Software sensors for biomass concentration estimation in filamentous microorganism cultivation process

In this study, the potential of two software sensors for on-line estimation of biomass concentration during cultivation of filamentous microorganisms is examined. The first sensor is based on common bioreactor off-gas analyses, and uses the assumption of the biomass concentration linear dependence on the square root of cumulative O-2, consumption. Parameters of the semi-empirical data-driven software sensor based on off-gas analysis were calculated from experimental cultivation data using linear regression. The second sensor is based on biocalorimetry, i.e., the on-line calculation of metabolic heat flux from general enthalpy balance of the bioreactor. The software sensor based on biocalorimetry thus essentially represents a model-driven approach, making use of a fundamental process model based on the enthalpy balance around the bioreactor. This approach has been combined with the experimental identification of the specific biomass heat production, which represents the main process-specific parameter of the software sensor based on biocalorimetry. For this sensor, the accuracy requirements on the process variable on-line measurements were also analysed. The experimental data from the pilot-scale antibiotics Nystatin production by a bacterium Streptomyces noursei were used to calculate the specific bioprocess heat production value using linear regression. The achieved results enabled us to propose a new on-line indicator calculated as the ratio of the outputs of both sensors, which can serve as a timely warning of the risk of undesired nutritional conditions of a culture characterized as underfeeding.Technology Agency of the Czech Republic [TA03010165

Gas-liquid mass transfer rates in unbaffled tanks stirred by PBT: scale-up effects and pumping direction

Unbaffled stirred tanks are increasingly recognized as a viable alternative to common baffled tanks for a range of applications such as biochemical, food or pharmaceutical processes where the presence of baffles is undesirable for some reason. In this work, the mass transfer performance of unbaffled stirred tanks with pitched blade turbine, operating either in up-pumping or down-pumping mode, was investigated. The influence of impeller size and liquid viscosity were also investigated. The mass transfer intensity was measured by means of the Simplified Dynamic Pressure. Method: The measurements concerned both coalescent and non-coalescent (viscous) batches. Results: confirm that increasing apparatus size has a slightly positive effect on gas-liquid mass transfer coefficient. It was also found that when the PBT is operating in the up-pumping mode the formation of surface oscillations, which lead to undesired instabilities of the whole apparatus, is conveniently minimized. In the super-critical regime, the unbaffled tanks provide a performance comparable with that of the standard (baffled) bioreactors at the same power dissipation, which makes them a viable alternative for general fermentation operations and other gas–liquid reactions

Scale-up and viscosity effects on gas-liquid mass transfer rates in unbaffled stirred tanks

The interest in the process industry on unbaffled stirred tanks has greatly expanded in the last years because they may bring about significant advantages in a number of applications, including biochemical, food and pharmaceutical processes where the presence of baffles is undesirable for several reasons. Despite their application potential, unbaffled vessels still lack fundamental information, due to the fact that only recently their capabilities have started being dug out. The lack of information on scale up effects is possibly the main reason hindering practical applications. In this work the influence of vessel size and liquid viscosity on the mass transfer performance in unbaffled stirred vessels, is investigated. As regards the first issue (scale-up) quite surprisingly results show that comparable mass transfer coefficients may be obtained in larger vessels, for a given power input per unit volume, with typical kLa values up to 2 Ã 10â3sâ1in ungassed conditions and of 2 Ã 10â2sâ1in gassed conditions. This is opposite to expectations based on the fact that the exchange surface in subcritical conditions only grows with D2while volume grows with D3. Notably, the same result is obtained at an increased liquid viscosity (a feature often exhibited by biological cultivation broths) and confirms that unbaffled stirred tanks should be regarded as a strong candidate for industrial applications. Finally, also at the larger scale, in the super-critical regime unbaffled tanks are found to provide a performance comparable with that of standard (baffled & sparged) stirred tanks, hence resulting in a viable alternative to baffled tanks for all gasâliquid processes and bio-processes

Radiační angiosarkom prsu: Mezinárodní multicentrická analýza

Radiation-associated angiosarcoma (RAAS) is a rare and serious complication of breast irradiation. Due to the rarity of the condition, clinical experience is limited and publications on this topic include only retrospective studies or case reports.Výsledky překladu Radiační angiosarkom (RAAS) je vzácnou a závažnou komplikací ozáření prsu. Vzhledem k vzácnosti stavu jsou klinické zkušenosti omezené a publikace na toto téma zahrnují pouze retrospektivní studie nebo kazuistiky