/s0009-2509(99)00449-2

Cited by 11 publications

(7 citation statements)

References 41 publications

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“…1.4). Especially the water swirls, or eddies, which arise under turbulent flow velocities, stretch hyphae in opposite direction with fragmentation as a logical result (Ayazi Shamlou et al, 1994;Heydarian, Ison, Lilly, & Ayazi Shamlou, 2000). Especially the water swirls, or eddies, which arise under turbulent flow velocities, stretch hyphae in opposite direction with fragmentation as a logical result (Ayazi Shamlou et al, 1994;Heydarian, Ison, Lilly, & Ayazi Shamlou, 2000).…”

Section: Fragmentationmentioning

confidence: 99%

Morphogenesis of Streptomyces in Submerged Cultures

Dissel

Claessen

Wezel

2014

Advances in Applied Microbiology

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Members of the genus Streptomyces are mycelial bacteria that undergo a complex multicellular life cycle and propagate via sporulation. Streptomycetes are important industrial microorganisms, as they produce a plethora of medically relevant natural products, including the majority of clinically important antibiotics, as well as a wide range of enzymes with industrial application. While development of Streptomyces in surface-grown cultures is well studied, relatively little is known of the parameters that determine morphogenesis in submerged cultures. Here, growth is characterized by the formation of mycelial networks and pellets. From the perspective of industrial fermentations, such mycelial growth is unattractive, as it is associated with slow growth, heterogeneous cultures, and high viscosity. Here, we review the current insights into the genetic and environmental factors that determine mycelial growth and morphology in liquid-grown cultures. The genetic factors include cell-matrix proteins and extracellular polymers, morphoproteins with specific roles in liquid-culture morphogenesis, with the SsgA-like proteins as well-studied examples, and programmed cell death. Environmental factors refer in particular to those dictated by process engineering, such as growth media and reactor set-up. These insights are then integrated to provide perspectives as to how this knowledge can be applied to improve streptomycetes for industrial applications.

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Section: Fragmentationmentioning

confidence: 99%

Morphogenesis of Streptomyces in Submerged Cultures

Dissel

Claessen

Wezel

2014

Advances in Applied Microbiology

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“…The assumption of such low viscosity during fungal fermentation may be invalid. Very recently, others have accounted for high broth viscosity during ®lamentous bacterial fermentations and found much larger values of k (Heydarian et al, 2000;Large et al, 1998). For example, a ®lamentous bacterial fermentation was recently reported to have microscale values of approximately 350 lm throughout the entire process (Large et al, 1998).…”

Section: Microscale Characterizationmentioning

confidence: 99%

Estimation of hyphal tensile strength in production‐scale Aspergillus oryzae fungal fermentations

Shukla

Wenger

et al. 2002

Biotech & Bioengineering

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Fragmentation of filamentous fungal hyphae depends on two phenomena: hydrodynamic stresses, which lead to hyphal breakage, and hyphal tensile strength, which resists breakage. The goal of this study was to use turbulent hydrodynamic theory to develop a correlation that allows experimental data of morphology and hydrodynamics to be used to estimate relative (pseudo) tensile strength (sigma(pseudo)) of filamentous fungi. Fed-batch fermentations were conducted with a recombinant strain of Aspergillus oryzae in 80 m(3) fermentors, and measurements were made of both morphological (equivalent hyphal length, L) and hydrodynamic variables (specific power input, epsilon; kinematic viscosity, v). We found that v increased over 100-fold during these fermentations and, hence, Kolmogorov microscale (lambda) also changed significantly with time. In the impeller discharge zone, where hyphal fragmentation is thought to actually take place, lambda was calculated to be 700-3500 microm, which is large compared to the size of typical fungal hyphae (100-300 microm). This result implies that eddies in the viscous subrange are responsible for fragmentation. Applying turbulent theory for this subrange, it was possible to calculate sigma(pseudo)from morphological and hydrodynamic measurements. Pseudo tensile strength was not constant but increased to a maximum during the first half and then decreased during the second half of each fermentation, presumably due to differences in physiological state. When a literature correlation for hyphal fragmentation rate (k(frag)) was modified by adding a term to account for viscosity and tensile strength, the result was better qualitative agreement with morphological data. Taken together, these results imply hyphal tensile strength can change significantly over the course of large-scale, fed-batch fungal fermentations and that existing fragmentation and morphology models may be improved if they accounted for variations in hyphal tensile strength with time.

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“…It is well known that the increase in agitation speed in bioreactor induce fragmentation of mycelial micro‐organisms due to they are sensitive to energy dissipation rate given by the impellers and in consequence the morphology is predominantly small pellets and free mycelia (Heydarian et al . ; Rocha‐Valadez et al . ).…”

Section: Discussionmentioning

confidence: 99%

“…In the bioreactor, at k L a of 47Á1 and 63Á6 h À1 , the biomass diminished after maximum dry weight was reached; nevertheless, in shake flask, this did not occur. It is well known that the increase in agitation speed in bioreactor induce fragmentation of mycelial micro-organisms due to they are sensitive to energy dissipation rate given by the impellers and in consequence the morphology is predominantly small pellets and free mycelia (Heydarian et al 2000;Rocha-Valadez et al 2006). In shake flasks, on orbital shaker, the maximum energy dissipation rate was found to be 10 times lower than in stirred tank reactor (Peter et al 2006) and it is reasonable to expect that at conditions normally used in laboratory in shake flasks the morphology was quite different.…”

Section: Discussionmentioning

confidence: 99%

Oxygen transfer coefficient and the kinetic parameters of exo-polygalacturonase production byAspergillus flavipesFP-500 in shake flasks and bioreactor

Sánchez¹,

Martínez-Trujillo

Osorio³

2012

Letters in Applied Microbiology

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Aims: To evaluate and compare the sensitivity of Exo-PG production and kinetic parameters of Aspergillus flavipes FP-500 to oxygen transfer condition in shake flasks and bioreactor. Methods and Results: Aspergillus flavipes FP-500 was grown on pectin as carbon source in shake flasks and bioreactor at different oxygen transfer conditions. The volumetric coefficient of oxygen transfer (k L a) was modified by changing both, the flask size/medium volume ratio and the agitation speed. Higher biomass concentration, Exo-PG activity, maximum specific growth rate and yield coefficient were obtained in bioreactor at higher k L a value. A strong correlation was found between biomass, Exo-PG activity and growth-associated product coefficient to k L a in bioreactor but does not in shake flasks. The mathematical model provided a good description of growth, pectin consumption and Exo-PG production in submerged batch cultures carried out in bioreactor. Conclusions: Biomass concentration, Exo-PG activity and their kinetics of Aspergillus flavipes FP-500 were strongly influenced by oxygen transfer condition and cultivation system. Significance and Impact of Study: The production of enzymes by fungal fermentation is strictly aerobic and understanding the influence of oxygen transfer condition on the production kinetic is of vital importance in order to design, optimize and translate bioprocesses to industrial scale.

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Turbulent breakage of filamentous bacteria in mechanically agitated batch culture

Cited by 11 publications

References 41 publications

Morphogenesis of Streptomyces in Submerged Cultures

Morphogenesis of Streptomyces in Submerged Cultures

Estimation of hyphal tensile strength in production‐scale Aspergillus oryzae fungal fermentations

Oxygen transfer coefficient and the kinetic parameters of exo-polygalacturonase production byAspergillus flavipesFP-500 in shake flasks and bioreactor

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