The dispersion of Trogoderma granarium in a temperature gradient and comparison with other stored product beetles

The response of stored-product beetles to a temperature gradient was measured with particular emphasis on the initial distribution. When initially introduced at the centre, the following zones were preferred: for Trogoderma granarium 28–33°C (The peak response of females shifts toward the warm side if they are mixed with males, in comparison to the response of female population). Tribolium castaneum 25–34°, Oryzaephilus surinamensis 22–26°, Tenebrio molitor 23–28°, Sitophilus oryzae 20–24°, Callosobruchus maculatus 22–24°, Rhyzopertha dominica 22–28°. T. castaneum and T. molitor aggregated at the corners under isothermal conditions. Some of the species, especially C. maculatus, show hardly any dispersal either in a temperature gradient or under isothermal conditions.

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Zusammenfassung Die Reaktion von vorratsschädlichen Käfern gegenüber einem Temperaturgradienten wurde mit besonderer Berücksichtigung der Ausgangsverteilung gemessen. Bei ursprünglicher Einbringung in das Zentrum wurden folgende Vorzugsbereiche festgestellt; für Trogoderma granarium 28–33°. Der Reaktionsgipfel der Weibchen verschiebt nach der warmen Seite wenn sie mit Männchen gemischt sind, in Vergleichung zu der Responz der weiblichen Population, für Tribolium castaneum 25–34°, für Oryzaephilus surinamensis 22–26°, für Tenebrio molitor 23–28°, für Sitophilus oryzae 20–24°, für Callosobruchus maculatus 22–24° und für Rhyzopertha dominica 22–28°. T. castaneum und T. molitor sammelten sich unter isothermalen Bedingungen in den Ecken. Einige der Arten zeigten weder in einem Temperaturgefälle noch unter isothermalen Bedingungen irgendeine geordnete Verteilung.

     

Kinetic studies on 3-hydroxykynureninase from rat liver

Summary 3-Hydroxykynureninase was purified from rat liver. The Michaelis constants for L-kynurenine and L-3-hydroxykynurenine were determined to be 2.33 × 10^–4 m and 6.85 × 10^–5 m, respectively, at pH 8.41 and 37°. With L-kynurenine as substrate, the enzyme was competitively inhibited by L-alanine, 3-hydroxyanthranilic acid, and several other compounds which contained structural features of either amino acid or aryl portions of the substrate. The effect of pH on the initial velocity, maximal velocity, and Michaelis constant, using L-kynurenine as substrate, was studied. Maximal velocity was strongly pH-dependent, with a maximum at pH 8.4. The Michaelis constant decreased from 11.4 × 10^–4 m at pH 7.1 to 1.30 × 10^–4 m at pH 9.0. Logarithmic plots of these data showed pKa's for functional groups ionizing in the enzyme-substrate complex and free enzyme active center of 7.6 and 8.5, respectively. Possible groups responsible for these ionizations were discussed.Supported in part by a Faculty Creative Endeavor Grant from Central Michigan University, Mount Pleasant, Michigan.     

Purification and characterization of a high molecular mass serine carboxypeptidase from <Emphasis Type="Italic">Monascus pilosus</Emphasis>

Two serine carboxypeptidases, MpiCP-1 and MpiCP-2, were purified to homogeneity from Monascus pilosus IFO 4480. MpiCP-1 is a homodimer with a native molecular mass of 125 kDa composed of two identical subunits of 61 kDa, while MpiCP-2 is a high mass homooligomer with a native molecular mass of 2,263 kDa composed of about 38 identical subunits of 59 kDa. This is unique among carboxypeptidases and distinguishes MpiCP-2 as the largest known carboxypeptidase. The two purified enzymes were both acidic glycoproteins. MpiCP-1 has an isoelectric point of 3.7 and a carbohydrate content of 11%, while for MpiCP-2 these values were 4.0 and 33%, respectively. The optimum pH and temperature were around 4.0 and 50°C for MpiCP-1, and 3.5 and 50°C for MpiCP-2. MpiCP-1 was stable over a broad range of pH between 2.0 and 8.0 at 37°C for 1 h, and up to 55°C for 15 min at pH 6.0, but MpiCP-2 was stable in a narrow range of pH between 5.5 and 6.5, and up to 50°C for 15 min at pH 6.0. Phenylmethylsulfonylfluoride strongly inhibited MpiCP-1 and completely inhibited MpiCP-2, suggesting that they are both serine carboxypeptidases. Of the substrates tested, benzyloxycarbonyl-l-tyrosyl-l-glutamic acid (Z-Tyr-Glu) was the best for both enzymes. The K_m, V_max, K_cat and K_cat/K_m values of MpiCP-1 for Z-Tyr-Glu at pH 4.0 and 37°C were 1.33 mM, 1.49 mM min^–1, 723 s^–1 and 545 mM^–1 s^–1, and those of MpiCP-2 at pH 3.5 and 37°C were 1.55 mM, 1.54 mM min^–1, 2,039 s^–1 and 1,318 mM^–1 s^–1, respectively.     

Fermentation of glycerol to 1,3-propanediol in continuous cultures of Citrobacter freundii

The conversion of glycerol to 1,3-propanediol by Citrobacter freundii DSM 30040 was optimized in single- and two-stage continuous cultures. The productivity of 1,3-propanediol formation was highest under glycerol limitation and increased with the dilution rate (D) to a maximum of 3.7 g·l^–1·h^–1. Glycerol dehydratase seemed to be the rate-limiting step in 1,3-propanediol formation. Conditions for the two-stage fermentation process were as follows: first stage, glycerol limitation (250mM), pH 7.2, D=0.1 h^–, 31° C; second stage, additional glycerol, pH 6.6, D=0.05 h^–1, 28° C. Under these conditions 875mM glycerol were consumed, the final 1,3-propanediol concentration was 545mM, and the overall productivity 1.38 g·1^–1·h^–1. Correspondence to: G. Gottschalk     

Untersuchungen über die Wirkung des hydrostatischen Druckes auf das Wachstum von Delesseria sanguinea (L.) Lamour. aus der westlichen Ostsee

Observations on the effect of hydrostatic pressure on the growth of Delesseria sanguinea (L.) Lamour. from the western Baltic Sea.The post-treatment effects of hydrostatic pressures (100–500 atm) on the growth in lenght and breadth of young prolifications of D. sanguinea were studied at 15°C. Growth activity was compared amongst the prolifications separated from the midrib and not separated ones, and cell-viability as influenced by high pressures was also observed under the microscope. Pressure-temperature relationship was investigated, in which the pressure effects on growth were studied at different temperatures (5°–22°C), using prolifications which were previously adapted to corresponding temperatures. Long-termed experiments were also set up to study the capability of pressure adaptation in young leaflets. In this regard the growth activity was measured after long-termed exposure to relatively smaller pressures (20–60 atm).

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Institut für Meereskunde an der Universität Kiel, B. R. D.

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Meinem hochverehrten Doktorvater, Herrn Prof. Dr. Fritz Gessner, zum ersten Wiederkehr seines Todestages am 20.12.1973 gewidmet.     

Studies on Aspergilli XVI. Effect of pH,temperature, and carbon and nitrogen interaction

Summary The effect of pH, temperature, and carbon and nitrogen interaction on the growth and sporulation ofAspergillus nidulans (Eidam)Wint.,A. rugulosus Thom &Raper,A. variecolor (Berk. &Br.)Thom &Raper andA. quadrilineatus was studied. All the moulds could grow on a wide range of pH (2.0 to 12.0) but the growth was poor on too acid and too alkaline media. Best growth ofA. rugulosus, A. quadrilineatus, andA. violaceus was seen at pH 6.5 and that ofA. nidulans andA. variecolor at pH 7.0. In general maximum production of perithecia was recorded between pH 6.0 and 8.0.All the above species ofAspergillus under study could grow between a temperature range of 10° C–48° C, but the growth was poor at 10° C and 48° C. The present moulds showed good growth at 20° C, 25°C, and 30° C. At 40° CA. nidulans andA. rugulosus showed moderate growth while the rest of the Aspergilli attained good growth. Temperatures between 20° C–30° C favoured excellent perithecial production.In general, little improvement in growth was noted on media containing good carbon and nitrogen sources. Malic acid was found to be useless when supplied singly. But, poor growth was recorded when supplied in combination with amino acids, amide, and peptone. This was due to the fact that these N sources also supplied carbon for their metabolism.     

EEG patterns and body temperatures in man during sleep in arctic winter nights

Two Caucasian males, aged 19 and 22, slept at night in sleeping bags (9.0 clo) in an unheated tent at ambient temperatures between –25 and –35°C in the Arctic. Electroencephalographic (EEG) sleep studies were conducted for two baseline nights (19–21°C), 10 cold exposure nights and 2 recovery nights (19–21°C). Rectal and skin temperatures, and heart rates were also recorded. The subjects suffered disturbances in sleep patterns involving an insomnia composed of an increased wakefulness, a decrease in slow wave sleep and a deprivation in rapid eye movement (REM) sleep. Dissimilarities appeared between the subjects which may be related to differences in thermoregulatory responses.     

Pulmonary diffusing capacity in reptiles (Relations to temperature and O2-uptake)

Summary Pulmonary CO-diffusing capacity (D l _CO), lung volume, pulmonary perfusion and O₂-uptake were measured by non-invasive techniques in the lizardsVaranus exanthematicus andTupinambis teguixin (mean body weight 2.2 kg for both species).The CO-diffusing capacity was at 25–27°C 0.059 mlstpd·kg^–1·min^–1·Torr^–1 inVaranus, which is 47% greater than the value of 0.040 mlstpd·kg^–1·min^–1·Torr^–1 inTupinambis. The lung volume ofVaranus was 36 ml·kg^–1 and that ofTupinambis 20 ml·kg^–1. At 35–37°C the diffusing capacity of lizard lungs are about 25% of those for mammals of comparable size.InVaranus pulmonary CO-diffusing capacity increased with temperature from 0.027 mlstpd·kg^–1·min^–1·Torr^–1 at 17–19 °C to 0.075 mlstpd·kg^–1·min^–1·Torr^–1 at 35–37 °C. This change closely matched a concomitant increase of O₂-uptake. Pulmonary perfusion increased from 27 ml·kg^–1·min^–1 to 55 ml·kg^–1·min^–1 within this temperature range.The study emphasizes that pulmonary diffusing capacity cannot be fully evaluated without information on pulmonary perfusion and O₂-uptake. In reptiles and other ectotherms diffusing capacity must be reported at specified body temperature.     

Multiple temperature optima in collectotrichum graminicola

Summary The dry weights of three isolates ofColletotrichum graminicola (Ces.)Wills., growing at 10°, 15°, 20°, 30°, and 35° C in yeast extract liquid medium were recorded. Two temperature growth optima and minima occurred at 20°C, 30°C and 10°C, 25°C respectively.Portion of a Ph. D. thesis, The Ohio State University, Columbus 10, Ohio, U.S.A. Department of Botany and Plant Pathology. Paper Number 657.     

Ratio of biological and chemical oxidation during the aerobic elimination of sulphide by colourless sulphur bacteria

Summary Culture conditions were evaluated for their relevance to chemical and biological oxidation of sulphide in aqueous solution. With a mixed culture of colourless sulphur bacteria sulphide oxidation was investigated over a concentration range of 0.005 to 3.5 mm S^2–, a pH range from 1.0 to 9.0 and temperatures from 10 to 40° C. Biological sulphide oxidation quickly decreased when fermentation conditions were suboptimal and the proportion of chemical oxidation increased with high pH values and sulphide concentration and increasing temperature. The optimal conditions for biological activity were found to be 3 mm S^2–, pH 7.0, and a mesophilic temperature (40° C).Offprint requests to: C. Plas     

Purification and characterization of a new type of serine carboxypeptidase from<Emphasis Type="Italic"> Monascus purpureus</Emphasis>

Carboxypeptidase produced by Monascus purpureus IFO 4478 was purified to homogeneity. The purified enzyme is a heterodimer with a molecular mass of 132 kDa and consists of two subunits of 64 and 67 kDa. It is an acidic glycoprotein with an isoelectric point of 3.67 and 17.0% carbohydrate content. The optimum pH and temperature were 4.0 and 40 °C, respectively. The enzyme was stable between pH 2.0 and 8.0 at 37 °C for 1 h, and up to 50 °C at pH 5.0 for 15 min. The enzyme was strongly inhibited by piperastatin A, diisopropylfluoride phosphate (DFP), phenylmethylsulfonylfluoride (PMSF), and chymostatin, suggesting that it is a chymotrypsin-like serine carboxypeptidase. Monascus purpureus carboxypeptidase was also strongly inhibited by p-chloromercuribenzoic acid (PCMB) but not by ethylenediaminetetraacetic acid (EDTA) and 1,10-phenanthroline, indicating that it requires cysteine residue but not metal ions for activity. Benzyloxycarbonyl-l-tyrosyl-l-glutamic acid (Z-Tyr-Glu), among the substrates tested, was the best substrate of the enzyme. The K_m, V_max, K_cat, and K_cat/K_m values of the enzyme for Z-Tyr-Glu at pH 4.0 and 37 °C were 0.86 mM, 0.917 mM min^–1, 291 s^–1, and 339 mM^–1 s^–1, respectively.     

Responses of aerial ventilation to hypoxia and hypercapnia inChanna argus,an air-breathing fish

Summary The snake-head fish (Channa argus) is an obligate air-breather inhabiting fresh waters in the temperate zone of East Asia.Ventilation of the air-breathing organ and aerial gas exchange were measured in 1 to 2 kg specimens at 15 and 25°C. Additionally, the ventilatory responses to hypoxia and hypercapnia were studied. Aerial ventilation increased from 1.1 to 2.9 mlbtps·kg^–1·min^–1 when temperature rose from 15 to 25°C. Concomitantly, O₂-uptake through airbreathing increased from 0.1 mlstpd·kg^–1·min^–1 (15°C) to 0.28 mlstpd·kg^–1·min^–1 (25°C), whereas aerial gas exchange was less important for CO₂-climination as evident from low gas exchange ratios (0.16 at 15°C, 0.29 at 25°C).Ventilation increases only slightly in response to inspiration of hypercapnic gas mixtures or to hypoxic conditions in water. By contrast, inspiration of hypoxic gas mixtures caused marked increases of ventilation in particular at the higher temperature.Aerial ventilation inChanna is low compared to values for ectothermic pulmonary breathers. However, its ventilatory responses to hypoxia strikingly resemble those of reptiles: The most marked ventilatory response to hypoxia occurs at the higher temperature where the demands for O₂ are greatest.     

Biological limits of temperature and pressure

Most biologists do not take into account that the greatest portion of today's biosphere is in the realm of environmental extremes, most of it being cold and under pressure. Since bacteria have the ability to adapt to environmental extremes, a close examination for the presence and/or growth of bacteria at high and low temperatures, low temperature and reduced pressure (less than 1 atm), low temperature and increased hydrostatic pressure should be made. It is also within the realm of possibility that life may have arisen in an environmental extreme on the primordial earth and then evolved over time to live under moderate temperatures and 1 atm. Microbial life has been demonstrated at temperatures slightly greater than 90°C, below 0°C, at hydrostatic pressures of 1100 atm, and possibly at cold temperatures in the atmosphere (less than 1 atm). Laboratory experiments have shown that certain enzyme reactions can occur above 100°C under hydrostatic pressure, at –26°C and at 5°C under hydrostatic pressure.Proceedings of the Fourth College Park Colloquium on Chemical Evolution:Limits of Life, University of Maryland, College Park, 18–20 October 1978.     

On the influence of fixations on the normal hydration of rabbit cornea and the total amount of acid mucopolysaccharides in the stroma

Summary The authors studied the influence of fixations on the normal hydration of the rabbit cornea and the total amount of acid mucopolysaccharides (AMPS) in the stroma. The following fixatives were used: formol-calcium chloride at 19° C for 24 hours, formolcetylpyridinium chloride (CPC) at 19 and 28° C for 48 hours, Lillie's fixation at 19° C for 24 hours and Carnoy's fluid at 19° C for 30 minutes. The sections of the corneae were stained with Alcian blue, colloidal Fe³⁺ in the modification according to Rinehart and Abu'l Haj and with toluidine and methylene blue. The amount of AMPS was determined with the method of Rondle and Morgan and the total hydration of the stroma by weighing the corneae before and after using different fixative fluids and by calculation of obtained values on dry weight.The best results were obtained by using formol-CPC at 28° C. At the ordinary room temperature (±19° C) it was the poorest fixation, however, as the corneae in this solution became hydrated. Formol-calcium chloride was the second in the row and it was much better than Lillie's and Carnoy's fluid.The amount of AMPS in the stroma was not essentially changed by the effect of fixatives. Within 24–48 hours formol-CPC at 28° C retained the normal content and formol-calcium chloride caused the 11% decrease of AMPS maximally. The loss of AMPS after other fixatives was minimal.The intensity of staining with cationic dyes in paraffin sections was different after individual fixatives and after the kind of their application and was dependent chiefly on the state of hydration of the corneal stroma: It is impossible to interpret the results of staining reactions in terms of the quantity of AMPS as it was hitherto done.     

Response of chloride efflux from skeletal muscle ofRana pipiens to changes of temperature and membrane potential and diethylpyrocarbonate treatment

Summary Efflux of³⁶Cl^– from frog sartorius muscles equilibrated in two depolarizing solutions was measured. Cl^– efflux consists of a component present at low pH and a pH-dependent component which increases as external pH increases.For temperatures between 0 and 20°C, the measured activation energy is 7.5 kcal/mol for Cl^– efflux at pH 5 and 12.6 kcal/mol for the pH-dependent Cl^– efflux. The pH-dependent Cl^– efflux can be described by the relationu=1/(1+10n(pK _a -pH)), whereu is the Cl^– efflux increment obtained on stepping from pH 5 to the test pH, normalized with respect to the increment obtained on stepping from pH 5 to 8.5 or 9.0. For muscles equilibrated in solutions containing 150mm KCl plus 120mm NaCl (internal potential about –15 mV), the apparent pK _a is 6.5 at both 0 and 20°C, andn=2.5 for 0°C and 1.5 for 20°C. For muscles equilibrated in solutions containing 7.5mm KCl plus 120mm NaCl (internal potential about –65 mV), the apparent pK _a at 0°C is 6.9 andn is 1.5. The voltage dependence of the apparent pK _a suggests that the critical pH-sensitive moiety producing the pH-dependent Cl^– efflux is sensitive to the membrane electric field, while the insensitivity to temperature suggests that the apparent heat of ionization of this moiety is zero. The fact thatn is greater than 1 suggests that cooperativity between pH-sensitive moieties is involved in determining the Cl^– efflux increment on raising external pH.The histidine-modifying reagent diethylpyrocarbonate (DEPC) applied at pH 6 reduces the pH-dependent Cl^– efflux according to the relation, efflux=exp(–k·[DEPC]·t), wheret is the exposure time (min) to DEPC at a prepared initial concentration of [DEPC] (mm). At 17°C,k ^–1=188mm·min. For temperatures between 10 and 23°C,k has an apparent Q₁₀ of 2.5. The Cl^– efflux inhibitor SCN^– at a concentration of 20mm substantially retards the reduction of the pH-dependent Cl^– efflux by DEPC. The findings that the apparent pK _a is 6.5 in depolarized muscles, that DEPC eliminates the pH-dependent Cl^– efflux, and that this action is retarded by SCN^– supports the notion that protonation of histidine groups associated with Cl^– channels is the controlling reaction for the pH-dependent Cl^– efflux.     

Influence de la température sur la consommation d'oxygène de micropterna testacea (Gmel.) (Trichoptera Limnophilidae)

Resume Comme suite aux mesures de consommation d'oxygène faites sur les larves de Polycentropus flavo maculatus Pict., Plectrocnemia conspersa (Curt.) et Limnophilus rhombicus (L.) (Colladdeau 1961), il est étudié dans ce travail, l'influence de la température sur la consommation d'oxygène de Micropterna testacea (Gmel.).La consommation d'oxygène de M. testacea croît avec la température. Cet accroissement est faible entre 3 et 7°C. Dés 10°C jusqu'à 20–25°C, cet accroissement est net et régulier. La variabilité des mesures augmente avec la température. Cette courbe métabolisme-température indique une grande sensibilité aux variations de temperature. Ceci oppose la larve de M. testacea aux larves précedem-ment étudiées qui présentaient une bonne adaptation aux températures situées entre 3 et 20–22°C. Cette différence dans l'allure de la courbe métabolisme-température ne serait pas dûe à des différence de température dans les milieux de vie respectifs des larves, puisqu'elles peuvent se trouver ensemble dans le même ruisseau. Elle serait due au fait que les larves de M. testacea, très rhéophiles dans la nature, deviennent très sensibles aux variations de température quand les expériences sont faites en milieu stagnant.

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Summary As a sequence to the study of oxygen consumption in larvae of Polycentropus flavomaculatus Pict., Plectrocnemia conspersa (Curt.) and Limnophilus rhombicus (L.) (Collardeau 1961) the author investigates the influence of temperature on oxygen consumption by the larva of Micropterna testacea (Gmel.).The oxygen consumption of M. testacea increases with temperature, slowly between 3 and 7°C, more rapidly but still regularly from 10°C to 20–25°C. Variability also increases with temperature. Such a Metabolism-Temperature curve indicates great sensitiveness to temperature variations in M. testacea, as a contrast with the precedingly studied larvae, which could be considered as well adapted to temperature ranging from 3 to 20–22°C. Such differences in Metabolism-Temperature curves are unlikely to be due to different temperature occurring in the animals'habitat, as they may all be found together in the same brook. The very rheophilous M. testacea larva becoming sensitive to temperature changes when studied in stagnant water, might ratber account for the difference.

     

Hypertonic cryohemolysis of human red blood cells

Summary Hypertonic cryohemolysis of human erythrocytes is caused by incubation of the cells in hypertonic medium at a temperature of 20–50°C (stage 1), with subsequent cooling to 0°C (stage 2). In 0.86m sucrose hemolysis increases, with increasing stage 1 temperature, whereas in 1m NaCl cryohemolysis has a temperature optimum at a stage 1 temperature of about 30°C.Cryohemolysis is inhibited by preceding ATP depletion of the cells and bypreincubation of the cells in hypertonic medium at 0°C. In general, anesthetics inhibit cryohemolysis strongly. Only in 1m NaCl at stage 1 temperatures in the range of 40–50°C is cryohemolysis stimulated by these drugs, if present during the entire incubation period. This effect is abolished, however, when the anesthetic is added after piror incubation of the cells at 40–50°C in 1m NaCl.Ghost-bound ANS fluorescence indicates complicated conformation changes in the membrane structure during the various experimental stages leading to cryohemolysis.Some of the experimental results can be considered as examples of molecular hysteresis, thus indicating several different metastable structures of the membrane, under various experimental conditions.The described results support the working hypothesis of Green and Jung that the experimental procedure results in membrane protein damage, preventing normal adaptation of the membrane during cooling.     

The annual reproductive cycle of the freshwater mussel Dreissena polymorpha Pallas in lakes

Summary The annual development of the gonads of Dreissena polymorpha was studied at three sampling sites in two lakes over 3 and 1 1/2 years, respectively. A resting stage occurred after the last spawning in summer/autumn. Oogenesis (accompanied by multiplying segmentation of the oogonia and early growth processes of its oocytes) restarted in specimens at least 1 year old at low temperatures (below 10° C) during winter and early spring. At one location (Fühlinger See) the onset of the spawning season was correlated with an increase of water temperatures above 12° C. At 2 m depth, two main spawning periods in May and August were normally recognized, the first at temperatures of 12–16° C, the second at 16–21° C. It was clearly demonstrated for the first time in Dreissena polymorpha that the oocytes became mature in successive cohorts within one gonad. A female mussel may spawn several times during the reproductive season. At 9 m depth, the onset of spawning also started at about 12° C; this occurred in late summer, with two spawning periods within 1 month at a temperature range of 12–16° C. At another location (Heider Bergsee) the size of the gonads and the oocytes was reduced during April of both years studied, when food supply was low simultaneously with rapidly rising water temperatures in this shallow lake. There was no spawning period during spring. The major spawning period was delayed until July (temperatures 19–22°C). This shows (1) the synchronizing influence of low winter temperatures on the annual reproductive cycle and (2) a temperature threshold of at least 12° C for the start of the spawning processes. The results are discussed with regard to the geographical limits of further spread of Dreissena polymorpha.     

Effect of light intensity on sporulation of Botryosphaeria ribis

Pycnidia were produced by six of seven isolates ofB. ribis at one or more intensity levels of continuous illumination at 21 °C. Under conditions of alternating light (12 h–27 °C) and darkness (12 h–21 °C) pycnidia formed in cultures of six isolates at three or more intensity levels, while one isolate failed to form pycnidia at any intensity level. Pycnidia did not develop when cultures were incubated in complete darkness. Exposure periods as brief as 2 days under continuous illumination at 21 °C induced pycnidial formation. In alternating light (12 h–27 °C) and darkness (12 h–21 °C), the shortest period of exposure which induced pycnidial formation was 4 days. Continuous illumination at 21 °C favored development of uniloculate pycnidia, while alternating light (12 h–27 °C) and darkness (12 h–21 °C) favored formation of multiloculate pycnidia.Contribution No. 22 from The Botany Section of The Department of Biology, The Pennsylvania State University.     

Xylanases of marine fungi of potential use for biobleaching of paper pulp

Microbial xylanases that are thermostable, active at alkaline pH and cellulase-free are generally preferred for biobleaching of paper pulp. We screened obligate and facultative marine fungi for xylanase activity with these desirable traits. Several fungal isolates obtained from marine habitats showed alkaline xylanase activity. The crude enzyme from NIOCC isolate 3 (Aspergillus niger), with high xylanase activity, cellulase-free and unique properties containing 580 U l^–1 xylanase, could bring about bleaching of sugarcane bagasse pulp by a 60 min treatment at 55°C, resulting in a decrease of ten kappa numbers and a 30% reduction in consumption of chlorine during bleaching. The culture filtrate showed peaks of xylanase activity at pH 3.5 and pH 8.5. When assayed at pH 3.5, optimum activity was detected at 50°C, with a second peak of activity at 90°C. When assayed at pH 8.5, optimum activity was seen at 80°C. The crude enzyme was thermostable at 55°C for at least 4 h and retained about 60% activity. Gel filtration of the 50–80% ammonium sulphate-precipitated fraction of the crude culture filtrate separated into two peaks of xylanase with specific activities of 393 and 2,457 U (mg protein)^–1. The two peaks showing xylanase activity had molecular masses of 13 and 18 kDa. Zymogram analysis of xylanase of crude culture filtrate as well as the 50–80% ammonium sulphate-precipitated fraction showed two distinct xylanase activity bands on native PAGE. The crude culture filtrate also showed moderate activities of -xylosidase and -l-arabinofuranosidase, which could act synergistically with xylanase in attacking xylan. This is the first report showing the potential application of crude culture filtrate of a marine fungal isolate possessing thermostable, cellulase-free alkaline xylanase activity in biobleaching of paper pulp.