Glucose oxidation in a dual hollow fiber bioreactor with a silicone tube oxygenator

A dual hollow fiber bioreactor, consisting of an outer silicone membrane for oxygen supply and an inner polyamide membrane for substrate permeation, was used as an immobilized enzyme reactor to carry out enzymatic glucose oxidation. Attaching a silicone tube oxygenator to provide an additional oxygen supply improved the conversion in glucose oxidation when the oxygen supply was rate-limiting. The reactor was operated in both diffusion and ultrafiltration modes. In the latter case, the conversion was much higher, but the stability of the immobilized enzyme was better maintained in the diffusion mode. As the inlet glucose concentration increased from 10mM to 500mM, the conversion decreased from 70 to 20%.     

Distinct lipoxygenase species appear in the hypocotyl/radicle of germinating soybean

Three lipoxygenase isozymes are synthesized in developing soybean (Glycine max [L.] Merr. cv Williams) embryos and are found in high levels in cotyledons of mature seeds (B Axelrod, TM Cheesbrough, S Zimmer [1981] Methods Enzymol 71: 441-451). Upon germination at least two new protein species appear which are localized mainly (on a protein basis) in the hypocotyl/radicle section. These lipoxygenase species appear also in seedlings of each of three lipoxygenase nulls (1×1, 1×2, and 1×3) deficient in one of the dormant seed lipoxygenases. The germination-associated species are distinguishable from dry seed lipoxygenase by their more acidic isoelectric points as revealed in isoelectric focusing gels. They are active from as early as 2 to at least 5 days after the start of imbibition. These germination-stimulated species qualify as lipoxygenase by their inhibition by the lipoxygenase inhibitors n-propyl gallate and salicyl hydroxamic acid and their lack of inhibition by KCN. Further, they are not active on the peroxidase substrate pair H₂O₂/3-amino-9-ethyl carbazole. They are recognized on Western blots by polyclonal antibodies to the seed lipoxygenase-1 isozyme and the major induced species has a molecular weight of approximately 100,000, similar to that of the cotyledon lipoxygenases. These lipoxygenases appear to be synthesized de novo upon germination since they comigrate with radioactive protein species from seeds germinated in [³⁵S]methionine.     

Evidence and bioassay for diuretic factors in the nervous system of larvalHeliothis virescens

Summary Diuretic factors were studied in the central nervous system of larvae of the tobacco budworm,Heliothis virescens, using [¹⁴C]urea as a sensitive indicator for water movement through isolated Malpighian tubules. The assay required Na⁺ and a pH of 6.0–6.2 for maximum activity. Malpighian tubules had high secretory activity in feeding larvae of the fifth instar, but the activity declined during the burrowing-digging stage that preceded pupation. Malpighian tubules from starved larvae showed a greater response to extracts of nervous tissues than did tubules from feeding larvae, and extracts showed a dose-response relationship with fluid secretion. Diuretic activity was distributed throughout all parts of the central nervous system with the brain having the most activity. Brain extracts increased fluid secretion by in vitro Malpighian tubules by more than 3-fold and doubled the rate of dye clearance from the hemolymph in vivo. Diuretic activity in nervous tissue extracts was unaffected by boiling but sensitive to proteases. Fluid secretion by in vitro tubules was increased by cAMP, dbcAMP, theophylline, octopamine and dopa. These studies provide evidence for the presence of diuretic factors in the central nervous system ofH. virescens larvae and describe a sensitive bioassay for these factors.Abbreviations AR activation ratio - cAMP cyclic AMP - dbcAMP dibutyryl cyclic AMP - dbcGMP dibutyryl cyclic GMP - Dopa dihydroxyphenylalanine - 5-HT 5-hydroxytryptamine - L1 larval instar - VCNS ventral central nervous system     

The cloned human oestrogen receptor contains a mutation which alters its hormone binding properties.

We demonstrate here that the human oestrogen receptor (hER) cDNA clone pOR8 obtained from MCF-7 cells contains an artefactual point mutation which results in the substitution of a valine for a glycine at amino acid position 400 (Gly-400----Val-400). This mutation in the hormone binding domain of the cloned hER destabilizes its structure and decreases its apparent affinity for oestradiol at 25 degrees C, but not at 4 degrees C, when compared with the wild-type hER with a Gly-400.     

The lyotropic liquid crystal properties of n-octyl 1-O-beta-D-glucopyranoside and related n-alkyl pyranosides

X-ray diffraction patterns have been obtained for the lyotropic phases of n-octyl 1-O-beta-D-glucopyranoside and the related n-heptyl, n-nonyl and n-decyl compounds with water. The octyl compound exhibits all three liquid crystal phases and forms a micellar solution with increasing solvation, when the crystal come into contact with water at room temperature. The X-ray diffraction patterns show a one-dimensional lamellar phase with [dx] = 28.4 A, a three-dimensional face-centered cubic phase with [a] = 51.2 A, and a two-dimensional hexagonal phase with [a] = [b] = 36.7 A. The micellar solution has a distribution pattern with a maximum at [dx] = 33.8 A. Crystals of the heptyl, nonyl and decyl derivatives form only the lamellar phases and the micellar solution on contact with water at room temperature.     

Acetone-butanol-ethanol (ABE) fermentation in an immobilized cell trickle bed reactor

Acetone-butanol-ethanol (ABE) fermentation was successfully carried out in an immobilized cell trickle bed reactor. The reactor was composed of two serial columns packed with Clostridium acetobutylicum ATCC 824 entrapped on the surface of natural sponge segments at a cell loading in the range of 2.03-5.56 g dry cells/g sponge. The average cell loading was 3.58 g dry cells/g sponge. Batch experiments indicated that a critical pH above 4.2 is necessary for the initiation of cell growth. One of the media used during continuous experiments consisted of a salt mixture alone and the other a nutrient medium containing a salt mixture with yeast extract and peptone. Effluent pH was controlled by supplying various fractions of the two different types of media. A nutrient medium fraction above 0.6 was crucial for successful fermentation in a trickle bed reactor. The nutrient medium fraction is the ratio of the volume of the nutrient medium to the total volume of nutrient plus salt medium. Supplying nutrient medium to both columns continuously was an effective way to meet both pH and nutrient requirement. A 257-mL reactor could ferment 45 g/L glucose from an initial concentration of 60 g/L glucose at a rate of 70 mL/h. Butanol, acetone, and ethanol concentrations were 8.82, 5.22, and 1.45 g/L, respectively, with a butanol and total solvent yield of 19.4 and 34.1 wt %. Solvent productivity in an immobilized cell trickle bed reactor was 4.2 g/L h, which was 10 times higher than that obtained in a batch fermentation using free cells and 2.76 times higher than that of an immobilized CSTR. If the nutrient medium fraction was below 0.6 and the pH was below 4.2, the system degenerated. Oxygen also contributed to the system degeneration. Upon degeneration, glucose consumption and solvent yield decreased to 30.9 g/L and 23.0 wt %, respectively. The yield of total liquid product (40.0 wt %) and butanol selectivity (60.0 wt %) remained almost constant. Once the cells were degenerated, they could not be recovered.