Calorimetry and thermodynamic aspects of heterotrophic, mixotrophic, and phototrophic growth

A simple stoichiometric model is proposed linking the biomass yield to the enthalpy and Gibbs energy changes in chemo-heterotrophic, mixotrophic, and photo-autotrophic microbial growth. A comparison with calorimetric experiments on the algae Chlorella vulgaris and Chlorella sorokiniana confirmed the trends but revealed large calorimetric measurement inaccuracies. The calorimetric data on purely photo-autotrophic growth was, however, in fair agreement with calculations. The thermodynamic characteristics of photosynthetic growth, including an estimation of the Gibbs energy dissipation, are compared with similar data for chemotrophic microbe

CHO immobilization in alginate/poly- l -lysine microcapsules: an understanding of potential and limitations

Microencapsulation offers a unique potential for high cell density, high productivity mammalian cell cultures. However, for successful exploitation there is the need for microcapsules of defined size, properties and mechanical stability. Four types of alginate/poly-l-Lysine microcapsules, containing recombinant CHO cells, have been investigated: (a) 800μm liquid core microcapsules, (b) 500μm liquid core microcapsules, (c) 880μm liquid core microcapsules with a double PLL membrane and (d) 740μm semi-liquid core microcapsules. With encapsulated cells a reduced growth rate was observed, however this was accompanied by a 2-3 fold higher specific production rate of the recombinant protein. Interestingly, the maximal intracapsular cell concentration was only 8.7×107cell mL-1, corresponding to a colonization of 20% of the microcapsule volume. The low level of colonization is unlikely to be due to diffusional limitations since reduction of microcapsule size had no effect. Measurement of cell leaching and mechanical properties showed that liquid core microcapsules are not suitable for continuous long-term cultures (>1month). By contrast semi-liquid core microcapsules were stable over long periods with a constant level of cell colonization (ϕ=3%). This indicates that the alginate in the core plays a predominant role in determining the level of microcapsule colonization. This was confirmed by experiments showing reduced growth rates of batch suspension cultures of CHO cells in medium containing dissolved alginate. Removal of this alginate would therefore be expected to increase microcapsule colonizatio

The Use of Virtual Calibrations to Facilitate Understanding of Factor Analysis

Tutorial published on: http://www.chemometrics.se/File/VirtualCalibrations.pd

Cole-Cole, linear and multivariate modeling of capacitance data for on-line monitoring of biomass

This work evaluates three techniques of calibrating capacitance (dielectric) spectrometers used for on-line monitoring of biomass: modeling of cell properties using the theoretical Cole-Cole equation, linear regression of dual-frequency capacitance measurements on biomass concentration, and multivariate (PLS) modeling of scanning dielectric spectra. The performance and robustness of each technique is assessed during a sequence of validation batches in two experimental settings of differing signal noise. In more noisy conditions, the Cole-Cole model had significantly higher biomass concentration prediction errors than the linear and multivariate models. The PLS model was the most robust in handling signal noise. In less noisy conditions, the three models performed similarly. Estimates of the mean cell size were done additionally using the Cole-Cole and PLS models, the latter technique giving more satisfactory result

Biotechnology in Lausanne: The Rh D Project

Hemolytic disease of the newborn is an often fatal condition of some newborn babies due to the immunogenicity of their Rh D positive erythrocytes in the Rh D negative mother. This condition can be prevented by injecting anti-Rh D antibodies. The current source of these antibodies is blood from immunized human donors. In order to avoid problems with limited supply and donor safety, the Rh D project was set up to develop recombinant monoclonal anti-Rh D antibodies as a possible replacement. In a multidisciplinary collaboration between the Zentrallaboratorium Blutspendedienst (ZlB) of the Swiss Red Cross, the Center of Biotechnology of the University and the EPFL (CBUE), and the Institute of Chemical and Biochemical Engineering (EPFl), co-funded by the Swiss National Science Foundation and ZLB, a candidate monoclonal anti-Rh D antibody has been selected, expressed in CHO cells, and a manufacturing process for large-scale production has been developed

A calorimetric investigation of the aerobic cultivation of Kluyveromyces fragilis on various substrates

A novel heat-flux calorimeter was used to study the aerobic batch growth of the facultative yeast K. fragilis on glucose [50-99-7], galactose [59-23-4], lactose [63-42-3], and deproteinized whey permeate. The calorimetric data enabled optimization of the defined medium compn. with respect to vitamin and trace element requirements. Direct relationship between heat evolved and biomass concn., O2 consumption rate, and CO2 evolution rate were obsd. with values for YQ/X, YQ/O, and YQ/C of 9.43, 440, and 474 kJ/mol, resp., for growth on whey permeate. The value for YQ/X varied as a function of substrate with a value of 9.43-10.59 kJ/g during growth on lactose compared with 12.66-12.82 kJ/g for growth on glucose and galactose. Energy and C balances agreed to within a few percent, esp. when alc. prodn. and stripping into the gas phase was taken into account. Using combined energy and C balances, the extent of product (EtOH [64-17-5]) formation could be estd. based on the measured biomass (YX/S) and heat yield (YQ/X). Using measured heat yields in conjunction with further exptl. detd. yields, such as the CO2 yield, makes it possible to improve the ests. of all yield coeffs. Heat measurements may constitute a valuable tool for online detns. of the concn. of biomass, O2 uptake, CO2 evolution, and product formation in a fermn. system, thereby suggesting a future for calorimetry in process design and control. [on SciFinder (R)

A possible alternative mechanism for the oxidation of formaldehyde to formate

A survey of the occurrence of a no. of enzymes possibly involved in the C1 dissimilatory pathway in organisms using the serine pathway of C assimilation indicated that neither the methanol dehydrogenase nor the NH4-independent dye-linked formaldehyde dehydrogenase had a specific role in the oxidn. of formaldehyde. Conversely, the activities of enzymes involved in the methenyl-THF pathway were induced during growth on MeOH or MeNH2, suggesting a potential dissimilatory role for this pathway. [on SciFinder (R)

Fermentation control and the use of calorimetry

A novel heat-flux calorimeter was used to study the growth of Kluyveromyces fragilis on a variety of C substrates. Heat liberated was directly related to biomass formed and also to O2 consumed. Heat yield coeffs. derived from these relationships allowed the development of stoichiometries describing yeast growth. Since the sensitivity and speed of response of the calorimeter are higher than those of many other monitoring systems, such a system could be advantageously used to control fermns. [on SciFinder (R)

The use of calorimetry in biotechnology

A review with 98 refs. of the principles and technol. of biol. calorimetry, the factors affecting heat formation in microbial cultures, and the information concerning fermns. that may be gained by calorimetry