摘要:

AbstractTheoretical and experimental studies concerning the application of modern adaptive techniques for the control of continuous alcoholic fermentation of glucose by a yeast strain conducted in a multistage reactor are reported. The practical control objective was the regulation of the substrate concentration in the process effluent. Mathematical expressions for the control scheme are given, with the underlying control engineering argumentation. Suitable feeding of sugar for stage 2 was controlled to minimize the effluent sugar concentration.

ISSN:0006-3592    

DOI:10.1002/bit.260350302

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

年代:1990

数据来源: WILEY

摘要:

AbstractIt is known that two microbial species competing for a single rate‐limiting nutrient cannot grow together in a chemostat under steady‐state operation, but eventually the species with the lower specific growth rate at the particular operating conditions will become extinct. Coexistence of the two populations has been shown obtainable in chemostats under periodic operation. This is possible in cases where the specific growth rate functions of the two species are such that for certain values of the nutrient concentration the first species grows faster than the second, and for other values of the nutrient concentration the second species is the one growing faster. In a previous article it was demonstrated that, even in cases where the specific growth rate functions of the two species are such that one of the species grows faster than the other for all values of the nutrient concentration, extinction of either species is possible provided that time delay in the response of the species to changes in their fermentation environment is accounted for, and that the faster growing species is also faster in its response. Here, we show that coexistence of the two species is also possible in a significant range of the operating parameters. We develop a numerical algorithm with which we trace the boundary of the coexistence region in the entire operating parameter space and construct the operating diagram of the sys

ISSN:0006-3592    

DOI:10.1002/bit.260350303

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

年代:1990

数据来源: WILEY

摘要:

AbstractIn an effort to develop an understanding of the interaction of inorganic carbon and light limitation in algal biofilms, a mathematical model was developed, based on well‐established mathematical descriptions of the biological, chemical, and physical processes involved. The results showed that the growth of algal biofilms is a very complex function of the inorganic carbon and light conditions, due to the interaction of inorganic carbon speciation with pH. These results are discussed in terms of the distribution of reaction rate through the biofilm and in terms of maximum potential growth rate for given bulk condition

ISSN:0006-3592    

DOI:10.1002/bit.260350304

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

年代:1990

数据来源: WILEY

摘要:

AbstractEnhancement of the productivity of xylanase and β‐xy‐losidase ofAspergillus ochraceuswas investigated by multistep mutagenesis. The spores of the wild strain were subjected to UV andN‐methyl‐N‐nitro‐N‐nitro‐soguanidine (NTG). The hyperxylanolytic mutant (NG‐13), which showed good clearing on the surface of the xylan‐agar plate, secretes xylanase and β‐xylosidase at high levels during growth on commercial xylan and on agricultural wastes. Both liquid and solid state cultures were employed in the study for enzyme production. The xylanase from NG‐13 was purified to homogeneity by ammonium sulfate precipitation and gel filtration. This purified enzyme showed a pH optimum of 6.0 and was stable in the range of pH 5 to 10. Prolonged stability of the enzyme was observed at 45°C though its activity was maximal at 50°C. The molecular weight of the enzyme was estimated to be 4.3 × 104by SDS‐polyacrylamide gel electrophoresis and 5 × 104by gel filtration on Sephadex G‐75. The kinetic data showed that theKmandVmaxvalues for xylan were 1 × 10−3Mand 19.6 μmol/ min/mg protein, respectively. The enzyme was both more active and thermostable in the presence of K+and was inactivated by thiol reagents such as Hg2+,p‐hydroxymercuribenzoate (PHMB), 3′, 5′‐dithiobis (2′‐nit

ISSN:0006-3592    

DOI:10.1002/bit.260350305

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

年代:1990

数据来源: WILEY

摘要:

AbstractThis article calculates optimal open‐loop temperature trajectories that maximize the average rate of product synthesis of a plant cell culture. It uses a previously published five‐state mathematical model which describes the growth and product synthesis of a batch plant cell suspension culture ofCatharanthus roseusunder temperature control. The optimal open‐loop temperatures maximize the final product concentration for predefined fermentation periods. A single switch in temperature is shown by computer simulation to be near optimal, with a 22% increase in final product yield over that obtained at the optimal constant temperature. Examination of the achieved final product yield as a function of fermentation period allows this period also to be chosen optimally. This time is reduced from 16 days in the constant temperature case to 12 days in the switched temperature

ISSN:0006-3592    

DOI:10.1002/bit.260350306

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

年代:1990

数据来源: WILEY

摘要:

AbstractIn this article we describe the use of bench‐scale single‐fiber dialyzers for the development and testing of an immobilized enzyme reactor for the treatment of leukemia. The treatment is based on the enzymatic removal of specific amino acids from the blood of leukemia patients.L‐Lysine α‐oxidase and catalase were coimmobilized within the void space of the porous region of asymmetric hollow‐fiber membranes for the removal ofL‐lysine from simulated human plasma solutions. Hollow‐fiber reactor performance was evaluated using a small single‐fiber dialyzer (SFD) consisting of a single fiber encased in a protective glass shell. This small reactor affords ease of use, requires small amounts of chemicals and biochemicals, and gives useful reactor performance data. Single‐fiber dialyzers were constructed using polyamide fibers with a molecular weight cutoff of 10,000 (PA10 fibers); these fibers demonstrated the best compatibility with and retention of the enzymes. The SFD performance in removingL‐lysine from solution was evaluated under both steady and pulsatile flow operation. Pulsatile flow was tested for two reasons: (1) to enhance the radial mass transfer of lysine within the SFD and (2) to simulate the pulsatile flow of blood in dialysis treatment. The use of pulsatile flow increased lysine conversion by 15% over the steady‐flow case. Approximately 40% of the lysine was removed from simulated plasma by the SFD in a 4‐h experiment using pulsatile

ISSN:0006-3592    

DOI:10.1002/bit.260350307

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

年代:1990

数据来源: WILEY

摘要:

AbstractLignin prepared by acid and enzyme hydrolysis of a softwood mixture adsorbs acetone, butanol, and other alcohols while showing only a slight uptake of glucose. Adsorption of butanol is independent of temperature in the range of 30‐65°C. The Polanyi theory fits adsorption for the linear alcohols methanol through hexanol with values of AS and Δμranging from 2.6 to 26 J mol−1K−1and −0.8 to −8 kJ/mol. The adsorption capacity is given by Q (g alcohol/g lignin) =KC*. WhereC*is the equilibrium alcohol concentration (g/mL),K= εWexp (Δ/R), and εwis the porosity of the lignin (0.23‐0.42 mL/g). The value of the adsorption capacity constantKforn‐butanol ranges from 1.3 to 2.7 mL/g on sorbent containing 26‐72% lignin, while ethanol is 0.5‐0.73, acetone is 0.62‐1.0, and glucose is 0.35. Adsorption is shown to occur through combined hydrophobic and hydrophilic interactions of the alkyl and hydroxyl groups, respectively, of the adsorbate with the lignin. Consequently, for the alcohols methanol to hexanol, we present the capacity constantK[=K(R) +K(OH)] as a sum of an alky! adsorption constant (0.1‐9.5 mL/g) and a hydrophilic (0.40‐0.50 mL/g) contribution. This approach may be applicable to organic acids. Lignin's sorbent properties have potential to moderate product inhibition in the anaerobic acetone‐but

ISSN:0006-3592    

DOI:10.1002/bit.260350308

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

年代:1990

数据来源: WILEY

摘要:

AbstractDiffusion of phenol through a biofilm attached to activated carbon particles was investigated. The biofilm was grown on activated carbon particles in a draft‐tube three‐phase fluidized‐bed bioreactor operating in a fed‐batch mode. It was found that phenol did not adsorb on the biofilm and that the diffusion coefficient of phenol within the biofilm varied from 13 to 39% of its corresponding value in water. The diffusion coefficient of phenol within the biofilm was reduced by increasing the biofilm density. An extensive literature review of diffusion of substrates through biofilms indicated that this conclusion could be extended to biofilms grown on flat surfaces, rotating cylinders, and even b

ISSN:0006-3592    

DOI:10.1002/bit.260350309

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

年代:1990

数据来源: WILEY

摘要:

AbstractA two‐stage continuous system in combination with a temperature‐sensitive expression system were used as model systems to maximize the productivity of a cloned gene and minimize the problem associated with the plasmid instability for a high‐expression recombinant. In order to optimize the two‐stage fermentation process, the effects of such operational variables as temperature and dilution rate on productivity of cloned gene were studied using the model systems and a recombinant,Escherichia coliK12 ΔH1 Δtrp/pPLc23trpA1. When the expression of cloned gene is induced by raising the operating temperature above 38°C, a significant decrease in the colony‐forming‐units (CFU) of the plasmid‐harboring cell was observed, and the decrease was related to the product concentration. In order to describe this phenomenon, a new kinetic parameter related to the metabolic stress (metabolic stress factor) was introduced. It is defined as the ratio of the rate of change of pheno‐type from colony‐forming to non‐colony‐forming cells to the product accumulation per unit cell mass. At a fixed temperature of 40°C, the varying dilution rateDin the range of 0.35‐0.90 h−1did not affect the metabolic stress factor significantly. At a fixed dilution rate ofD= 0.35 h−1, this factor remained practically constant up to 41°C but increased rapidly beyond 41°C. The effects of temperature and dilution rate in the second stage on the specific production rate were also studied while maintaining the apparent specific growth rate (μ 2app) of the second stage constant at or near μ 2app= 0.26 h−1. Under a constant dilution rate,D2= 0.35 h−1, the maximum specific production rate obtained was aboutqp, max= 38 units TrpA/mg cell/h at 41°C. At a constant temperature,T2= 40°C, specific production rate increased with decreasing dilution rate with in the dilution rate range ofD2= 0.35‐0.90 h−1. Based on the results of our study, the optimal operating conditions found were dilution rateD2= 0.35 h−1and operating temperatureT2= 41°C at the apparent specific growth rate of 0.26 h−1. Under the optimal operating conditions, about threefold increase in productivity was achieved compared to the best batch culture result. In addition, the fer

ISSN:0006-3592    

DOI:10.1002/bit.260350310

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

年代:1990

数据来源: WILEY

摘要:

AbstractSuspension cultures ofNicotiana tabacumwere grown in a batch fermentor using different agitation systems. The effects of the impeller type, size, and agitation speed on the productivity of cell mass and secondary metabolites (phenolics) have been investigated. The use of a large, flat‐bladed impeller (diameter 7.6 cm; width 14.0 cm) improved culture growth significantly over systems using a regular, flat‐bladed impeller (diameter 5.6 cm; width 1.5 cm). An impeller of the same dimensions as the 14.0‐cm‐wide, large, flat‐bladed impeller with sail cloth blades yielded a higher maximum growth rate in the exponential phase but resulted in a longer lag phase. Overall (intracellular and extracellular) phenolics concentration showed a direct relationship to culture growth rate whereas extracellular concentrations were a function of agitation conditions. Power consumption and flow pattern studies were also completed to further characterize the different impelle

ISSN:0006-3592    

DOI:10.1002/bit.260350311

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

年代:1990

数据来源: WILEY