Inactivation combined with cell lysis of Pseudomonas putida using a low pressure carbon dioxide microbubble technology

BACKGROUND Inactivation processes can be classified into non-thermal inactivation methods such as ethylene oxide and γ-radiation, and thermal methods such as autoclaving. The ability of carbon dioxide enriched microbubbles to inactivate Pseudomonas putida suspended in physiological saline, as a non-thermal sterilisation method, was investigated in this study with many operational advantages over both traditional thermal and non-thermal sterilisation methods. RESULTS Introducing carbon dioxide enriched microbubbles can achieve ∼2-Log reduction in the bacterial population after 90 min of treatment, addition of ethanol to the inactivation solution further enhanced the inactivation process to achieve 3, 2.5 and 3.5-Log reduction for 2%, 5% and 10 %( v/v) ethanol, respectively. A range of morphological changes was observed on Pseudomonas cells after each treatment, and these changes extended from changing cell shape from rod shape to coccus shape to severe lesions and cell death. Pseudomonas putida KT 2440 was used as a model of gram-negative bacteria. CONCLUSION Using CO2 enriched microbubbles technology has many advantages such as efficient energy consumption (no heat source), avoidance of toxic and corrosive reagents, and in situ treatment. In addition, many findings from this study could apply to other gram-negative bacteria

A compartmental CFD-PBM model of high shear wet granulation

The conventional, geometrically lumped description of the physical processes inside a high shear granulator is not reliable for process design and scale-up. In this study, a compartmental Population Balance Model (PBM) with spatial dependence is developed and validated in two lab-scale high shear granulation processes using a 1.9L MiPro granulator and 4L DIOSNA granulator. The compartmental structure is built using a heuristic approach based on computational fluid dynamics (CFD) analysis, which includes the overall flow pattern, velocity and solids concentration. The constant volume Monte Carlo approach is implemented to solve the multi-compartment population balance equations. Different spatial dependent mechanisms are included in the compartmental PBM to describe granule growth. It is concluded that for both cases (low and high liquid content), the adjustment of parameters (e.g. layering, coalescence and breakage rate) can provide a quantitative prediction of the granulation process

Rheological modeling of particle flows in high shear granulation

High shear granulation is an important process in a wide variety of applications, more specifically in pharmaceutical industries as a basic step in the tableting process. The process includes two major steps: dry high shear granulation and wet high shear granulation. It aims at producing granules with a specific size and material composition. The quality of the process is determined by the flow regime. Therefore, a better understanding of the flow regime is required. Computational simulation of such systems is traditionally performed by tracking each particle and resolving its binary collision and interaction with other particles. This approach is not feasible for industrial granulators with billions of particles. The aim of this study is to evaluate the possibility of applying various continuum modeling options in studying dense or multi-regime granular flows. Kinetic Theory of Granular Flow formulates the dilute parts of the system, whereas there is no strong agreement on any approach to modeling dense granular flows. In this study, a recent model proposed by Jop et al. is applied as an alternative to the model by Schaeffer, traditionally used for such flow regimes.The results show that the present model is not only simple, but also clearly predictive. Besides, considering the simplicity of the model compared to its alternatives (KTGF or DEM), adding more details to develop the model can be performed with fewer obstacles. In order to validate the model proposed in this study, model results are compared with experiments performed in a disc impeller granulator. The experimental results were analyzed using advanced techniques including a high speed camera and Particle Image Velocimetry (PIV). Keywords: high shear granulation, continuum modeling, rheology, disc impelle

Rheological modeling of particle flows in high shear granulation

High shear granulation is an important process in a wide variety of applications, more specifically in pharmaceutical industries as a basic step in the tableting process. The process includes two major steps: dry high shear granulation and wet high shear granulation. It aims at producing granules with a specific size and material composition. The quality of the process is determined by the flow regime. Therefore, a better understanding of the flow regime is required. Computational simulation of such systems is traditionally performed by tracking each particle and resolving its binary collision and interaction with other particles. This approach is not feasible for industrial granulators with billions of particles. The aim of this study is to evaluate the possibility of applying various continuum modeling options in studying dense or multi-regime granular flows. Kinetic Theory of Granular Flow formulates the dilute parts of the system, whereas there is no strong agreement on any approach to modeling dense granular flows. In this study, a recent model proposed by Jop et al. is applied as an alternative to the model by Schaeffer, traditionally used for such flow regimes.The results show that the present model is not only simple, but also clearly predictive. Besides, considering the simplicity of the model compared to its alternatives (KTGF or DEM), adding more details to develop the model can be performed with fewer obstacles. In order to validate the model proposed in this study, model results are compared with experiments performed in a disc impeller granulator. The experimental results were analyzed using advanced techniques including a high speed camera and Particle Image Velocimetry (PIV). Keywords: high shear granulation, continuum modeling, rheology, disc impelle

Rheological modeling of particle flows in high shear granulation

High shear granulation is an important process in a wide variety of applications, more specifically in pharmaceutical industries as a basic step in the tableting process. The process includes two major steps: dry high shear granulation and wet high shear granulation. It aims at producing granules with a specific size and material composition. The quality of the process is determined by the flow regime. Therefore, a better understanding of the flow regime is required. Computational simulation of such systems is traditionally performed by tracking each particle and resolving its binary collision and interaction with other particles. This approach is not feasible for industrial granulators with billions of particles. The aim of this study is to evaluate the possibility of applying various continuum modeling options in studying dense or multi-regime granular flows. Kinetic Theory of Granular Flow formulates the dilute parts of the system, whereas there is no strong agreement on any approach to modeling dense granular flows. In this study, a recent model proposed by Jop et al. is applied as an alternative to the model by Schaeffer, traditionally used for such flow regimes.The results show that the present model is not only simple, but also clearly predictive. Besides, considering the simplicity of the model compared to its alternatives (KTGF or DEM), adding more details to develop the model can be performed with fewer obstacles. In order to validate the model proposed in this study, model results are compared with experiments performed in a disc impeller granulator. The experimental results were analyzed using advanced techniques including a high speed camera and Particle Image Velocimetry (PIV). Keywords: high shear granulation, continuum modeling, rheology, disc impelle

Modeling dilute and dense granular flows in a high shear granulator

This study models a high shear granulation system, including both dense and dilute regions. The dense region is modeled using an approach in which the system is treated as a visco-plastic fluid and the rheology of such a fluid is evaluated. The dilute regions are modeled by the standard Kinetic Theory of Granular Flow (KTGF). The switching between the models is accounted for by using the dimensionless inertial number, defined as the ratio shear forces/pressure forces. The results compare favorably with experimental data for a disk impeller high shear granulator. Granular temperatures and volume fractions, in particular, are well captured by the aforementioned model. The velocity profiles show better agreement with experimental data as compared to previous studies. (C) 2014 Elsevier B.V. All rights reserved

Characterization of force networks in a dense high-shear system

We detect the strong force networks in a dense high shear system and we study their structure and stability in response to the variation of the shearing rate. The presence of strong force networks, which are usually of heterogeneous structure, restricts particle movements and can impose non-local mechanisms of momentum transfer. We identify such networks in a dense high shear system through the algorithm of community detection. Moreover, we explain the association between the mechanisms of momentum transfer and the structure, population, strength and stability of the force networks by tracking the spatial and temporal evolution of the detected networks. In addition, we show that the assumption of a monodispersed assembly of particles leads to an unrealistic enlargement of the force networks, underestimating both the rate of energy dissipation and the rate of mixing

Multiscale rheophysics of nearly jammed granular flows in a high shear system

We investigate non-local features of granular flows in nearly jammed configurations. We identify the presence of contact networks and crystallization as the reasons for such a behavior and perform Discrete Element Simulations on a high shear disk impeller granulator. The association of particle properties (e.g. the coefficients of restitution and friction) with the observed flow structures is studied using multivariate data analysis and multilinear optimization. The effect of polydispersity on the structure of the contact networks is studied. A singularity in the momentum flux is observed when approaching a monosized particle assembly, implying the onset of crystallization. Macroscopic quantities, such as the velocity profiles and momentum flux, are linked to microscopic data from DEM simulations through several statistical methods: the spectral analysis (giving dominant frequencies of the flow), coordination numbers that map the local flow regimes and the pair correlation function that is weakly associated with the variations of the flow structure. (C) 2017 Elsevier B.V. All rights reserved