摘要:

Abstractα‐Chymotrypsin was modified to a light‐controllable enzyme derivative by acylating active serine 195 residue with a cinnamoyl group or analogue. Upon UV irradiation the acylgroup could be isomerized, leading to release of the inhibiting group. Enzymatic activity could thus be regulated by means of UV light. A full 100% inhibition of the enzymatic activity could not be reached by the cinnamoyl derivative. Only posttreatment with diisopropylfluorophosphate yields a fully inactive enzyme derivative. The shelf‐life of the inhibited enzyme was rather poor. Only freeze‐dried samples could be used for several months without significant recovery of activity. Adapting the sensitivity of the system to visible light seems limited to the size of an enzyme's active site. Combination of the enzymatic system producing an inhibitor or an initiator with a polymerization reaction can result in a photographic process with a higher amplificatio

ISSN:0006-3592    

DOI:10.1002/bit.260290402

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe energy consumption of a fermenter constitutes a major part of the operating expense of a single cell protein process. A low‐pressure airlift fermenter was designed to reduce this cost. In this new design, the fermenter broth is kept below 120 cm in depth, and air alone is employed to fulfill the need of supplying oxygen, and cooling and agitating the broth. The use of low‐pressure air from air blowers instead of air compressors lowers the capital cost of air delivery and reduces the energy consumption in the fermenter section to below 1 kWh/kg protein, a saving of over 70% as compared to a conventional stirred tank fermenter. It also eliminates the investment of mechanical agitators, heat exchangers, and air compressors. Sulfite oxidation studies confirmed the design conce

ISSN:0006-3592    

DOI:10.1002/bit.260290403

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

年代:1987

数据来源: WILEY

摘要:

AbstractExperiments using Pichia yeast grown onn‐paraffins have been conducted in laboratory 10‐L airlift fermenters and in a 640‐L module of commercial scale. Results confirmed the design concept of combining oxygen transfer and fermenter cooling with low‐pressure air. However, in the absence of mass transport constraints, the build up of toxic factors in the fermenter appeared to be a major variable limiting cell productivity. Foaming in the large fermenter also presented a serious problem, which must be solved before low‐pressure airlift fermenters become

ISSN:0006-3592    

DOI:10.1002/bit.260290404

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

年代:1987

数据来源: WILEY

摘要:

AbstractAcetate, a by‐product of ethanol fermentation bySaccharomyces cerevisiae, has been shown to inhibit cell growth if present in high concentrations. Consequently, acetate has been considered undesirable in systems where the production rate depends upon steady‐state growth. Acetate, however, may be desirable in some systems since it increases the specific rate of ethanol production by increasing the maintenance requirements of yeast. In immobilized cell reactors using the crosslinking method, steady state is not achieved and cell overgrowth is a problem. This article presents the results of a study aimed at taking advantage of the use of acetate, both to reduce cell overgrowth and to increase productivity. Various concentrations of acetate were added to batch and plug flow systems, while monitoring the effects on cell growth and ethanol production. The productivity was increased by as much as 50% in an immobilized cell reactor (ICR), while cell growth was greatly redu

ISSN:0006-3592    

DOI:10.1002/bit.260290405

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe suitability of using annually grown, carrot‐sized buffalo gourd (Cucurbita foetidissima) roots as a feedstock for alcoholic fermentation was explored. Roots grown in 1982 and 1983 were slurried, dextrinized and saccharified using Takatherm™ and Diazyme™ (commercial enzymes manufactured by Miles Laboratories), and fermented by the action ofSaccharomyces cerevisiae. These processes were monitored in detail and results were compared with those displayed by controls formulated using potato tubers. The preparation of gourd root slurries with suitable viscosity characteristics for enzymatic digestion required the addition of water (at least 50% by weight) which reduced the proportion of fermentable sugars in the resulting saccharified suspensions. The resulting slurries were well‐suited to enzymatic conversion of starch to sugar. Estimates of enzymatic efficiency in gourd root suspensions did not suggest the presence of naturally occurring amylase or glucosidase inhibitors in these plant materials. Saccharified gourd root mashes supported yeast growth well and produced ethanol yields at 82.2–86.5% of the theoretically maximum e

ISSN:0006-3592    

DOI:10.1002/bit.260290406

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

年代:1987

数据来源: WILEY

摘要:

AbstractPowder and granular activated charcoal were evaluated for ethanol adsorptivity from aqueous mixtures using an adsorption isotherm. Ethanol adsorption capacity was more pronounced at 25°C as compared to 5, 15, and 40°C. When pH of the ethanol–buffer mixture (0.09 ionic strength) was changed from acidic (2.3) to neutral and then to alkaline (11.2), ethanol adsorption was decreased. Increasing ionic strength of the ethanol‐buffer mixtures from 0.05 to 0.09 enhanced ethanol adsorption but a further increase to 0.14 showed no significant effect. Ethanol adsorption was more efficient from an aqueous ethanol mixture as compared to semidefined and nondefined fermentation worts, respectively. Heating granular charcoal to 400°C for 1 h and 600°C for 3 h in N2increased ethanol adsorptivity and heating to 1000°C (1 h) in CO2decreased it when ethanol was removed from dilute solutions by simple pass adsorption in a carbon packed column. Granular charcoal was superior to powdered charcoal and an inverse relationship was noted between the weight of the granular carbon bed in the column and ethanol adsorbed/g carbon. Decreasing the column feed flow rate from 7.5 to 2.0 L aqueous ethanol/min increased the adsorpt

ISSN:0006-3592    

DOI:10.1002/bit.260290407

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe yeastCandida utilisand the bacteriumEscherichia coliB/r were evaluated as a candidate experimental, continous, competitive mixed culture system under ammonia–nitrogen limited conditions at 30°C. High dilution rates favored yeast dominance, while low dilution rates favored bacterial dominance. The hydrogen ion concentration was also demonstrated to be an effective manipulative variable for control of the yeast–bacterial mixed culture. Through trial‐and‐error manipulation of the pH for the mixed culture operating at constant dilution rate, it was possible to locate a metastable equilibrium point and to operate in the vicinity of that point for more than 24h. The reproducible emergence of a variantE. coliwas also noted in th

ISSN:0006-3592    

DOI:10.1002/bit.260290408

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe soil yeastTrichosporon cutaneumwas grown in continuous culture with phenol as the sole carbon source. The cultures were operated as carbon‐limited chemostats or as steady‐state continuous cultures without carbon limitation. Selected comparative runs were also conducted on glucose or acetate as carbon source. In addition to growth parameters, the activities of several intracellular enzymes were determined, comprising those directly involved in the degradation of phenol as well as auxiliary enzymes required for the generation of reducing power. All enzymes were assayed in detergent‐permea‐bilized cells. Phenol was found to serve as an excellent carbon source, comparable to glucose or acetate. The utilization of phenol inT. cutaneumis very efficient as indicated by a low maintenance requirement (0.01 g phenol/g cells·h). The cell yields obtained were on the order of 0.8 g cells/g phenol. Although the phenol‐limited chemostats were run with fully phenol‐induced cells, a further increase in the activities of isocitrate DH(NADP+), maleate DH and the phenol‐degrading enzymes occurred after transition to nonlimiting condition. Enzyme activities increased in parallel with increasing phenol levels in the effluent, as well as with increasing toxicity. The significance of this phenomenon is discussed. The significance of this phenomenon is discussed. This elevation in enzyme activities in not related to an increase in specif

ISSN:0006-3592    

DOI:10.1002/bit.260290409

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

年代:1987

数据来源: WILEY

摘要:

AbstractA major problem in the use of plasmids as recombinant vectors is the problem of plasmid‐free cell generation from plasmid shedding and subsequent growth. A common technique for controlling the population of plasmidfree cells is the use of selective media against these cells using an auxotrophic host and a plasmid that has the ability to produced the essential metabolite. A distributed model describing the growth ofSaccharomyces cerevisiaecontaining a recombinant plasmid in selective media was developed. The model allows for growth and production of a metabolite by the plasmid‐carrying strain and growth of the plasmid‐free cells on resulting metabolite concentrations. Through a determination of system constants and numerical solution to the equations, experimental batch and continuous culture results for cell concentration transients could be simulated by the model. The results indicated that despite selective pressure, plasmid‐free cell growth was sign

ISSN:0006-3592    

DOI:10.1002/bit.260290410

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

年代:1987

数据来源: WILEY

摘要:

AbstractAvailable electron methods are presented and used to estimate theoretical energetic growth yields for photoautotrophic, mixotrophic, and photoheterotrophic growth of algae and photosynthetic bacteria. The theoretical yields are compared to experimental values reported previously. For photoautotrophic and mixotrophic growth of algae experimental values that approach and even exceed the theoretical values have been reported in the literature. For photosynthetic bacteria experimental yields are much smaller than thetheoretical maximum values.

ISSN:0006-3592    

DOI:10.1002/bit.260290411

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

年代:1987

数据来源: WILEY