Production of lipase of Aspergillus foetidus in a batch stirred reactor

Summary Maximum lipase production byAspergillus foetidus was obtained from cultures grown in the medium of 2% olive oil and 0.5% sucrose. The optimal conditions for the production of lipases in the Multigen fermenters were found to be at 500rpm with an airflow of 1.5 liter per mimute. Immobilization of the fungal source was found to be infeasible in natural polymers.     

Photoreceptor-specific efficiencies of β-carotene,zeaxanthin and lutein for photopigment formation deduced from receptor mutant Drosophila melanogaster

Summary Drosophila rearing media had only -carotene, zeaxanthin or lutein as precursors for photopigment chromophores. Zeaxanthin and lutein are potentially optimum sources of the 3-hydroxylated retinoids of visual and accessory photopigments. Mutants made the electroretinogram in white (w) eyes selective for compound eye photoreceptors R1–6, R7 and R8: R1–6 domiantes w's electroretinogram; R7/8 generates w;ora's (ora = outer rhabdomeres absent); R8 generates w sev;- ora's (sev = sevenless). Microspectrophotometry revealed R1-6's visual pigment. In w, all 3 carotenoids yielded monotonic dose-responses for sensitivity (Fig. 4) or visual pigment (Fig. 7). An ultraviolet sensitivity peak from R1-6's sensitizing pigment was present at high but not low doses (Fig. 1). In w;ora, all 3 carotenoids gave similar spectra dominated by R7's high ultraviolet sensitivity (Fig. 2). For w sev;ora, all spectra were the shape expected for R8, peaking around 510 nm (Fig. 3). The sensitivity dose-response was at its ceiling except for low doses in w;ora (Fig. 5) and zero supplementation in w sev;ora (Fig. 6). Hence, without R1-6, most of our dose range mediated maximal visual pigment formation. In Drosophila, -carotene, zeaxanthin and lutein mediate the formation of all major photopigments in R1-6, R7 and R8.Abbreviations ERG electroretinogram - MSP microspectrophotometry - HPLC high pressure liquid chromatography - n.a. numerical aperture - w, sev, ora Drosophila mutants - y, p, r marg types of R7 and R8     

Linear dichroism and orientational studies of carotenoid Langmuir-Blodgett films

The linear dichroism of single monolayers of lutein, zeaxanthin and a mixture of lutein and synthetic phosphatidylcholine has been measured. The angle of orientation of the carotenoid molecules was found to lie between 45° and 51° relative to the plane of the solid support. Although the adsorbed monolayers were mostly in a monomeric state, microscopic observations, as well as the II-A isotherms, indicated the existence of crystalline islets. The results have been interpreted in connection with Haidinger's polarization brushes.     

Effect of different gas environments on bench-scale solid state fermentation of oat straw by white-rot fungi

Three white-rot fungi, Phanerochaete chrysosporium, Polyporus tulipiferae, and Polyporus sp. A336 were grown on 100-g amounts of chopped oat straw in gassed 4.5 L (diameter 16 cm, height 23 cm) solid-state reactors for two weeks. The different gas atmospheres were regulated by (1) air diffusion through foam plugs, (2) intermittent or continuous air flow, (3) intermittent oxygen, 50 or 100% continuous oxygen flow, and (4) continuous 10% carbon dioxide in oxygen flow. The fermented straw was analyzed for total weight loss, Klason lignin loss, and enzymatic (cellulase) hydrolysis. P. chrysosporium grown on straw in continuous oxygen at 35 degrees C caused a 41% weight loss and 33.5% hydrolysis was obtained when the pretreated straw was hydrolyzed with cellulase enzyme. P. tulipiferae caused a 27% weight loss and 34.3% cellulase hydrolysis in the straw at 30 degrees C. Polyporus sp. A336 selectively degraded lignin of the straw and under intermittent oxygen resulted in an 18% weight loss and 33.6% cellulase hydrolysis at 35 degrees C. When the straw was supplemented with 10% xylose (straw basis) and was continuously gassed with 50% oxygen, Polyporus sp. A336 produced a 14.5% weight loss and 38.7% cellulase hydrolysis. Oxygen and carbon dioxide exchange rates were measured for some of these bench-scale fermentations.     

Nippostrongylus brasiliensis: feeding activity in the mouse

Nippostrongylus brasiliensis incorporated the fluorescent dye, Rhodamine B, while feeding in vivo. Uptake of dye in both sexes of helminth increased linearly from 30 to 120 min after the hosts were given dye per os. Feeding by female N. brasiliensis significantly exceeded that of the male at 4 and 5 days postinfection. Feeding declined in older helminths of both sexes. The density of helminths had no effect on their incorporation of dye in vivo. Feeding in male- and female-only groups of worms was similar to that seen in populations of mixed sexes. Feeding by helminths decreased during the first 36 h of food deprivation in the host, but increased during subsequent fasting of the host. Both sexes of N. brasiliensis resumed feeding within 15 min after the fasted hosts were fed. Growth of N. brasiliensis increased linearly from 4 to 7 days postinfection, based on dry weight. Seven-day-old and older females were significantly heavier than males.     

The sporulation-specific penicillin-binding protein 5a from Bacillus subtilis is a DD-carboxypeptidase in vitro

A chemiluminescence method for determining acetylcholinesterase activity is described. It is an adaptation of the chemiluminescence assay of acetylcholine described by Israël & Lesbats [(1981) Neurochem. Int. 3, 81-90; (1981) J. Neurochem. 37, 1475-1483]. The acetylcholinesterase activity is measured by monitoring the increase in light emission produced by the accumulation of choline or by determining the amount of choline generated after a short interval. The assay is rapid and sensitive, and uses the natural substrate of the enzyme. Kinetic data obtained with this procedure for acetylcholinesterase from Torpedo and Electrophorus electric organs were comparable with those obtained by using the method of Ellman, Courtney, Andres & Featherstone [(1961) Biochem. Pharmacol. 7, 88-95]. In addition, it was shown that sodium deoxycholate totally inactivated Torpedo acetylcholinesterase but not the Electrophorus enzyme. Competitive inhibitors of acetylcholinesterase protected the enzyme from inactivation.     

Epithelial action potentials inOikopleura (Tunicata: Larvacea)

Summary The passive electrical properties and initiation of action potentials have been examined in the external epithelium of oikopleurid larvacean tunicates. The epithelial cells are electrically coupled, and are polygons up to 200 m across and up to 1.4–2.8 m thick. Membrane constants determined by a 2-electrode study were forO. dioica:: 922 m; R_m: 4.3 kcm₂; R_i: 82.7 cm. Corresponding values for the largerO. longicauda were: 3350 m; 35.6 kcm²; and 104.5 cm. Mean resting potentials in both species were around 80 mV. Mechanical stimulation evokes over-shooting action potentials propagated (at 18 °C) at some 40 cm/s. These are rapid events, repolarisation being almost complete in 5 ms. There is no undershoot.When the recording electrode penetrates the epithelial cell from its inner surface distant mechanical stimulation may evoke similar action potentials arising from the stimulus site, but more often evokes graded small depolarisations which give rise to action potentials with increasing strength of mechanical stimulation. Reasons are given for considering these to be generator potentials resulting from deformation of the outer epithelial cell membrane by the tip of the recording electrode. The effects of epithelial action potentials upon the potentials recorded from the caudal muscle cells are briefly described.