摘要:

AbstractThe optimal glucose feeding policy for the fed‐batch culture ofSaccharomyces carlsbergensisis presented. The biphasic nature of growth results in a singular feed rate policy that is unique to this organism. When the operating cost is high, the reduction in operating time forces the cells to utilize both glucose and ethanol toward the end of fermentation time and results in a decreasing rate of glucose addition, unlike the normally observed in creasing feed rate. The optimal feeding policy depends heavily on the initial conditions and is highly sensitive to changes in kinetic parameters. A semiempirical scheme for feedback optimization is suggested for the fed‐batch yeast cult

ISSN:0006-3592    

DOI:10.1002/bit.260330102

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

年代:1989

数据来源: WILEY

摘要:

AbstractDetermination of the optimal feed rate for fed‐batch fermentation is normally a problem in singular control with a state inequality constraint and as such is, in general, difficult to solve, especially for those described by a large number of dynamic mass balance equations. In this article we use a new set of state variables and the culture volume as the control variable. In this way the problem is converted to one of nonsingular control with the magnitude and rate constraints on the manipulated variable and can be numerically solved by a gradient‐based technique, thus avoiding the difficulty associated with singular control problems. Examples are given to illustrate the met

ISSN:0006-3592    

DOI:10.1002/bit.260330103

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

年代:1989

数据来源: WILEY

摘要:

AbstractA multivariable adaptive optimization algorithm that uses transient data to improve the optimization speed was successfully implemented on‐line to maximize the steady‐state cellular productivity of a continuous culture of baker's yeast. The algorithm was shown to be stable even during periods of oscillatory growth and was able to reoptimize the culture when planned disturbances were introduced. Although adaptive tuning of the forgetting factor improved the performance, further refinements in the adaptive forgetting factor algorithm are necessary for completely satisfactory resu

ISSN:0006-3592    

DOI:10.1002/bit.260330104

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe conditions for the introduction of active carbonate groups into supports containing hydroxyl groups by reaction with 5‐norbornene‐2.3‐dicarboximido carbonochloridate are described. Up to 1.5 mmol carbonate groups/g dry Sepharose 4B could be bound. In the case of glycine the reaction of the activated supports with the amino groups takes place with a 10‐fold higher rate than the hydrolysis of the carbonate groups, and high coupling yields can be reached. It is shown that the activated supports are well suitable for the preparation of carriers for affinity chromatography or the immobilization of

ISSN:0006-3592    

DOI:10.1002/bit.260330105

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe anoxic–oxic activated‐sludge process has been evaluated in a laboratory investigation as a means for effective treatment of cyanide‐laden wastewaters, with phenols used as the organic carbon sources for denitrification reactions. The performance of the process was evaluated at different levels of feed cyanide concentration and mean cell residence time (MCRT). The results obtained indicate that the phenolic compounds used can be effectively used as the organic carbon sources to promote denitrification reactions. The effects of cyanide inhibition on overall TOC removal can be alleviated at longer MCRTs. Between 1.2 and 2.2 g TOC can be utilized per gram NO2+ NO3−‐N removed in the anoxic chamber depending on the prevailing MCRT. Microbial oxidation of cyanide and thiocyanate which yields ammonia is the main mechanism responsible for the removal of cyanide and thiocyanate observed in the anoxic–oxic activated‐sludge process. Excellent removal efficiencies have been observed with feed concentrations up to 60 mg CN−/L and 100 mg SCN−/L Frequent exposure of autotrophic and aerobic cyanideutilizing microbes does not impede their activities in the oxic environment. Good nitrification and denitrification efficiencies are attainable in the anoxic–oxic activated‐sludge process in the presence of high feed cyanide and thiocyanate concentrations, provided that MCRT is maintained at a desirable level. As a result, the microbial degradation of cyanide and thiocyanate in conjunction with nitrification and denitrification to produce innocuous nitrogen gas is feasible in the anoxic–oxic a

ISSN:0006-3592    

DOI:10.1002/bit.260330106

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

年代:1989

数据来源: WILEY

摘要:

AbstractVarious experimental procedures for the determination of transient characteristics with significant liquid film effects were tested. A comparison between transient characteristics obtained experimentally and those calculated from rational models indicates that all procedures but one give highly inconsistent results. Recalculation of transient characteristics with no liquid film (easily measured in the gas phase) to that with liquid film (occurring in viscous liquids) is recommended as well as the selected experimental procedure which yields consistent results in the situations where the steady‐state probe reading is decreased up to one‐half due to the liquid f

ISSN:0006-3592    

DOI:10.1002/bit.260330107

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe instantaneous specific growth rate of a recombinant bacterial culture is directly calculated using a simple structured kinetic modeling approach. Foreign plasmid replication and foreign protein expression represent metabolic burdens to the host cell. The individual effects of these plasmid‐mediated activities on the growth rate of plasmid‐bearing cells are estimated separately. The dynamic and steady state simulations of the model equations show remarkable agreement with widely observed experimental trends in plasmid copy number and foreign protein content. The model provides an important tool for understanding and controlling plasmid instability in recombinant bacterial fermentations. The modeling framework employed here is suitable for studying the metabolism and growth of a variety of microbial cultu

ISSN:0006-3592    

DOI:10.1002/bit.260330108

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

年代:1989

数据来源: WILEY

摘要:

AbstractSeveral independent experimental techniques, including nondenaturing and denaturing isoelectric focusing, spin labeling, and enzyme immobilization, indicate that four ethanol‐active subunits of horse liver alcohol dehydrogenase (LADH) can be classified as one of two types, designatedE1andE2. Thermal inactivation studies of LADH in solution and immobilized to two different supports demonstrate that the first‐order rate constants of deactivation ofE1andE2differ by more than an order of magnitude. Furthermore,E1, andE2can be distinguished by EPR spectroscopy, with the less stable subunit type,E2, appearing to have the less compactly structured active‐site environment. The less stable enzyme form also loses catalytic activity upon covalent attachment to CNBr‐Sepharose but remains active when adsorbed to Octyl‐Sepharose. Moreover, the immobilization results in conjunction with lysine modification studies suggest thatE2immobilized to CNBr‐Sepharose cannot bind coenyzme. Overall, these results illustrate how EPR measurements in concert with activity assays can pro vide insights into the molecular mechanisms of enzyme st

ISSN:0006-3592    

DOI:10.1002/bit.260330109

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

年代:1989

数据来源: WILEY

摘要:

AbstractA bacterial strain,Bacillus licheniformis, has been isolated and identified which produces high‐temperature alkaline α‐amylase. Cultural conditions, such as types of carbon and nitrogen sources, temperature, pH, and time of reaction, have been optimized for production of α‐amylase in shake flask and fermenter. The enzyme produced was quite active even at 100°C; however, it showed optimum activity at 90°C. It exhibited optimum activity in the broad pH range 5.5–10. The effects of Na+and Ca2+ions on enzyme activity was a

ISSN:0006-3592    

DOI:10.1002/bit.260330110

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

年代:1989

数据来源: WILEY

摘要:

AbstractCalcium alginate gel beads were prepared from a range of well characterized alginates. The physical properties of beads depended strongly on the composition, sequential structure, and molecular size of the polymers. Beads with the highest mechanical strength, lowest shrinkage, best stability towards monovalent cations, and highest porosity were made from alginate with a content ofL‐guluronic acid higher than 70% and an average length of the G‐blocks higher than 15. For these “high G” alginates the critical overlap intrinsic viscosities have been determined, and for molecular weight higher than 2.4 × 105, the gel strength was independent of the molecula

ISSN:0006-3592    

DOI:10.1002/bit.260330111

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

年代:1989

数据来源: WILEY