Bioreactors biomass concentration

A steady state is when the conditions in the bioreactor (biomass concentration, residual substrate concentration etc) remain constant over time. 

Dilution rate 0.4 h"1 gives highest productivity, but 25% of the substrate remains unused. Dilution rate 0.3 h"Y gives better substrate utilisation but with reduced productivity. Both these dilution rates require minimum OTRs greater than the bioreactor can supply. This means that such biomass concentrations could not be produced in practice. 

It is assumed that both state variables x, and x2 are measured with respect to time and that the standard experimental error (oe) is 0.1 (g/L) for both variables. The independent variables that determine a particular experiment are (i) the inoculation density (initial biomass concentration in the bioreactor), Xq i, with range 1 to 10 g/L, (ii) the dilution factor, D, with range 0.05 to 0.20 h 1 and (iii) the substrate concentration in the feed, cF, with range 5 to 35 g/L. 

Decolorization of azo dye R016 by immobilized cultures of I. lacteus was compared in three different reactor systems [59]. Different size of PuF was used for immobilization in reactors. Biomass concentration was reported to be 11.6, 8.3, and 4.9 g dw/L in Small Trickle Bed Reactor (STBR), Large Trickle Bed Reactor, and Rotating Disk Bioreactor, respectively. Decolorization rate was found high in STBR, where 90% decolorization rates were achieved after 3 days. Dye decolorization was highly efficient, but no direct relationship between the extracellular enzyme activities (laccase and MnP) and dye decolorization capacity was found. 

Zabriski and colleagues 145, 46] first used culture fluorescence as an on-line estimate of viable biomass during the batch cultivation of Saccharomyces cere-visiae, a species of Streptomyces, and a species of Thermoactinomyces. They simply linearized the fluorescence to biomass data in order to find a direct function between NADH-dependent culture fluorescence and biomass concentration in the bioreactor. In the following years several other authors reported - on the basis of these results - on the estimation of biomass concentration from culture fluorescence data as shown in Table 1. 

The choice of the bioreactor type for denitrification of NO to N2 and the regeneration of the chelating agent Fe(II)EDTA2 is another important decision. A properly designed and controlled bioreactor should ensure high biomass concentration, constant temperature and pH, optimal mixing and correct shear conditions. Other important aspects are listed below ... 

Geppert and Thielemann [125] and Geppert et al. [126] have used a similar method but a different instrument to measure a suspension aliquot outside the bioreactor and reported a fairly good linear correlation between OD and biomass concentration for some bacteria and yeasts. 

Electronic noses provide new possibilities for monitor the state of a cultivation non-in-vasively in real-time. The electronic nose uses an array of chemical gas sensors that monitors the off-gas from the bioreactor. By taking advantage of the off-gas components different affinities towards the sensors in the array it is possible with the help of pattern recognition methods to extract valuable information from the culture in a way similar to the human nose. For example, with artificial neural networks, metabolite and biomass concentration can be predicted, the fermentability of a medium before starting the fermentation estimated, and the growth and production stages of the culture visualized. In this review these and other recent results with electronic noses from monitoring microbial and cell cultures in bioreactors are described. 

The objective of the experiments carried out in this pilot plant was to determine the optimal values of some operational parameters, such as biomass concentration, transmembrane pressure, flow rate, and hydrauhc retention time, the last defined as the relationship between the volume of the bioreactor and the daily flow discharge of permeate. The working plan was as follows ... 

Theoretical considerations show that, with a methanol concentration of 701 m in the incoming medium to ffie bioreactor, the biomass concentration and residual methanol concentration (in outgoing medium) would vary with dilution rate as outlined below. 

On the basis of a new method correlating the biomass concentration with the vertical pressure gradient of the fluidized bed, a comprehensive optimization and modeling procedure has been elaborated for fluidized bed bioreactors. 

Another special type of membrane bioreactor, a biomass concentrator reactor (BCR) [42,56] uses gravity to filtrate the suspension containing bacterial mass and groundwater. 

Lactic acid is an important additive and preservative agent in the chemical, cosmetics, pharmaceutical, and food industries. It is also used as the base for the production of biodegradable polymers like polylactates [4.12]. Its current worldwide production is estimated to be 40,000 tons per year. The results reported by Olmos-Dichara and coworkers [4.13] are typical of the results reported in many of the prior studies of this reaction system. They carried out a study comparing the performance of a batch reactor and a MBR for the production of lactic acid using L. cassei sp. rhamnosus as a biocatalyst. The MBR consists of the batch bioreactor coupled with a cross-flow mineral membrane filtration unit. MBR productivity was eight times that of the batch reactor, while the biomass concentration (77g f ) in the MBR was 19 times that found in the batch culture. 

In many bioreactor models intraparticle concentration gradients are ignored, and growth is modeled as depending only on the biomass concentration and temperature. In this case overall consmnption of oxygen, production of CO2, or consumption of nutrients can be calculated assuming that both growth-related and maintenance metabolism are involved ... 

As we saw in Section 8.3.2, one can develop equations describing the performance of an arbitrary CSTR in a cascade of CSTRs. We can also develop the corresponding equations for the nth bioreactor in an extended cascade of stirred tanks by conducting an analysis on the nth bioreactor. The feed stream exiting bioreactor n - 1 and entering reactor n has a volumetric flow rate V, a concentration of the hmiting substrate equal to s , and a biomass concentration. This stream enters well-stirred reactor n, which... 

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