摘要:

AbstractThe reliability of dynamic measurement methods ofklain fermentors using a step oxygen concentration change in the feed gas was tested. The tests were performed both for the original variant using the nitrogen ⇌ air exchange and the newly presented variant using the oxygen‐enriched air (27 vol % O2) → air exchange. The testing consisted in comparingklavalues determined from these methods with values determined from the steady‐state Na2SO3feeding method and the dynamic pressure method, the reliability of which was proven earlier. The measurements were done in water (coalescent batch) and in 0.5MNa2SO4solution with and without the addition of 1 wt % carboxymethylcellulose (noncoalescent batches). It was found that in noncoalescent liquids the methods tested give extremely lowklavalues (as low as 15% of the correct value). The methods are defective in principle irrespective of the gases used for e

ISSN:0006-3592    

DOI:10.1002/bit.260380402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractAirlift bioreactor operations have been studied for the growth‐associated production of secondary metabolites from plant cell suspension cultures. The model system used in this work wasThalictrum rugosumproducing berberine, an isoquinoline alkaloid. The airlift system was well suited for growth ofThalictrumcell suspension cultures unless the cell density was high. At high cell density, the airlift system with a draught tube was not adequate due to large aggregates clogging the recirculation paths. This was overcome by use of a cell scraper in the reactor. For berberine production, gas‐stripping also played a significant role and it was discovered that CO2and ethylene were important for product formation. By supplying a mixture of CO2and ethylene into the airlift system, the specific berberine content was increased twofold. It is evident that continuous gas sparging was harmful for the production of berberine without supplementation with other ga

ISSN:0006-3592    

DOI:10.1002/bit.260380403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractPronounced spatial nonuniformities in cell density, physiology, and activity frequently arise within densely packed immobilized cell supports. For a more fundamental understanding of immobilized cell phenomena, we have developed high‐resolution microfluorimetric procedures to analyze local variations in both immobilized cell loading and growth rate. Fluorescent staining of total cellular DNA provides a measure of local biomass density. Actively growing (DNA synthesizing) cells are marked by pulse‐labeling newly synthesized DNA with the thymine analog, bromouracil. An immunofluorescent technique allows subsequent detection of spatial variations in DNA synthesis rates. These procedures enable the influence of mass‐transfer limitations and other immobilization effects on cell distribution and activity to be readily quantified. We demonstrate this approach through analysis of the patterns of growth ofEscherichia colientrapped within Sr‐alginate gel beads. The experimental techniques are potentially applicable to a variety of other aggregate cell

ISSN:0006-3592    

DOI:10.1002/bit.260380404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractA Semimechanistic mathematical model is developed which describes the growth ofRhizopus oligosporusin a model solid‐state fermentation system. Equations are presented for the release of glucoamylase, the diffusion of glucoamylase, the hydrolysis of starch, the generation and diffusion of glucose, and the uptake of glucose and conversion into new biomass. Good agreement of the model with the experimental data was obtained only after the glucoamylase diffusivity and the maximum specific glucose uptake rate were altered from their originally determined values. The model recognizes the distributed nature of the solid‐state fermentation and therefore is able to predict the concentration profiles of the system components within the substrate. The model provides an insight into the possible rate‐limiting steps in solid‐state fermentation—the generation of glucose within the substrate and the resulting availability of glucose at th

ISSN:0006-3592    

DOI:10.1002/bit.260380405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe high‐pressure homogenization ofEscherichia coli, strain JM101, containing inclusion bodies of recombinant porcine somatotropin was investigated. A novel technique employing an analytical disc centrifuge was used to monitor the disruption. This a direct technique which measures cell disintegration rather than soluble protein release. The technique is particularly suited to measurements where the disruption approaches 100%. The disk centrifuge provides a size distribution of the homogenate, and furnishes evidence for the preferential disruption of larger cells. ForE. colicontaining inclusion bodies, and increase in the cell feed concentration from 145 g/L (wet weight) to 330 g/L resulted is poorer homogenization. Poorer disruption was also obtained by lowering the feed temperature from 20°C to 5°C. Only slight variations in performance were obtained by increasing the feed pH from 7.5 to 9.0 or by storing the feed at 4°C for 24 h prior to disruption. Comparison with uninducedE. colistrain JM101, showed that the disruption obtained is higher for bacteria containing a recombinant inclusion

ISSN:0006-3592    

DOI:10.1002/bit.260380406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractIn examining the growth kinetics of cell suspensions of opium poppy (Papaver somniferum), the increase in biomass with time was observed to be linear over the entire batch growth period of up to 20 days. Although batch growth profiles were reproducible utilizing the same inoculum, growth rates varied tremendously when experiments were inoculated with cells from different flasks. Both of these phenomena are difficult to explain with conventional batch growth models. In a series of a experiments, phosphate was determined to be the growth‐rate‐limiting substrate. By expressing growth rate in terms of the intracellular reserves of phosphorus, a growth model which expresses kinetics in terms of the intracellular phosphorus contents of the cells is shown to predict both linear growth character and inoculum dependent variability in growth. The stationary phase phosphate content of seven plant suspension cultures of different plant species was found to be comparable to phosphorus levels of phosphate‐starved poppy cells, which suggests that phosphate limitation may be common for plant tissue culture. The applicability of this model to other biological systems which display similar batch growth patterns when subjected to inorganic nutrient deprivation is disc

ISSN:0006-3592    

DOI:10.1002/bit.260380407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractA chemostat with population specific recycle was employed to alter the dynamics of a competitive mixed culture ofEscherichia coli. Based on differential expression of a functional maltoporin, the two populations were separated by specific adhesion on starch–Sepharose. The slower growing population was the recycled to the reactor. The specific recycle was successful in maintaining the slower growing population at a high level than in comparable reactors without recycl

ISSN:0006-3592    

DOI:10.1002/bit.260380408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe fractal nature microbial aggregates is a function of the type of microorganism and mixing conditions used to develop aggregates. We determined fractal dimensions from length‐projected area (D2) and length‐number scaling (D3) relationships. Aggregates ofZoogloea ramigeradeveloped in rotating test tubes were both surface and mass fractals, with fractal dimensions ofD2= 1.69 ± 0.11 andD3= 1.79 ± 0.28 (±standard deviation), respectively. When we grew this bacteria in a bench‐top fermentor, aggregates maintained their surface fractal characteristics (D2= 1.78 ± 0.11) but lost their mass fractal characteristics (D3= 2.99 ± 0.36). Yeast aggregates (Saccharomyces cerevisae) grown in rotating tests tubes had higher average fractal dimensions than bacterial aggregates grown under physically identical conditions, and were also considered fractal (D2= 1.92 ± 0.08 andD3= 2.66 ± 0.34). Aggregates porosity can be expressed in term of a fractal dimensions, but average porosities are higher than expected. The porosities of yeast aggregates (0.9250–0.9966) were similar to porosities of bacterial aggregates (0.9250‐0.9966) cultured under the same physical conditions, although bacterial aggregates developed in the reactor had higher average porosities (0.9857‐0.9980). These results suggest that that scaling relationships based on fractal geometry may be more useful than equations derived from Euclidean geometry for quantifying the effects of different fluid mechanical environments on aggregates morphology and characteristics such as density, porosity, and proj

ISSN:0006-3592    

DOI:10.1002/bit.260380409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractEarlier experiments in our lab investigated the metabolic limitations of cloned‐gene expression in bacterial cells (for over‐production of β‐lactamase). These experiments showed that the steady‐state concentration of ribosomal RNA decreased upon plasmid amplification while both the synthesis rate and steady‐state β‐lactamase mRNA level increased significantly. This appeared to indicate substantial limitation exist within the transnational machinery of the bacterial cell at high copy numbers. To establish the generality of this phenomenon, the impact increasing protein expression from pa plasmid by chemically inducing a strong promoter while maintaining constant copy number has been investigated. A plasmid has been constructed which contains thelacZgene under control of thetacpromoter and contains theparBstability locus to maintain plasmid stability. Using this vector, β‐galactosidase expression in chemostat cultures operated at specific growth rates of 0.6 h−1was induced with IPTG such that enzyme activity was varied over a 460‐fold range. When fully induced β‐galactosidase protein production represented 14 wt % of total cell protein. As transcription was induced, the synthesis rate of the β‐galactosidase mRNA increased 42‐fold while the steady‐state level of β‐galactosidase mRNA increased only fourfold. This indicates stability may play a larger role for β‐galactosidase expression with a strong promoter than seen with β‐lactamase production in the elevated copy number system. Furthermore, rRNA synthesis rates increased at high expression rates as seen in the copy number experiments. However, unlike the amplified‐plasmid system, the steady‐state levels of rRNA increased as well. Since the total protein levels closely followed the steady‐state level of eRNA, transnational limitations are again suggested fo

ISSN:0006-3592    

DOI:10.1002/bit.260380410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractAn industrial‐scale methods for harvest of biologically active proteins form mammalian cell culture has been developed using tangential flow filtration. A robust and economical process capable of processing approximately 5000 L conditioned media/h with protein yields in excess of 99% has been achieved. A completely contained system has been designed in which total cell number and viability are maintained throughout the process. The process has successfully been implemented at 1.25 × 104L scale for the recovery of kilogram quantities of pharmaceutical proteins such as recombinant tissue type plasminogen activator (rt

ISSN:0006-3592    

DOI:10.1002/bit.260380411

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY