摘要:

AbstractThe problem of dynamically modeling a chemostat is addressed. Using the results of continuous culture experiments for the growth of a strain ofSaccharomyces cerevisiaeon a glucose‐limited medium, a general approach to developing dynamic models is discussed. The approach to develop and verify the model involves three different types of experiments: steady‐state, dynamic step response, and feedback identificat

ISSN:0006-3592    

DOI:10.1002/bit.260360502

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe adsorption of cellulase on cellulose and a lignacious residue was examined by using cellulase fromTrichoderma reesei, hardwood pretreated by dilute sulfuric acid under high pressure, and a lignacious residue prepared by a complete enzymatic hydrolysis of the pretreated wood. A significant amount of cellulase was found to adsorb on the lignacious residue during the hydrolysis of the pretreated wood. Hence, the adsorption of enzyme on the lignacious residue as well as cellulose must be taken into account in the development of the hydrolysis kinetics. It was found that the adsorption of enzyme on cellulose and on the lignacious residue could be represented by Langmuir type isotherms. The data show that the pretreatment at a higher temperature results in more enzyme adsorption on the cellulose fraction and less on the lignacious residue fraction. The relationship between the hydrolysis rate and the amount of enzyme adsorbed is discussed.

ISSN:0006-3592    

DOI:10.1002/bit.260360503

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

年代:1990

数据来源: WILEY

摘要:

AbstractSpontaneous oscillations occur in glucose‐limited continuous cultures ofSaccharomyces cerevisiaeunder aerobic conditions. The oscillatory behavior is detectable as a periodic change of many bioparameters such as dissolved oxygen, ethanol production, biomass concentration, as well as cellular content of storage carbohydrates and is associated to a marked synchronization of the yeast population. These oscillations may be related to a periodic accumulation of ethanol produced by yeast in the culture medium.The addition of ethanol to oscillating yeast cultures supports this hypothesis: indeed, no effect was observed if ethanol was added when already present in the medium, while a marked phase oscillation shift was obtained when ethanol was added at any other time. Moreover, the addition of ethanol to a nonoscillating culture triggers new oscillations. An accurate analysis performed at the level of nonoscillating yeast populations perturbed by addition of ethanol showed that both the growth rate and the protein content required for cell division increased in the presence of mixed substrate (i.e., ethanol plus limiting glucose). A marked synchronization of the yeast population occurred when the added ethanol was exhausted and the culture resumed growth only on limiting glucose. A decrease of protein content required for cell division was also apparent. These experimental findings support a new model for spontaneous oscillations in yeast cultures in which the alternative growth on limiting glucose and limiting glucose plus ethanol modifies the critical protein content required for cell divisio

ISSN:0006-3592    

DOI:10.1002/bit.260360504

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

年代:1990

数据来源: WILEY

摘要:

AbstractPlant cell cultures ofLithospermum erythrorhizonwere carried out to produce shikonin by in situ extraction and cell immobilization in calcium alginate bead in shake flask cultures. In situ product extraction and cell immobilization enhanced shikonin production and facilitated product recovery. In situ extraction byn‐hexadecane and cell immobilization by calcium alginate gave higher specific shikonin productivities of 7.4 and 2.5 times, respectively, than those from the cultures of free cells without extraction. Simultaneous use of both techniques increased specific and volumetric productivities of shikonin 25‐ and 15‐fold, respectively. In calcium alginate immobilized cell cultures,n‐hexadecane addition at an early stage (before 15 days) was effective for shikonin production, and solvent addition after 15 days of the culture significantly reduced shikonin production. Higher numbers of plant cell immobilized bead inoculation did not increase shikonin production and sucrose consumption. Most of the produced shikonin was dissolved in the solven

ISSN:0006-3592    

DOI:10.1002/bit.260360505

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

年代:1990

数据来源: WILEY

摘要:

Abstractβ‐Galactosidase served as a model system to explore the feasibility of enhancing the selectivity of a low‐cost, easily scaled separation method—precipitation. Enhanced selectivity was sought by fusing the enzyme with polypeptide tails including 5 and 11 aspartaies. The unfused protein could not be selectively removed from theEscherichia colicell extract by precipitation with polyethylenimine (PEI), but the longest fusion could be selectively removed. The presence of nucleic acids limited the purification attainable. Pretreatment with nuclease followed by diafiltration resulted in an extract from which the same fusion could be precipitated with greater than fivefold enrichment, while the untailed enzyme remained unenriched by the same precipitation step. Selectivitiy is attributed to the binding strength of the polyanionic tails to the polycation

ISSN:0006-3592    

DOI:10.1002/bit.260360506

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

年代:1990

数据来源: WILEY

摘要:

AbstractWe show that when freely suspended hybridoma cells are cultured in an agitated bioreactor, two fluid‐mechanical mechanisms can cause cell damage and growth retardation. The first is present only when there is a gas phase, and is associated with vortex formation accompanied by bubble entrainment and breakup. In the absence of a vortex and bubble entrainment, cells can be damaged only at very high agitation rates, above approximately 700 rpm, by stresses in the bulk turbulent liquid. Cell damage then correlates with Kolmogorov eddy sizes similar to or smaller than the cell size. In the absence of a vortex, the entrainment and motion of very fine bubbles cause no growth retardation even at agitation rates as high as 600 rp

ISSN:0006-3592    

DOI:10.1002/bit.260360507

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe separation of host and recombinantEscherichia colibacterial cells has been studied using the surface‐sensitive technique of partitioning in aqueous two‐phase polymer systems. Experiments were designed to probe charge‐and hydrophobicity‐related property differences of antibiotic‐resistant recombinant cells and their antibiotic‐sensitive hosts. Differential partitioning was observed in both charge‐sensitive and non‐charge‐sensitive phase systems for three host–recombinant cell systems, but the non‐charge‐related effects appear to have a greater impact on partitioning behavior. This result suggests that plasmid‐encoded products related to antibiotic resistance modify the surface hydrophobicity of theE. colibacterial cell and that these differences can be expl

ISSN:0006-3592    

DOI:10.1002/bit.260360508

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

年代:1990

数据来源: WILEY

摘要:

AbstractAs part of the process optimization of a two‐stage continuous culture system, the effect of growth rate μ 2appon the performance of the second stage (production stage) was studied in a recombinantEscherichia coliK12 (ΔH1Δtrp/pPLc23trpA1). Important parameters considered were specific gene expression rate, plasmid content, and plasmid stability, all of which were closely related to the cell growth rate and the production rate of the cloned gene product (trpα). When operating conditions were maintained constant (T1= 35°C,D1= 0.9 h−1,T2= 40°C, andD2= 0.7 h−1) and μ 2appwas varied, plasmid content in the second stage showed its maximum at μ 2app= 0.4 h−1and decreased thereafter. Specific gene expression rate linearly increased with increasing μ 2app, while plasmid stability decreased. Optimum cell growth rate giving the maximum value in overall productivity was observed at around μ 2app= 0.4 h−1. The contribution or role of the three parameters, specific gene expression rate, plasmid content, and plasmid stability in exhibiting the maximum productivity at t

ISSN:0006-3592    

DOI:10.1002/bit.260360509

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

年代:1990

数据来源: WILEY

摘要:

AbstractA novel protein purification process using affinity‐ligand‐modified liposomes and membrane ultrafiltration is described. The feasibility of the process was tested using trypsin as the model protein andp‐aminobenzamidine (PAB) as the affinity ligand for trypsin. The affinity liposomes were prepared by covalently attaching PAB to the surface of small unilamellar liposomes via the hydrophilic spacer arm diglycolic acid. The liposomes were comprised of dimyristoyl phosphatidyl choline, cholesterol, and dimyristoyl phosphatidyl ethanolamine to which the diglycolic acid was attached. The equilibrium binding constant between trypsin and immobilized PAB was shown to be dependent on the PAB density of the liposome surface. Bound trypsin was eluted from the liposomes by the trypsin inhibitor benzamidine. Trypsin was purified from a trypsin/chymotrypsin mixture and from one of its naturally occurring sources, porcine pancreatic extract. A recovery yield from the crude mixture of 68% was obtained with a trypsin purity of 98%. The affinity‐modified liposomes were stable in the complex mixture and retained their trypsin binding capacity after multiple adsorption/elution cycles over a 30‐d

ISSN:0006-3592    

DOI:10.1002/bit.260360510

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

年代:1990

数据来源: WILEY

摘要:

AbstractMathematical formulation was made for the performance evaluation of extractive fermentation using multiple solvents. Two types of solvent‐supplying strategies were considered. One is to add multiple solvents simultaneously and the product is removed at one time. Another is to add them one by one consecutively. Computer simulation was made for batch, fed‐batch, and repeated fed‐batch operation of acetone–butanol fermentation to show the power of the approach. The result shows that the significant performance improvement in terms of the productivity and the product concentration is expected when two extractants such as oleyl alcohol and benzyl benzoate are used as compared with the case of using only one

ISSN:0006-3592    

DOI:10.1002/bit.260360511

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

年代:1990

数据来源: WILEY