Comparison between different strategies for the realization of flashing-light effects – Pneumatic mixing and flashing illumination

Luzi, Giovanni; McHardy, Christopher; Lindenberger, Christoph; Rauh, Cornelia; Delgado, Antonio

doi:10.1016/j.algal.2018.101404

Cited by 17 publications

(22 citation statements)

References 49 publications

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“…A slightly different approach is based on dividing the reactor into different light zones, therefore, reducing the calculation time by avoiding computations of dark zones [5]. A more complete and sophisticated approach involves calculating the light supply of single cells moving inside the reactor by solving the full three-dimensional radiative transfer equation and the complete three-dimensional set of Navier-Stokes equations [6,7]. For the correlation between light and growth kinetics, it is ubiquitous to use simple kinetics according to Monod or extended ones by light inhibition [4,8,9].…”

Section: Introductionmentioning

confidence: 99%

A new approach for calculating microalgae culture growth based on an inhibitory effect of the surrounding biomass

Jung

McHardy

Rauh

et al. 2021

Bioprocess Biosyst Eng

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Ever since the potential of algae in biotechnology was recognized, models describing the growth of algae inside photobioreactors have been proposed. These models are the basis for the optimization of process conditions and reactor designs. Over the last few decades, models became more and more elaborate with the increase of computational capacity. Thus far, these models have been based on light attenuation due to the absorption and scattering effects of the biomass. This manuscript presents a new way of predicting the apparent growth inside photobioreactors using simple models for enzymatic kinetics to describe the reaction between photons and the photosynthetic unit. The proposed model utilizes an inhibition kinetic formula based on the surrounding biomass to describe the average growth rate of a culture, which is determined by the local light intensities inside the reactor. The result is a mixed-inhibition scheme with multiple inhibition sites. The parameters of the new kinetic equation are replaced by empirical regression functions to correlate their dependency on incident light intensity and reactor size. The calibrations of the parameters and the regression functions are based on the numerical solutions of the growth rate computed with a classical Type II model. As a final verification, we apply the new equation in predicting the growth behavior of three phototrophic organisms in reactors of three different sizes.

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Section: Introductionmentioning

confidence: 99%

A new approach for calculating microalgae culture growth based on an inhibitory effect of the surrounding biomass

Jung

McHardy

Rauh

et al. 2021

Bioprocess Biosyst Eng

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“…As the first one is key for proper batch operation given the fact that the culture evolves with time. As for the second, it has been highlighted in recent work [17] that pneumatic mixing alone cannot achieve efficient flashing light effect. Indeed it restricts average achievable light/dark cycles frequencies and prevents the use of high diameter culture vessels because of low efficiency radial mixing.…”

Section: Introductionmentioning

confidence: 99%

Multiscale numerical workflow describing microalgae motion and light pattern incidence towards population growth in a photobioreactor

Pozzobon

Perré

2020

Journal of Theoretical Biology

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In this article, a numerical workflow describing the microalgal growth inside of a photobioreactor is proposed. CFD is used to compute reactor internal hydrodynamics taking into account marine impeller rotation and sparged bubbles motion. Lagrangian approach is used to track microalgae motion inside of the culture vessel. The illumination across the reactor is obtained using the classical Beer-Lambert's law. The combination of light field and cell motion allows to reconstruct the light history of each microalgae. These histories are then supplied to Han's model which predicts individual growth rate and experienced photodamages. Once computed, several thousands of trajectories are agglomerated at the population level yielding the photobioreactor performances. After having ensured properties convergence, this procedure is applied to a large range of optical density (0 to 4.0), i.e. cell concentration, and incident light intensities (0 to 2 000 µmolPhoton/m 2 /s). From this exploration, it is possible to determine the photobioreactor response surfaces in terms of growth rate and photodamages. These are latter used to propose an optimal lighting strategy for biomass production-reducing photobioreactor operation time by 16 % compared to classical two-step procedure-and assist light induced stress with the aim of triggering secondary metabolites production.

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“…Additionally, μ s ʹ can be used to calculate growth rates in nearly real-time, enabling process monitoring even in highly concentrated suspensions. Furthermore, the determined optical parameters of algal cells can be used in future approaches to model light penetration within PBRs which is expected to be a key to enhance reactor performance [ 31 , 32 ]. Thus, there is a high potential for PDW spectroscopy to be used for advanced process monitoring, process control, and to ensure a better process understanding in concentrated biotechnological suspensions.…”

Section: Discussionmentioning

confidence: 99%

Inline monitoring of high cell density cultivation of Scenedesmus rubescens in a mesh ultra-thin layer photobioreactor by photon density wave spectroscopy

et al. 2022

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Objective Due to multiple light scattering that occurs inside and between cells, quantitative optical spectroscopy in turbid biological suspensions is still a major challenge. This includes also optical inline determination of biomass in bioprocessing. Photon Density Wave (PDW) spectroscopy, a technique based on multiple light scattering, enables the independent and absolute determination of optical key parameters of concentrated cell suspensions, which allow to determine biomass during cultivation. Results A unique reactor type, called “mesh ultra-thin layer photobioreactor” was used to create a highly concentrated algal suspension. PDW spectroscopy measurements were carried out continuously in the reactor without any need of sampling or sample preparation, over 3 weeks, and with 10-min time resolution. Conventional dry matter content and coulter counter measurements have been employed as established offline reference analysis. The PBR allowed peak cell dry weight (CDW) of 33.4 g L−1. It is shown that the reduced scattering coefficient determined by PDW spectroscopy is strongly correlated with the biomass concentration in suspension and is thus suitable for process understanding. The reactor in combination with the fiber-optical measurement approach will lead to a better process management.

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Comparison between different strategies for the realization of flashing-light effects – Pneumatic mixing and flashing illumination

Cited by 17 publications

References 49 publications

A new approach for calculating microalgae culture growth based on an inhibitory effect of the surrounding biomass

A new approach for calculating microalgae culture growth based on an inhibitory effect of the surrounding biomass

Multiscale numerical workflow describing microalgae motion and light pattern incidence towards population growth in a photobioreactor

Inline monitoring of high cell density cultivation of Scenedesmus rubescens in a mesh ultra-thin layer photobioreactor by photon density wave spectroscopy

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