摘要:

AbstractIn this work the effects of environmental parameters on the performance of solid substrate fermentation (SSF) for protein production are studied. These parameters are (i) air flow rate, (ii) inlet air relative humidity, (iii) inlet air temperature, and (iv) the heat transfer coefficient between the outer wall of the fermentor and the air in the incubator. The air flow is supplied to effect cooling of the fermented mass by evaporation of water. A dynamic model is developed, which permits estimation of biomass content, total dry matter, moisture content, and temperature of the fermented matter. The model includes the effects of temperature and moisture content on both the maximum specific growth rate and the maximum attainable biomass content. The results of the simulation are compared with actual experimental data and show good agreement with them. The most important conclusions are that (i) the evaporative cooling of the biomass is very effective for temperature control and (ii) the air flow rate and the heat transfer coefficient have strong effects but they affect the biomass morphology and are not controllable easily. Also, a simple technique for the determination of the optimum temperature and moisture content profile for cell protein production is applied. The simulated biomass production increases considerably employing the optimum temperature and moisture content profiles. The ultimate goal is to implement the determined effects of the environmental parameters on the SSF biomass production and the temperature and moisture variation profiles to effectively control the SSF and optimize the biomass production. © 1993 John Wiley&Sons, Inc

ISSN:0006-3592    

DOI:10.1002/bit.260420202

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

年代:1993

数据来源: WILEY

摘要:

AbstractA mathematical model for anaerobic degradation of complex organic material, such as manure, has been developed. The model includes an enzymatic hydrolytic step and four bacterial steps and involves 12 chemical compounds. The model focuses on ammonia inhibition and includes a detailed description of pH and temperature characteristics in order to accurately simulate free ammonia concentration. Free ammonia and acetate constitute the primary modulating factors in the model. The model has been applied for the simulation of digestion of cattle manure in continuously stirred tank reactors (CSTRs), and results compare favorably with experimental data. © 1993 John Wiley&Sons, Inc

ISSN:0006-3592    

DOI:10.1002/bit.260420203

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe adhesion forces between various surfaces were measured using the “surface forces apparatus” technique. This technique allows for the thickness of surface layers and the adhesion force between them to be directly measured in controlled vapor or liquid environments. Three types of biological surfaces were prepared by depositing various lipid‐protein monolayers (with thicknesses ranging from 1 to 4 nm) on the inert, molecularly smooth mica surface: (i) hydrophobic lipid monolayers; (ii) amphiphilic polyelectrolyte surfaces of adsorbed polylysine; and (iii) deposited bacterial S‐layer proteins. The adhesion, swelling, and wetting properties of these surfaces was measured as a function of relative humidity and time. Initial adhesion is due mainly to the van der Waals forces arising from nonpolar (hydrophobic) contacts. Following adhesive contact, significant molecular rearrangements can occur which alter their hydrophobic–hydrophilic balance and increase their adhesion with time. Increased adhesion is generally enhanced by (i) increased relative humidity (or degree of hydration); (ii) increased contact time; and (iii) increased rates of separation. The results are likely to be applicable to the adhesion of many other biosurfaces, and show that the hydrophobicity of a lipid or protein surface is not an intrinsic property of that surface but depends on its environment (e.g., on whether it is in aqueous solution or exposed to the atmosphere), and on the relative humidity of the atmosphere. It also depends on whether the surface is in adhesive contact with another surface and—when considering dynamic (nonequilibrium) conditions—on the time and previous history of its interaction with that surface. © 1993 John W

ISSN:0006-3592    

DOI:10.1002/bit.260420204

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe strong interaction of hexa‐histidine fusion proteins with metal chelate adsorbents was utilized to immobilize β‐galactosidase with a hexa‐histidine peptide at the N‐terminus to the Ni2+‐nitrilotriacetic acid adsorbent. The fusion protein was cloned and expressed inEscherichia coli. The purified soluble fusion protein showed the same specific activity as the purified β‐galactosidase and retained 64 percent of its β‐galactosidase activity when bound to the adsorbent. To demonstrate the potential of the immobilized β‐galactosidase in organic chemistry, allyl‐β‐D‐galactosidase was synthesized from lactose and allyl alcohol on a gram scale. The same enzyme preparation was reused in three subsequent batches to prepare the model compound with high yield.

ISSN:0006-3592    

DOI:10.1002/bit.260420205

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe steady‐state metabolic parameters for a hybridoma cell line have been determined in continuous suspension–perfusion culture over a wide range of perfusion rates and cell bleed rates. Significant increases in viable cell concentrations and volumetric productivities were achieved at high perfusion rates and low cell bleed rates. At the low growth rates examined in this study, cellular metabolism shifted to become more oxidative, and as a result, the fraction of consumed substrate converted to inhibitory metabolic by‐products was reduced. Specific antibody productivity was found to be non–growth associated. © 1993 John Wiley&S

ISSN:0006-3592    

DOI:10.1002/bit.260420206

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

年代:1993

数据来源: WILEY

摘要:

AbstractLipase fromCandida cylindracea(CCL) was incorporated into polymerizable positively charged dialkylammonium bromide surfactant vesicles. The enzyme was incorporated by the use of the dehydration–rehydration method or by incubation. In the latter case, trapping efficiencies of up to 100% could be obtained. Activities of free and vesicle‐incorporated CCL were tested for three triglycerides: triacetin, tributyrin, and tricaprylin. Enzyme activity was lowest in homogeneous mixtures (triacetin and small concentrations of tributyrin) and highest in heterogeneous mixtures (tricaprylin and high concentrations of tributyrin). Entrapment in vesicular systems is advantageous, especially in homogeneous reaction mixtures and in the case of the production of insoluble fatty acid (caproate), because inhibition by the acid can be suppressed. The influence of several surface‐active additives, including vesicles, on the activity of lipase in triglyceride assays was tested. Vesicles have a positive influence on the activity, whereas other positively charged additives act as inhibitors. In the case of tricaprylin assays, the positively charged additives increase the activity. Finally, tryptic digestion for free and incorporated CCL were compared. Free CCL is readily inactivated, whereas incorporated enzyme is protected from proteolytic degradation. © 1993 John Wiley&Son

ISSN:0006-3592    

DOI:10.1002/bit.260420207

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

年代:1993

数据来源: WILEY

摘要:

AbstractSPA::EcoRI fusion protein was produced byEscherichia coliJM103 carrying the multicopy expression plasmid pMTC48, the multicopy repressor plasmid pRK248, and the multicopy protection plasmid pEcoR4 in a 60‐L working volume airlift tower loop reactor on M9 minimal medium with glucose. Cell mass concentration, total cell count, number of colony‐forming units, specific growth rate, yield coefficient, and metabolite (acetate, pyruvate, succinate, lactate, ethanol) concentrations were monitored during the growth phase and gene expression. Gene expression was induced by temperature shift or chemically by isopropyl‐thiogalactosidase in the airlift tower loop reactor (ALTR) at constant cultivation time and in a small stirred tank reactor at different cultivation times. During induction, the cultivation medium was supplemented with concentrated Luria–Bertani (LB) medium. The intracellular enzyme activity was evaluated as a function of the time after the start of the induction. It was found that the reduction of the glucose concentration and increase of the dissolved oxygen concentration reduced the acetate produced and increased the intracellular enzyme activity. © 1993 John Wiley&S

ISSN:0006-3592    

DOI:10.1002/bit.260420208

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

年代:1993

数据来源: WILEY

摘要:

AbstractAn experimental system has been constructed which enables on‐line measurements of phosphorus‐31 (31P) nuclear magnetic resonance (NMR) spectra for growing bacterial suspensions under anaerobic or aerobic conditions. A sample stream from a laboratory bioreactor is circulated to the NMR sample chamber in a gas exchange system which permits maintenance of aerobic conditions for high‐cell‐density cultures.31P NMR spectra with resolution comparable with those obtained traditionally using dense, concentrated, nongrowing cell suspensions can be obtained at cell densities above 25 g/L with acquisition times ranging from 14 to 3 minutes which decline as cell density increases. This system has been employed to characterize the changes in intracellular state of a stationary phase culture which is subjected to a transition from aerobic to anaerobic conditions. Both intracellular NTP level and cytoplasmic pH are substantially lower under anaerobic conditions. Also, the system has been employed to observe the response of a growing culture to external addition of acetate. Cells are able to maintain pH difference across the cytoplasmic membrane at extracellular acetate concentrations of 5 and 10 g/L. However, acetate concentrations of 20 g/L cause collapse of the transmembrane ΔpH and sharp reduction of the growth rate of the culture. The experimental configuration described should also permit NMR observations of many other types of microbial cultures and of other nuclei. © 1993 John Wiley&

ISSN:0006-3592    

DOI:10.1002/bit.260420209

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

年代:1993

数据来源: WILEY

摘要:

AbstractMany microbial and cell cultures exhibit phenomena that can best be described using a segregated modeling approach. Heterogeneties are more marked in recombinant cell cultures because subpopulations, which often exhibit different growth and productivity characteristics, are more easily identified by selective markers. A simple segregated mathematical model that simulates the growth of recombinantEscherichia colicells is developed. Subpopulations of different growth rate, plasmid replication rate, and plasmid segregation probability are explicitly considered. Results indicate that a third mechanism of plasmid instability, referred to here as a “downward selective pressure,” is significant when describing plasmid loss in batch and chemostat cultures. Also, the model agrees well with experimental data from cultures under antibiotic selective pressure. Finally, model simulations of chemostat cultures reveal the importance of initial conditions on culture stability and the possible presence of nonrandom partitioning functions. © 1993 John Wiley&Sons,

ISSN:0006-3592    

DOI:10.1002/bit.260420210

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe effect of the growth phase ofSpodoptera frugiperda(Sf9) cells on the production of recombinant proteins (β‐galactosidase and glucocerebrosidase) was investigated. Cells infected with the recombinantAutographa californicanuclear polyhedrosis virus at the late exponential and stationary phases yielded low quantities of expressed protein. Highest enzyme yields were obtained using Sf9 cells from the early exponential phase (0.9 mg β‐galactosidase/106cells and 1.7 μgglucocerebrosidase/106cells). Infection of resuspension of cells collected from various phases of growth in fresh medium resulted in 75% restoration of maximal expression levels. This finding suggested either nutrient limitation or waste product accumulation as the cause of the decrease in productivity at the latter phases of growth. Further experiments revealed that the highest productivity levels could be obtained with cultures of Sf9 cells grown in a fermentor to a cell concentration of 4 × 106mL−1. The medium needed to be replaced prior to infection with the recombinant virus and supplemented with a mixture of glucose, L‐glutamine, and yeastolate ultrafiltrate. © 1993 John Wil

ISSN:0006-3592    

DOI:10.1002/bit.260420211

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

年代:1993

数据来源: WILEY