Rheology of filamentous fermentations

Olsvik, E. S.; Kristiansen, B.

doi:10.1016/0734-9750(94)90288-7

Cited by 86 publications

(64 citation statements)

References 82 publications

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“…This full model output provides important monitoring information to operators, in particular the viscosity measurements, which are of high importance in industrial filamentous fungal processes (Olsvik and Kristiansen, 1994).…”

Section: Accepted Preprintmentioning

confidence: 99%

Application of a mechanistic model as a tool for on‐line monitoring of pilot scale filamentous fungal fermentation processes—The importance of evaporation effects

Mears

Stocks

Albæk

et al. 2016

Biotech & Bioengineering

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A mechanistic model-based soft sensor is developed and validated for 550L filamentous fungus fermentations operated at Novozymes A/S. The soft sensor is comprised of a parameter estimation block based on a stoichiometric balance, coupled to a dynamic process model. The on-line parameter estimation block models the changing rates of formation of product, biomass, and water, and the rate of consumption of feed using standard, available online measurements. This parameter estimation block, is coupled to a mechanistic process model, which solves the current states of biomass, product, substrate, dissolved oxygen and mass, as well as other process parameters including k L a, viscosity and partial pressure of CO 2 .State estimation at this scale requires a robust mass model including evaporation, which is a factor not often considered at smaller scales of operation.The model is developed using a historical dataset of eleven batches from the fermentation pilot plant (550L) at Novozymes A/S. The model is then implemented on-line in 550L fermentation processes operated at Novozymes A/S in order to validate the state estimator model on fourteen new batches utilizing a new strain. The product concentration in the validation batches was predicted with an average root mean sum of squared error (RMSSE) of 16.6%. In addition, calculation of the Janus coefficient for the validation batches shows a suitably calibrated model. The robustness of the model prediction is assessed with respect to the accuracy of the input data. Parameter estimation uncertainty is also carried out. The application of this on-line state estimator allows for on-line monitoring of pilot scale batches, including real-time estimates of multiple parameters which are not able to be monitored online. With successful application of a soft sensor at this scale, this allows for improved process monitoring, as well as opening up further possibilities for on-line control algorithms, utilizing these on-line model outputs. This article is protected by copyright. All rights reserved

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Section: Accepted Preprintmentioning

confidence: 99%

Application of a mechanistic model as a tool for on‐line monitoring of pilot scale filamentous fungal fermentation processes—The importance of evaporation effects

Mears

Stocks

Albæk

et al. 2016

Biotech & Bioengineering

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“…In the cases where large clumps are formed, the viscosity of the cultivation liquid is increased, resulting in reduced oxygen mass transfer and an increased fraction of oxygen-limited cells, as well as a decreased productivity and/or production of undesirable metabolites. Although filamentous fungi have been used in the fermentation industry for many years, the high cultivation viscosity is still a major unresolved problem (17,22), and it makes a filamentous-fungal cultivation more difficult to aerate than single-cell cultivation with the same biomass concentration. Our findings for the ChsB/G (chsB disruption) strain show that it has an altered submerged morphology compared to the wild type; the strain is less prone to form large inseparable clumps (Fig.…”

Section: Involvement Of Csma In Branchingmentioning

confidence: 99%

Metabolic Engineering of the Morphology of Aspergillus oryzae by Altering Chitin Synthesis

Müller

McIntyre

Hansen

et al. 2002

Appl Environ Microbiol

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Morphology and ␣-amylase production during submerged cultivation were examined in a wild-type strain (A1560) and in strains of Aspergillus oryzae in which chitin synthase B (chsB) and chitin synthesis myosin A (csmA) have been disrupted (ChsB/G and CM101). In a flowthrough cell, the growth of submerged hyphal elements was studied online, making it possible to examine the growth kinetics of the three strains. The average tip extension rates of the CM101 and ChsB/G strains were 25 and 88% lower, respectively, than that of the wild type. The branching intensity in the CM101 strain was 25% lower than that in the wild type, whereas that in the ChsB/G strain was 188% higher. During batch cultivation, inseparable clumps were formed in the wild-type strain, while no or fewer large inseparable clumps existed in the cultivations of the ChsB/G and CM101 strains. The ␣-amylase productivity was not significantly different in the three strains. A strain in which the transcription of chsB could be controlled by the nitrogen source-regulated promoter niiA (NiiA1) was examined during chemostat cultivation, and it was found that the branching intensity could be regulated by regulating the promoter, signifying an important role for chsB in branching. However, the pattern of branching responded very slowly to the change in transcription, and increased branching did not affect ␣-amylase productivity. ␣-Amylase residing in the cell wall was stained by immunofluorescence, and the relationship between tip number and enzyme secretion is discussed.Filamentous fungi, such as Aspergillus oryzae, are widely used for industrial enzyme production, since they are able to secrete large amounts of proteins (e.g., amylases, proteases, phytases, and lipases) into the medium. Filamentous fungi grow by hyphal extension and branching through processes that are regulated in a way that is still not completely understood. During submerged cultivation, the growing hyphal elements tend to entangle, and this affects the rheology of the cultivation medium and the mixing characteristics in an undesirable fashion. This results in poor mixing and poor mass transfer of the substrate, and it makes the morphologies of filamentous fungi an obvious, yet unanswered, challenge in process optimization. Recently, however, there have been major advances in the tools available for metabolic engineering of aspergilli (reviewed by McIntyre et al. [17]), such as developments in genomics, the increased number of suitable transformation vectors, and powerful image analysis tools that enable rapid quantification of the fungal morphology. This has made metabolic engineering of the morphology for process optimization possible.Metabolic engineering of morphology requires detailed knowledge of the relationships among productivity, growth, and morphology. The morphologies of filamentous organisms can be classified into macroscopic and microscopic morphologies (21), and techniques for analyzing morphology on both of these levels have advanced rapidly during the last decade (reviewed...

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“…Van't [4] model for water, ( ) Present study for distilled water, ( ): Van't [4] model for electrolyte salt, ( ): Linek et al [7] model for electrolyte salt, ( ): Present study for electrolyte salt and (ο): Linek et al [7] model for three Rushton turbines in electrolytes salt As for open type stirrers, Van't [4] generalized correlations are well established for non-viscous fluid systems while Linek et al [7] correlated k L a specifically for 0.5 M Na 2 SO 4 system. Most correlations on oxygen transfer for viscous pseudoplastic CMC lack the level variation of apparent viscosity due to anomalous rheological nature of simulant media with the agitator shearing rate [3,15,20] . As such, there is conspicuous omission of η a term in the collection of k L a models for Rushton turbine listed in Table 4.…”

Section: Discussionmentioning

confidence: 99%

“…Improvement was made through the inclusion of apparent viscosity (η a ) term into Eq. 1 [20] . Design Expert software (version 6.0.6, Stat Ease, USA) was used to simulate the predictive k L a model for the three different fluid systems.…”

Section: Modeling Of Correlationsmentioning

confidence: 99%

Modeling of Oxygen Transfer Correlations for Stirred Tank Bioreactor Agitated with Atypical Helical Ribbon Impeller

Moh¹,

Mohamad²,

Ramanan³

et al. 2009

American J. of Applied Sciences

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Problem Statement: Mixing filamentous fungi entails delicate balance between promoting high volumetric oxygen transfer coefficient (k L a) while keeping low hydrodynamic stresses in the microenvironment of cultures. This study examined the oxygen transfer capability of a prototype low shear helical impeller as a potential replacement for the standard Rushton turbine. Approach: The dependence of k L a upon specific power uptake, superficial gas velocity and apparent viscosity were examined under coalescent, non-coalescent and viscous pseudoplastic fluids scenario using dynamic gassing out technique. Subsequently, collected data were treated under historical data design of response surface methodology. Results: Three empirical power law k L a correlations were developed for each fluid. Correlation comparison with literature models for single turbine agitation suggest higher k L a augmentation within 1.5-3.6 folds for helical impeller in distilled water and as high as 78% improvement in electrolytes fluid. However impeller performance is comparatively 10% lower against theoretical k L a of triple turbines arrangement for power uptake between 0-1600 W m -3 . In case of carboxymethylcellulose, better oxygen transfer is expected for design with higher proportionality of impeller-to-tank internal diameter. Conclusions: Helical impeller performance as gas-liquid contactor is comparable to single and triple Rushtons turbines, with superficial gas velocity proved to be more influential than power uptake in non-viscous liquids and vice versa in viscous pseudoplastic fluids.

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Rheology of filamentous fermentations

Cited by 86 publications

References 82 publications

Application of a mechanistic model as a tool for on‐line monitoring of pilot scale filamentous fungal fermentation processes—The importance of evaporation effects

Application of a mechanistic model as a tool for on‐line monitoring of pilot scale filamentous fungal fermentation processes—The importance of evaporation effects

Metabolic Engineering of the Morphology of Aspergillus oryzae by Altering Chitin Synthesis

Modeling of Oxygen Transfer Correlations for Stirred Tank Bioreactor Agitated with Atypical Helical Ribbon Impeller

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