摘要:

AbstractA fermentation process for the microbial production of an amphipatic lipopolysaccharide, emulsan, has been established using a triglyceride carbon source in a coordinated carbon–nitrogen feed strategy. The polysaccharide was produced by theAcinetobacterstrain at a productivity of about 0.5 g emulsan/L h while utilizing only the fatty acids (FA) portion of the triglycerides or free fatty acids that were fed into the medium.A useful correlation between the utilization of the fatty acids and the consumption of the nitrogen was found and employed for the practical feed strategy using an appropriate CN ratio (7.7 g C/g N) of the soybeanoil (SBO) (carbon source) to the ammonium hydroxide base (nitrogen source). Either the pH control or the supervising computer system could accomplish the adequate balanced feed in to the fermentor. Lipolysis slowdown was overcome by switching from a triglyceride carbon source to a free fatty acids one. A yield of about 0.2 g emulsan/g fatty acids was obtained and a final concentration of over 20 g/L was reached. The polymeric product was found to be partially associated with the cell‐oil complexes in the fermentation broth unless the oily carbon source was efficiently exhausted. A fedbatch fermentation that employed a shift of the carbon source feed from triglycerides to free fatty acids appeared to be an appropriate and feasible way of producing the po

ISSN:0006-3592    

DOI:10.1002/bit.260350802

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

年代:1990

数据来源: WILEY

摘要:

AbstractImportant aspects ofklameasurement in agitated aerated vessels are briefly characterized from the standpoint of reliability of the measured data. It seems that most of thekladata, based on a number of variants of the steady‐state and dynamic methods in noncoalescent liquids, do not have a clear physical meaning, because they are affected by the differences between the actual driving force and the driving force assumed by the model used for its evaluation. A reliability test is given for the Na2SO3feeding steady‐state method (FSM), by comparing the results of air and pure oxygen absorption in a noncoalescent liquid (0.5MNa2SO4solution) with the results obtained by the independent pressure step dynamic method (RDM). The RDM is one of a few variants of the dynamic method which gives correctkladata unaffected by nonideal mixing of the gas phase in the reactor. It was found that the FSM yields correctklavalues only when pure oxygen is used for absorption. When air is absorbed, the FSM givesklavalues in the region ofkla>0.1 s−1substantially (to 55%) lower than those for pure oxygen absor

ISSN:0006-3592    

DOI:10.1002/bit.260350803

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

年代:1990

数据来源: WILEY

摘要:

AbstractRegulated secretion, i.e., the ability of certain specialized animal cells to store secretory proteins intracellularly and release them upon stimulation, may be used to realize production schemes that facilitate downstream processing of protein products. Mouse AtT‐20 cells expressing recombinant human insulin and human growth hormone (hGH) were found to secrete the proteins at relatively low and constant rates when exposed to media with no secretion agonists: basal rates were 1.0–1.6 μU insulin‐reiated peptides and 0.38 ng hGH/105cells‐h. When induced with 8 brorno‐cyclic AMP (BrcAMP), the cells secreted recombinant proteins at initial rates 3.5–9‐fold higher. A cycling secretion experiment was conducted with the insulin‐producing cells in which the cells were exposed alternately to complete growth medium and to secretion medium with BrcAMP. During the first three cycles, the cells secreted immunoreactive insulin at the foregoing high induced rates when they were exposed to BrcAMP. The cells then started to detach from the culture surface, leading to a reduction of BrcAMP‐induced secretion. Operational modifications that may result in improved system perform

ISSN:0006-3592    

DOI:10.1002/bit.260350804

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

年代:1990

数据来源: WILEY

摘要:

AbstractSomatic embryos in liquid culture can serve as a mass cloning system in a plant propagation program. A quantitative formulation of embryo development obtained from cell suspension cultures is used to develop a segregated kinetic model. The model is based on standard classification schemes as previously developed by plant physiologists. Dependent variables include carbohydrate concentrations (sucrose, fructose, and glucose) and biomass apportioned among the inoculum (free single cells, cell clusters), normal developmental stages, and aberrant cell and embryo types. Good agreement between the model and experimental results is indicated and allows for a rigorous approach to media optimization and reactor scaleup for embryo formation.

ISSN:0006-3592    

DOI:10.1002/bit.260350805

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

年代:1990

数据来源: WILEY

摘要:

AbstractGas chromatography/mass spectrometry was used to detect the presence ofEnterobacter cloacaein cultures ofLeuconostoc mesenteroides, an organism used in an industrial process for production of dextrane. The penta‐fluorobenzoyl‐methyl ester derivative of 3‐hydroxy‐myristic acid, a characteristic compound of gram‐negative bacteria, was used as the analyte. By using gas chromatography/mass spectrometry with selected ion monitoring,E. cloacaewas determined over the range of 1 ppm to 1% in cultures ofL. mesenteroides.The proposed analytical approach represents a useful alternative to conventional methods for determining contaminating organisms in industrial fermentation

ISSN:0006-3592    

DOI:10.1002/bit.260350806

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe activities of lipase fromCandida cylindraceaandRhizopus delemarhave been investigated in water/AOT/iso‐octane reverse micellar media through the use of two esterification reactions: fatty acid‐alcohol esterification and glyceride synthesis. Such media promotes the occurrence of these two lipase‐catalyzed reactions due to its low water content. The effect of various parameters on the activity of lipase fromC. cylindraceain reverse micelles was determined and compared to results where alternate media were employed. It was observed that the structure of the media, as dictated by the type and concentration of the substrates and products and by the water/AOT ratio,w0, had a strong impact on enzyme activity. Strong deactivation of both typase types occurred in reverse micelles, especially in the absence of substrates and forw0values greater than 3.0. Glyceride synthesis was realized with lipase fromR. delemar, but not with that fromC. cylindracea; the temperature and concentration of substrates and water strongly dictated the reaction rate and the percent conve

ISSN:0006-3592    

DOI:10.1002/bit.260350807

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

年代:1990

数据来源: WILEY

摘要:

AbstractA mathematical model was developed and tested to simulate the generation and transfer of heat in solid substrate fermentation (SSF). The experimental studies were realized in a 1‐L static bioreactor packed with cassava wet meal and inoculated withAspergillus niger. A simplified pseudohomogeneous monodimensional dynamic model was used for the energy balance. Kinetic equations taking into account biomass formation (logistic), sugar consumption (with maintenance), and carbon dioxide formation were used. Model verification was achieved by comparison of calculated and experimental temperatures. Heat transfer was evaluated by the estimation of Biot and Peclet heat dimensionless numbers 5–10 and 2550–2750, respectively. It was shown that conduction through the fermentation fixed bed was the main heat transfer resistance. This model intends to reach a better understanding of transport phenomena in SSF, a fact which could be used to evaluate various alternatives for temperature control of SSF, i.e., changing air flow rates and increasing water content. Dimensionless numbers could be used as scale‐up criteria of large fermentors, since in those ratios are described the operating conditions, geometry, and size of the bioreactor. It could lead to improved solid reactor systems. The model can be used as a basis for automatic control of SSF for the production of valuable metabolites in static fer

ISSN:0006-3592    

DOI:10.1002/bit.260350808

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

年代:1990

数据来源: WILEY

摘要:

AbstractA model describing growth of an outdoor algal (Spir‐ulina platensis)culture was developed. The model can simulate biomass production, pH, growth rate, oxygen evolution, and CO2fixation rate. It was calibrated and validated against experimental data obtained by a novel automatic data logger/controller instrumentation which can number most vital parameters of the culture including on line estimation of oxygen production rate (OPR). The importance of understanding light distribution through the pond and its effects on the photosynthesis and respiration processes are emphasized. A maximum yield of about 38g day−1m−2under optimal conditions is predicted. The present model can also be a useful tool for optimization of algal mass production

ISSN:0006-3592    

DOI:10.1002/bit.260350809

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

年代:1990

数据来源: WILEY

摘要:

AbstractA new kinetic model is developed which provides a simple quantitative description of the growth of mycelial organisms. The main concept of this model is that the fungal hypha can be regarded as a form of self‐extending tubular reactor. Nutrients are absorbed along the length of the “reactor,” converted into cell envelope precursors and transported forward to the growth tip where they become consumed in the process of extension; Michaelis–Menten kinetics are assumed to operate at this point. The model is capable of predicting changes in the rates of hyphal extension, branching, and fragmentation during mycelial growth in submerged culture and consequently variations in the hyphal growth unit. Simulation studies using the model are presented and the results are evaluated with reference to data from an industrial‐type fed‐batch penicillin f

ISSN:0006-3592    

DOI:10.1002/bit.260350810

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

年代:1990

数据来源: WILEY

摘要:

AbstractComplex coacervation is a phenomenon of phase separation that may occur in a solution of positively and negatively charged polyions. The resulting two phases are distinguished by the total concentration of both polyions, with the concentrated phase often containing vesicular structures composed of the two polyelectrolytes. We have used this phenomenon in an attempt to‐prepare a hemoglobin‐based red blood cell analog. Hemoglobin‐containing coacervate vesicles have been prepared from gelatin A and the polyanionic carbohydrates acacia, pectin, or dextranstilfate. Hemoglobin seems to be anchored into the vesicle walls through interaction of its polyanion binding site with the negatively charged residues on the carbohydrates. Oxygen binding by the immobilized HbA is reversible and cooperative, with p50 values at 20°C of 2.8, 6, and 24 mm Hg for the acacia‐ (pH 7.5), pectin‐ (pH 6.6), and dextransulfate‐(pH 6.6) derived coacervates. Kinetic studies on CO binding show that the rate of CO uptake by the coacervates (t½= 13–27 ms at 0.5 mMCO) is similar to that of human erythrocytes.The HbA‐containing coacervates slowly dissolve in isotonic salt solutions (145 mMNaCl, pH 7.4), but they can be stabilized by treatment with glutaraldehyde. Oxygen binding by HbA incorporated into the stabilized coacervates derived from dextran sulfate is very similar to oxy gen binding by human red blood cells: p50 = 26 mm Hg andn= 1.89 at 37°C in isotonic salt. These results show how a novel approach, based on an old concept, has led to the preparation of immobilized HbA, with functional properties similar to those of int

ISSN:0006-3592    

DOI:10.1002/bit.260350811

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

年代:1990

数据来源: WILEY