A simulation model for the continuous production of acetoin and butanediol using Bacillus subtilis with integrated pervaporation separation

The potential for producing acetoin and butanediol with a Bacillus subtilis strain was investigated with continuous culture using molasses as carbon substrate. The steady-state results were influenced by both oxygen and undetermined limiting compounds. Employing the known metabolic pathways, four overall stoichiometry relations were used with an energetic assumption on the energy requirements for biomass formation to establish a linear relations were used with an energetic assumption on the energy requirements for biomass formation to establish a linear relation between the overall rates, whose parameters were determined by linear regression. This provided a relationship for the product formation rate. The chemostat culture data were described with a growth kinetics model, which included limitation by molasses and oxygen as well as diauxic effects and product inhibition. The biokinetics model was combined with an experimentally verified model for the membrane Pervaporation. From this combined model were determined the influence of the membrane characteristics (enrichment factors and membrane area) and the dilution rate on the performance of the integrated process. Simulations revealed that an increase of the enrichment factor, possible by membrane improvement, would have counteracting influences, owing to decreased product inhibition but with lower biomass concentration. (c) 1993 Wiley & Sons, Inc.     

Advance directives: the views of health care professionals.

OBJECTIVES: This study examined the views and experiences of 20 physicians and 20 nurses at a major Canadian teaching hospital regarding the use of advance directives in clinical care. DESIGN: The participants were purposively drawn from four clinical specialties: family and community medicine, oncology, intensive care and geriatrics. Detailed interviews were conducted in person. Content analysis was used to code the data, which were further analysed with both quantitative and qualitative techniques. MAIN RESULTS: Thirty-nine of the 40 participants favoured the use of advance directives in clinical care; physicians had somewhat less positive attitudes than nurses toward such directives. Advance directives were thought by participants to be helpful in resolving disagreements between patients and their families about treatment options; in making patients more comfortable, both physically and psychologically, during the process of dying; and in opening up communication and trust among patients, their families and health care professionals. Concerns about the use of advance directives focused on the lack of clarity in some patients'' instructions, the absence of legal status for directives, the possible interference with a practitioner''s clinical judgement, the adequacy and appropriateness of patients'' information about their circumstances, and the type of intervention (passive or active) requested by patients. CONCLUSIONS: New regulations and legislation are making the use of advance directives more widespread. Health care professionals should participate in the development and implementation of these directives. Continuing professional education is essential in this regard.     

Trade-offs and seasonal variation in territorial defence and predator evasion in the European Robin Erithacus rubecula

The low incidence of intraspecific combat in territorial systems has traditionally been accounted for by theories that emphasize the bio-energetic advantages or the diminished risk of injury of threat display posture when compared with combat. Recently, however, it has been suggested that territory-holding passerines engaging in highly aggressive defensive behaviour are likely to pay a cost in terms of reduced vigilance for avian predators. To examine this further, two defensive options (combat and threat display) were evoked and observed in territorial European Robins Erithacus rubecula , in both winter and summer. It was found that Robins that engaged in combat during simulated territorial intrusion were significantly slower to react to a stuffed Sparrowhawk Accipiter nisus , than those eliciting threat display. Therefore, the decreased vigilance in escalated fighting may result in higher vulnerability to predation, and this might help, in part, to explain why threat display is favoured over direct combat. Moreover, the mean time to evade the predator was significantly longer in summer than in winter in threat-displaying Robins. In addition to this finding, a clear difference in the type of behaviour adopted between the seasons was observed, with lower incidence of combatative response during the winter months. This difference in response to the appearance of a predator is discussed in relation to reduced levels of safe cover, a reduction in the availability of alternative prey during the winter months and to seasonal fluctuations in plasma androgen levels.     

Purification, biochemistry and molecular cloning of an insect glycosylasparaginase from Spodoptera frugiperda

Glycosylasparaginase (EC 3.5.1.26 [EC] ) from Sf9 cells (Spodopterafrugiperda) was purified to homogeneity with a specific activityof 2.1 unit/mg. The enzyme is composed of two non-identical     

Massive fungal contamination in animal care facilities traced to bedding supply.

During the course of immunologic studies involving the gastrointestinal colonization of mice with Candida albicans, it became apparent that the animals were being exposed to large numbers of Aspergillus fumigatus spores which interfered with the C. albicans colonization. To determine the source of the A. fumigatus exposure and the extent of fungal contamination of the medical school vivarium and four satellite facilities, fungal analyses of feed, bedding, and air were undertaken. Initial samples from the air were collected with 3-h settle plates; air sampling following cleanup was done with an Anderson air sampler. The source of contamination in the mouse rooms was determined to be Beta Chip bedding, which came from the manufacturer highly contaminated. Beta Chip bedding (1 g) obtained from the manufacturer just prior to testing contained 10(4) CFU of A. fumigatus, 20 CFU of a zygomycete, and 10 CFU of a Penicillium sp. Coarse-grade Beta Chip had approximately one-half those levels of contamination. Pure Cob bedding was highly contaminated also, but with a Fusarium sp. and a Cladosporium sp. Untreated and heat-treated Sani-Chip as well as all other heat-treated preparations obtained from the manufacturer contained no detectable spores. Rodent chow direct from the manufacturer had no A. fumigatus, although it did contain 150 CFU of fungus per g, including 80 CFU of a Rhodotorula sp., 60 CFU of Cryptococcus uniguttulatus, and 1 CFU of a Penicillium sp.(ABSTRACT TRUNCATED AT 250 WORDS)     

The synthesis, purification, and evaluation of a chromophoric substrate for pepsin and other aspartyl proteases: design of a substrate based on subsite preferences

A convenient chromophoric assay for porcine pepsin has been developed using a new synthetic substrate. The sequence of this substrate was chosen based on the known subsite preferences for this enzyme. The peptide contains a phenylalanyl-p-nitrophenylalanine sequence at the reactive site. Cleavage of this bond yields a change in absorbance at 310 nm of between 1700 and 2000 per mole. This allows kinetic data to be obtained readily and accurately. The products of cleavage have been identified by isolation of a peptide fragment by high-performance liquid chromatography. Values of kcat, Km, and kcat/Km of 94 +/- 6 s-1, 0.13 +/- .04 mM, and 815 +/- 210 s-1/mM-1 were obtained at pH 3.0 and 37 degrees C. The peptide is soluble over the pH range from 2 to 7, thus facilitating determination of the pH dependence of the kinetic parameters. The substrate is also valuable in studying the inhibition of pepsin.     

Association of gap junctions with endoplasmic reticulum in rat parotid glands

Summary Examination of the parotid gland of the rat has shown specific associations of cisterns of the endoplasmic reticulum with gap junctions. About 20% of the junctions are so intimately associated with cisterns of the endoplasmic reticulum that in freeze fractured material the cisternal membranes remain attached to the junctional membrane faces, obscuring most of the junctional array except for a thin ring of telltale particles. This association was seen only in the parotid gland of the rat, but not that of the other species examined.     

Production of erythropoietin in vitro: A review

Summary The in vitro production of the important regulatory of erythropoiesis, erythropoietin (Epo), is reviewed. It is concluded that it is possible to produce almost routinely small quantities of Epo in tissue culture. Although such procedures offer the potential to provide large quantities of the hormone for clinical use, the optimum culture conditions and mechanisms for triggering Epo production have yet to be resolved. This work was supported by Grants No. 74444 from The John A. Hartford Foundation, and HL 10567 from the National Institutes of Health.