Differential expression of thermophilic phosphatases in the wild type and auxotrophic mutant strains of <Emphasis Type="Italic">Thermoactinomyces vulgaris</Emphasis>

In the wild type strain (stock no. 1227) of Thermoactinomyces vulgaris, as reported earlier [Sinha and Singh (1980) Biochem. J. 190, 457–460], all phosphatase isoenzymes (three alkaline — AlpI, AlpII and AlpIII, and one acidic — Acp) are present. However, the auxotrophic mutants, the strains 1286 (thi ⁻), 1279 (nic ⁻, ura ⁻) and 1278 (thi ⁻, ura ⁻) exhibited two alkaline phosphatase isoenzymes (AlpII and AlpIII), but AlpI was lacking. In the strain 1261 (nic ⁻, thi ⁻), only AlpIII was expressed, and AlpI and AlpII isoenzymes were missing. The results suggest that the strains, which require either thiamine (1286 and 1278) or nicotinamide (1279) for their growth, were AlpI ⁻ mutants; and the strain (1261), which requires both thiamine and nicotinamide for its growth, was AlpI ⁻/AlpII ⁻ double mutant. There was no direct correlation between uracil auxotrophy and the expression of phosphatases. The uniform expression of AlpIII and Acp in all the strains, irrespective of their nutrient requirements, suggest that these constitutive phosphatases are species-specific. The specific activities of the thermophilic acid and alkaline phosphatases were maximum in the wild type strain (1227) of T. vulgaris. The next in phosphatase activity was the strain 1279 (an AlpI ⁻ mutant), followed by their decrease, in order, in the strains 1286 and 1278 (which were also AlpI ⁻ mutants); while least activity of these enzymes was observed in the obligate thermophile strain 1261 (AlpI ⁻/AlpII ⁻ double mutant).     

The production of xylitol from d-xylose by fermentation with Hansenula polymorpha

We have analysed the influence of the initial pH of the medium and the quantity of aeration provided during the batch fermentation of solutions of d-xylose by the yeast Hansenula polymorpha (34438 ATCC). The initial pH was altered between 3.5 and 6.5 whilst aeration varied between 0.0 and 0.3 vvm. The temperature was kept at 30 °C during all the experiments. Hansenula polymorpha is known to produce high quantities of xylitol and low quantities of ethanol. The most favourable conditions for the growth of xylitol turned out to be: an initial pH of between 4.5 and 5.5 and the aeration provided by the stirring vortex alone. Thus, at an initial pH of 5.5, the maximum specific production rate (μ_m) was 0.41 h⁻¹, the overall biomass yield (Y _x/s ^G) was 0.12 g g⁻¹, the specific d-xylose-consumption rate (q _s ) was 0.075 g g⁻¹ h⁻¹ (for t = 75 h), the specific xylitol-production rate (q _Xy ) was 0.31 g g⁻¹ h⁻¹ (for t = 30 h) and the overall yields of ethanol (Y _E/s ^G) and xylitol (Y _Xy/s ^G) were 0.017 and 0.61 g g⁻¹ respectively. Both q _s and q _Xy decreased during the course of the experiments once the exponential growth phase had finished. Received: 26 March 1998 / Received revision: 30 June 1998 / Accepted: 2 July 1998     

Energetics of swimming at maximal speeds in humans

The energy cost per unit of distance (C _s, kilojoules per metre) of the front-crawl, back, breast and butterfly strokes was assessed in 20 elite swimmers. At sub-maximal speeds (v), C _s was measured dividing steady-state oxygen consumption (V˙O₂) by the speed (v, metres per second). At supra-maximal v, C _s was calculated by dividing the total metabolic energy (E, kilojoules) spent in covering 45.7, 91.4 and 182.9 m by the distance. E was obtained as: E = E _an+V˙O_2max t _p−V˙O_2max(1−e^{−( t p/)}), where E _an was the amount of energy (kilojoules) derived from anaerobic sources, V˙O_2max litres per second was the maximal oxygen uptake, α (=20.9 kJ · l O₂ ⁻¹) was the energy equivalent of O₂, τ (24 s) was the time constant assumed for the attainment of V˙O_2max at muscle level at the onset of exercise, and t _p (seconds) was the performance time. The lactic acid component was assumed to increase exponentially with t _p to an asymptotic value of 0.418 kJ · kg⁻¹ of body mass for t _p ≥ 120 s. The lactic acid component of E _an was obtained from the net increase of lactate concentration after exercise (Δ[La]_b) assuming that, when Δ[La]_b = 1 mmol · l⁻¹ the net amount of metabolic energy released by lactate formation was 0.069 kJ · kg⁻¹. Over the entire range of v, front crawl was the least costly stroke. For example at 1 m · s⁻¹, C _s amounted, on average, to 0.70, 0.84, 0.82 and 0.124 kJ · m⁻¹ in front crawl, backstroke, butterfly and breaststroke, respectively; at 1.5 m · s⁻¹, C _s was 1.23, 1.47, 1.55 and 1.87 kJ · m⁻¹ in the four strokes, respectively. The C _s was a continuous function of the speed in all of the four strokes. It increased exponentially in crawl and backstroke, whereas in butterfly C _s attained a minimum at the two lowest v to increase exponentially at higher v. The C _s in breaststroke was a linear function of the v, probably because of the considerable amount of energy spent in this stroke for accelerating the body during the pushing phase so as to compensate for the loss of v occurring in the non-propulsive phase. Accepted: 14 April 1998     

Antimicrobial activity of an endophytic <Emphasis Type="Italic">Xylaria</Emphasis> sp.YX-28 and identification of its antimicrobial compound 7-amino-4-methylcoumarin

An endophytic Xylaria sp., having broad antimicrobial activity, was isolated and characterized from Ginkgo biloba L. From the culture extracts of this fungus, a bioactive compound P3 was isolated by bioactivity-guided fractionation and identified as 7-amino-4-methylcoumarin by nuclear magnetic resonance, infrared, and mass spectrometry spectral data. The compound showed strong antibacterial and antifungal activities in vitro against Staphylococcus aureus [minimal inhibitory concentrations (MIC) 16 μg·ml⁻¹], Escherichia coli (MIC, 10 μg·ml⁻¹), Salmonella typhia (MIC, 20 μg·ml⁻¹), Salmonella typhimurium (MIC, 15 μg·ml⁻¹), Salmonella enteritidis (MIC, 8.5 μg·ml⁻¹), Aeromonas hydrophila (MIC, 4 μg·ml⁻¹), Yersinia sp. (MIC, 12.5 μg·ml⁻¹), Vibrio anguillarum (MIC, 25 μg·ml⁻¹), Shigella sp. (MIC, 6.3 μg·ml⁻¹), Vibrio parahaemolyticus (MIC, 12.5 μg·ml⁻¹), Candida albicans (MIC, 15 μg·ml⁻¹), Penicillium expansum (MIC, 40 μg·ml⁻¹), and Aspergillus niger (MIC, 25 μg·ml⁻¹). This is the first report of 7-amino-4-methylcoumarin in fungus and of the antimicrobial activity of this metabolite. The obtained results provide promising baseline information for the potential use of this unusual endophytic fungus and its components in the control of food spoilage and food-borne diseases.     

Efficient induction of formate hydrogen lyase of aerobically grown <Emphasis Type="Italic">Escherichia coli</Emphasis> in a three-step biohydrogen production process

A three-step biohydrogen production process characterized by efficient anaerobic induction of the formate hydrogen lyase (FHL) of aerobically grown Escherichia coli was established. Using E. coli strain SR13 (fhlA ⁺⁺, ΔhycA) at a cell density of 8.2 g/l medium in this process, a specific hydrogen productivity (28.0 ± 5.0 mmol h⁻¹ g⁻¹ dry cell) of one order of magnitude lower than we previously reported was realized after 8 h of anaerobic incubation. The reduced productivity was attributed partly to the inhibitory effects of accumulated metabolites on FHL induction. To avoid this inhibition, strain SR14 (SR13 ΔldhA ΔfrdBC) was constructed and used to the effect that specific hydrogen productivity increased 1.3-fold to 37.4 ± 6.9 mmol h⁻¹ g⁻¹. Furthermore, a maximum hydrogen production rate of 144.2 mmol h⁻¹ g⁻¹ was realized when a metabolite excretion system that achieved a dilution rate of 2.0 h⁻¹ was implemented. These results demonstrate that by avoiding anaerobic cultivation altogether, more economical harvesting of hydrogen-producing cells for use in our biohydrogen process was made possible.     

Enhanced Solubility,Stability, and Transcorneal Permeability of Delta-8-Tetrahydrocannabinol in the Presence of Cyclodextrins

The purpose of this study was to investigate the effect of cyclodextrins (CDs) on aqueous solubility, stability, and in vitro corneal permeability of delta-8-tetrahydrocannabinol (Δ⁸-THC). Phase solubility of Δ⁸-THC was studied in the presence of 2-hydroxypropyl-β-cyclodextrin (HPβCD), randomly methylated-β-cyclodextrin (RMβCD) and sulfobutyl ether-β-cyclodextrin sodium salt (SβCD). Stability of Δ⁸-THC in 5% w/v aqueous CD solutions, as a function of pH, was studied following standard protocols. In vitro corneal permeation of Δ⁸-THC (with and without CDs) across excised rabbit cornea was also determined. Phase-solubility profile of Δ⁸-THC in the presence of both HPβCD and RMβCD was of the A_P type, whereas, with SβCD an A_L type was apparent. Aqueous solubility of Δ⁸-THC increased to 1.65, 2.4, and 0.64 mg/mL in the presence of 25% w/v HPβCD, RMβCD, and SβCD, respectively. Significant degradation of Δ⁸-THC was not observed within the study period at the pH values studied, except for at pH 1.2. Transcorneal permeation of Δ⁸-THC was dramatically improved in the presence of CDs. The results demonstrate that CDs significantly increase aqueous solubility, stability, and transcorneal permeation of Δ⁸-THC. Thus, topical ophthalmic formulations containing Δ⁸-THC and modified beta CDs may show markedly improved ocular bioavailability.     

Critical Levels of Selenium in Different Crops Grown in an Alkaline Silty Loam Soil Treated with Selenite-Se

Critical levels of selenium in raya (Brassica juncea Czern L.), maize (Zea mays L.), wheat (Triticum aestivum L.) and rice (Oryza sativa L.) were worked out by growing these crops in an alkaline silty loam soil treated with different levels of selenite-Se ranging from 1 to 25 μg g⁻¹ soil. Significant decrease in dry matter yield was observed above a level of 5 μg Se g⁻¹ soil in raya and maize; 4 μg Se g⁻¹ soil in wheat and 10 μg Se g⁻¹ soil in rice shoots. The critical level of Se in plants above which significant decrease in yield would occur was found to be 104.8 μg g⁻¹ in raya, 76.9 μg g⁻¹ in maize, 41.5 μg g⁻¹ in rice and 18.9 μg g⁻¹ in wheat shoots. Significant coefficients of correlation were observed between Se content above the critical level and dry matter yield of raya as well as rice (r = −0.99, P ≤ 0.01), wheat (r = −0.97, P ≤ 0.01) and maize ((r = −0.96, P ≤ 0.01). A synergistic relationship was observed between S and Se content of raya (r = 0.96, P ≤ 0.01), wheat (r = 0.89, P ≤ 0.01), rice (r = 0.85, P ≤ 0.01) and maize (r = 0.84, P ≤ 0.01). Raya, maize and rice absorbed Se in levels toxic for animal consumption (i.e. > 5 mg Se kg⁻¹) when the soil was treated with more than 1.5 μg Se g⁻¹. In case of wheat, application of Se more than 3 μg g⁻¹ soil resulted in production of toxic plants.     

Effects of cortisol and fluoride on ion-transporting ATPase activities in cultured osteoblastlike cells

Summary Na⁺,K⁺-ATPase, HCO ₃ ⁻ -ATPase, Ca²⁺,Mg²⁺,-ATPase, Ca²⁺-ATPase, and alkaline phosphatase activities were measured in cultures of osteoblastlike cells treated with fluoride and cortisol separately and in combinations. Low concentrations of cortisol increased HCO ₃ ⁻ -ATPase (10⁻¹¹ to 10⁻¹⁸ M cortisol) and alkaline phosphatase (10⁻¹¹ to 10⁻⁹ M cortisol) activities, but higher cortisol concentrations reduced these activities. Na⁺,K⁺-ATPase, Ca²⁺,Mg²⁺-ATPase, and Ca²⁺-ATPase activities tended only to be reduced by cortisol. Fluoride (10⁻⁶ and 5×10⁻⁶ M) increased HCO ₃ ⁻ -ATPase and alkaline phosphatase activities, but these activities were similar to controls in the presence of 10⁻⁵ M fluoride. Ca²⁺,Mg²⁺-ATPase activity was decreased and Na⁺,K⁺-ATPase activity was increased as the concentration of fluoride increased (10⁻⁶ to 10⁻⁵ M). Preliminary experiments with fluoride indicated that lower concentrations (10⁻⁷ M) were without effect. Cortisol concentrations of 10⁻⁹ and 10⁻⁸ M were chosen for studies with combinations of cortisol and fluoride because the effects of these concentrations on alkaline phosphatase activity were opposite, i.e. 10⁻⁹ M increased whereas 10⁻⁸ M decreased activity. Fluoride concentrations of 10⁻⁶, 5×10⁻⁶, and 10⁻⁵ M were chosen because a peak of alkaline phosphatase activity occurred at 5×10⁻⁶ M fluoride. Higher (10⁻⁴ M) and lower (10⁻⁷ M) fluoride concentrations were without effect. The effects of combinations of cortisol and fluoride depend on the enzyme activity measured. Fluoride (10⁻⁶ M) combined with cortisol (10⁻⁹ M) produced a peak of Na⁺,K⁺-ATPase activity. The increased activity obtained with all concentrations of fluoride alone was preserved when fluoride was combined with 10⁻⁸ M cortisol, although the activity tended to be reduced at 5×10⁻⁶ and 10⁻⁵ M fluoride. HCO ₃ ⁻ -ATPase activity was increased by fluoride combined with 10⁻⁸ M cortisol and decreased by fluoride combined with 10⁻⁹ M cortisol compared to the activities obtained with fluoride alone. The decrease in Ca²⁺,Mg²⁺-ATPase activity caused by fluoride alone was prevented by 10⁻⁹ and enhanced by 10⁻⁸ M cortisol, although all treatments produced the same activity at 10⁻⁵ M fluoride. Ca²⁺-ATPase activity tended to be increased by combinations of fluoride and cortisol, but significantly so only at 10⁻⁵ M fluoride in combinations with 10⁻⁸ and 10⁻⁹ M cortisol. Alkaline phosphatase activity was increased by fluoride combined with 10⁻⁹ M cortisol and decreased by fluoride combined with 10⁻⁸ M cortisol compared to the activities obtained with fluoride alone. These results suggest that the abilities of bone cells to regulate ion transport (as reflected in their ion-transporting ATPase activities) are modulated by glucocorticoids and fluoride. Inasmuch as these cells may regulate the ionic composition and concentrations of the bone extracellular fluid (ECF) in vivo, the modulation of their activities by cortisol and fluoride may result in altered bone ECF composition. This work was supported by Grant NAG-2-108 from the National Aeronautics and Space Administration, D.C., and Grant PO1 NS15767 from the National Institute of Neurological and Communicative Disorders and Stroke, Bethesda, MD.     

Flow-Dependent Activation of Maxi K+ Channels in Apical Membrane of Rabbit Connecting Tubule

The Ca²⁺-activated maxi K⁺ channel was found in the apical membrane of everted rabbit connecting tubule (CNT) with a patch-clamp technique. The mean number of open channels (NP _o ) was markedly increased from 0.007 ± 0.004 to 0.189 ± 0.039 (n= 7) by stretching the patch membrane in a cell-attached configuration. This activation was suggested to be coupled with the stretch-activation of Ca²⁺-permeable cation channels, because the maxi K⁺ channel was not stretch-activated in both the cell-attached configuration using Ca²⁺-free pipette and in the inside-out one in the presence of 10 mm EGTA in the cytoplasmic side. The maxi K⁺ channel was completely blocked by extracellular 1 μm charybdotoxin (CTX), but was not by cytoplasmic 33 μm arachidonic acid (AA). On the other hand, the low-conductance K⁺ channel, which was also found in the same membrane, was completely inhibited by 11 μm AA, but not by 1 μm CTX. The apical K⁺ conductance in the CNT was estimated by the deflection of transepithelial voltage (ΔV _t ) when luminal K⁺ concentration was increased from 5 to 15 mEq. When the tubule was perfused with hydraulic pressure of 0.5 KPa, the ΔV _t was only −0.7 ± 0.4 mV. However, an increase in luminal fluid flow by increasing perfusion pressure to 1.5 KPa markedly enhanced ΔV _t to −9.4 ± 0.9 mV. Luminal application of 1 μm CTX reduced the ΔV _t to −1.3 ± 0.6 mV significantly in 6 tubules, whereas no significant change of ΔV _t was recorded by applying 33 μm AA into the lumen of 5 tubules (ΔV _t =−7.2 ± 0.5 mV in control vs.ΔV _t =−6.7 ± 0.6 mV in AA). These results suggest that the Ca²⁺-activated maxi K⁺ channel is responsible for flow-dependent K⁺ secretion by coupling with the stretch-activated Ca²⁺-permeable cation channel in the rabbit CNT. Received: 21 August 1997/Revised: 20 March 1998     

Cyanide Inhibition of Chloride Conductance Across Toad Skin

The effect of cyanide (CN⁻) on voltage-activated or cAMP-induced passive chloride conductance (G ^Cl ) was analyzed in isolated toad skin. Comparatively low concentrations of CN⁻ inhibited G ^Cl almost completely and fully reversibly, regardless of whether it was applied from the mucosal or serosal side. The IC₅₀ was 180 ± 12 μm for voltage-activated G ^Cl and 305 ± 30 μm for the cAMP-inducted conductance. At [CN] <100 μm, the initial inhibition frequently declined partly in the continuous presence of CN⁻. Inhibition was independent of the presence of Ca²⁺. Inhibition was stronger at more alkaline pH, which suggests that dissociated CN⁻ is the effective inhibitor. The onset of the inhibition of voltage-activated or cAMP-induced G ^Cl by CN⁻ occurred with half-times of 34 ± 10 sec, whereas reversibility upon washout was twice as fast (18 ± 7 sec). If [CN⁻] <200 μm was applied under inactivating conditions (serosa −30 mV), the reduction of G ^Cl was stronger upon subsequent voltage-activation than under steady-state activated conditions. This effect was essentially complete less than 30 sec after apical addition of CN⁻, but G _t recovered thereafter partially in the continuous presence of CN⁻. Dinitrophenol inhibited G ^Cl similarly, while omission of oxygen did not affect it. These observations, as well as the time course of inhibition and the full reversibility, suggest that interference of CN⁻ with oxidative phosphorylation and subsequent metabolic depletion is not the reason for the inhibition of G ^Cl . We propose that the inhibition is directly on G ^Cl , presumably by competition with Cl⁻ at a rate-limiting site in the pathway. Location and molecular nature of this site remain to be identified. Received: 8 February 1999/Revised: 22 September 1999     

Ethene as an auxiliary substrate for the cooxidation of cis-1,2-dichloroethene and vinyl chloride

Cultures able to dechlorinate cis-1,2-dichloroethene (cDCE) were selected with ethene (3–20%, v/v) as the sole source of carbon and energy. One mixed culture (K20) could degrade cDCE (400 μmol l^–1) or vinyl chloride (100 μmol l^–1) in the presence of ethene (≤ 80 μmol l^–1 and ≤ 210 μmol l^–1, respectively). This culture consists of at least five bacterial strains. All five strains were able to degrade cDCE cometabolically in pure culture. The mixed culture K20 was highly tolerant against cDCE (up to 6 mmol l^–1 in the liquid phase). Degradation of cDCE (200 μmol l^–1) was not affected by the presence of trichloroethene (100 μmol l^–1) or tetrachloroethene (100 μmol l^–1). Transformation yields (T_y, defined as unit mass of chloroethene degraded per unit mass of ethene consumed) of the mixed culture K20 were relatively high (0.51 and 0.61 for cDCE and vinyl chloride, respectively). The yield for cDCE with ethene as auxiliary substrate was ninefold higher than any values reported with methane or methane/formate as auxiliary substrate. The viability of the cells of the mixed culture K20 (0.3 mg of cells ml^–1) was unaffected by the transformation of ≤ 200 μmol l^–1 cDCE in 300 min. Received: 9 March 1999 / Accepted: 21 July 1999     

Effects of temperature and ammonium on growth,pigment production and nitrogen uptake by four species of <Emphasis Type="BoldItalic">Porphyra</Emphasis> (Bangiales,Rhodophyta) native to the New England coast

Porphyra is one of the world’s most valued maricultured seaweeds and has been cultivated for several hundred years in Asia. The objective of this study was to produce critical information as a guide for the selection of an appropriate Porphyra species from coastal New England for the development of a land-based aquaculture system. Four Northwest Atlantic Porphyra species: P. leucosticta, P. amplissima, P. linearis and P. umbilicalis, were cultivated for 1 and 2 weeks at saturated light intensities (100–150 μmol photons m⁻²s⁻¹) and six combinations of ammonium (25 and 250 μmoles L⁻¹) and temperature (10, 15 and 20°C). Specific growth rate (SGR) increased with decreasing temperature in P. leucosticta, P. linearis and P. umbilicalis and increased with increasing temperature in P. amplissima. The SGR of all species was greater at the higher ammonium concentration. Porphyra linearis had the highest SGR, increasing in biomass by approximately 16% day⁻¹. Phycoerythrin (PE) content was higher at 10°C and 250 μmoles L⁻¹ in all species except P. amplissima. The PE content, measured as fresh weight (FW), of P. linearis (29 mg g⁻¹ FW⁻¹) and P. umbilicalis (26 mg g⁻¹ FW⁻¹) was significantly higher than the other two species. Tissue nitrogen content of all species measured in dry weight was on average 1.45% higher at 250 μmoles L⁻¹ than at 25 μmoles L⁻¹ ammonium concentration. Porphyra umbilicalis had the highest tissue nitrogen contents (6.76%) at 10°C and 250 μmoles L⁻¹ ammonium. Based on these results, P. linearis and P. umbilicalis should be considered as potential candidates for bioremediation with finfish and shellfish mariculture.     

Effects of manganese on the growth,photosystem II and SOD activity of the dinoflagellate <Emphasis Type="Italic">Amphidinium</Emphasis> sp.

Experimental ecology methods and chlorophyll fluorescence technology were used to study the effects of different concentrations of manganese (10⁻¹²– 10⁻⁴ mol L⁻¹) on the growth, photosystem II and superoxide dismutase (SOD) activity of Amphidinium sp. MACC/D31. The results showed that manganese had a significant effect on the growth rate, fluorescence parameters (maximal photochemical efficiency of PSII (F _v /F _m ), photochemical quenching (qP) and non-photochemical quenching (NPQ)) in the exponential stage (days 1–3) and SOD activity of Amphidinium sp. (P < 0.05). F _v/F _m in the exponential stage in 10⁻¹² mol L⁻¹ manganese concentration was significantly lower whilst qP and NPQ significantly higher than those in the other concentrations. F _v /F _m (days 6–9) in 10⁻⁴ mol L⁻¹ manganese was significantly higher than those in the other concentrations. F _v /F _m (days 3–6) increased with increased concentration of manganese from 10⁻¹² to 10⁻⁴ mol L⁻¹. The values of qP and NPQ decreased with decreased concentrations of manganese, except for those in days 4–6. F _v /F _m under each concentration increased earlier and decreased later with culture stage whilst NPQ decreased earlier and increased later. The SOD activity increased with increased concentration of manganese from 10⁻¹² to 10⁻⁸ mol L⁻¹. The SOD activity in 10⁻⁴ mol L⁻¹ manganese was significantly higher than those in the other concentrations and in 10⁻¹² mol L⁻¹ manganese, it was significantly lower than those in the other concentrations.     

Effects of salinity on cell growth and docosahexaenoic acid content of the heterotrophic marine microalga Crypthecodinium cohnii

The effects of salinity on cell growth and docosahexaenoic acid (DHA) content of three marine microalgal strains, Crythecodinium cohnii ATCC 30556, C. cohnii ATCC 50051 and C. cohnii RJH were investigated. The lag phases of the three strains increased with increasing salinity in Porphyridium medium. The specific growth rate of C. cohnii ATCC 30556 was the highest at 9 g L⁻¹ NaCl while the other two strains had their highest specific growth rates at 5 g L⁻¹ NaCl. The highest cell dry weight concentrations of 2.51 g L⁻¹ and 1.56 g L⁻¹ were achieved at 9 g L⁻¹ NaCl for C. cohnii ATCC 30556 and ATCC 50051, respectively, while the highest dry weight concentration of 2.49 g L⁻¹ was achieved at 5 g L⁻¹ NaCl for C. cohnii RJH. The highest cell growth yield coefficient on glucose was 0.5 g g⁻¹ for both C. cohnii ATCC 30556 and C. cohnii RJH and 0.45 g g⁻¹ for C. cohnii ATCC 50051. All three strains responded to the change of salinity by modifying their cellular fatty acid compositions. At 9 g L⁻¹ NaCl, C. cohnii ATCC 30556 had the highest total fatty acid content and DHA (C22:6) proportion. In contrast, C. cohnii ATCC 50051 and C. cohnii RJH had the highest DHA content at 5 g L⁻¹ NaCl. C. cohnii ATCC 30556 and ATCC 50051 had the highest DHA yield (131.55 and 68.24 mg L⁻¹ respectively) at 9 g L⁻¹ NaCl while C. cohnii RJH had the highest DHA yield (128.83 mg L⁻¹) at 5 g L⁻¹ NaCl. Received 27 May 1999/ Accepted in revised form 27 August 1999     

Soy molasses as fermentation substrate for production of butanol using Clostridium beijerinckii BA101

Spray-dried soy molasses (SDSM) contains the sugars dextrose, sucrose, fructose, pinitol, raffinose, verbascose, melibiose, and stachyose. Of the 746 g kg⁻¹ total sugars in SDSM, 434 g kg⁻¹ is fermentable using Clostridium beijerinckii BA101. SDSM was used to produce acetone, butanol, and ethanol (ABE) by C. beijerinckii BA101 in batch cultures. Using 80 g l⁻¹ SDSM, 10.7 g l⁻¹ ABE was produced in P2 medium. Higher concentrations of SDSM resulted in poor solvent production due to the presence of excessive salt and inhibitory components. C. beijerinckii BA101 in SDSM at 80 g l⁻¹ concentration produced 22.8 g l⁻¹ ABE when supplemented with 25.3 g l⁻¹ glucose. SDSM contains 57.4 g kg⁻¹ mineral ash and 2% tri-calcium phosphate. Tri-calcium phosphate up to 43.1 g l⁻¹ was not inhibitory and at a tri-calcium phosphate concentration of 28.8 g l⁻¹, the culture produced more solvents (30.1 g l⁻¹) than the control experiment (23.8 g l⁻¹). In contrast, sodium chloride was a strong inhibitor of C. beijerinckii BA101 cell growth. At a concentration of 10 g l⁻¹ sodium chloride, a maximum cell concentration of 0.6 g l⁻¹ was achieved compared to 1.7 g l⁻¹ in the control experiment. The effects of two salts on specific growth rate constant (μ) and specific rate of ABE production (ν) for C. beijerinckii BA101 were examined. Journal of Industrial Microbiology & Biotechnology (2001) 26, 290–295. Received 20 September 2000/ Accepted in revised form 16 February 2001     

Biosorption of organochlorine pesticides using fungal biomass

Cladosporium strain AJR³18,501 was tested for its ability to sorb the organochlorine pesticide (OCP) p,p′-DDT from aqueous media. When p,p′-DDT was added to distilled water, ethanol or 1-propanol solutions in excess of its solubility, p,p′-DDT was sorbed onto the fungal biomass. Increasing the amount of p,p′-DDT in solution by changing the medium composition increased sorbent uptake: p,p′-DDT uptake by the fungal biomass was 2.5 times greater in 25% 1-propanol (17 mg of p,p′-DDT g⁻¹ dry weight fungal biomass) than in distilled water. When p,p′-DDT was dissolved in 25% 1-propanol (12 mg l⁻¹), rapid p,p′-DDT sorption occurred during the first 60 min of incubation. p,p′-DDT in solution was reduced to 2.5 mg l⁻¹ with the remaining p,p′-DDT recovered from the fungal biomass. A number of environmental parameters were tested to determine their effect on p,p′-DDT biosorption. As arsenic (As) is prevalent at DDT-contaminated cattle dip sites, its effect on p,p′-DDT uptake was determined. The presence of As [As(III) or As(V) up to 50 mg l⁻¹] did not inhibit p,p′-DDT uptake and neither As species could be sorbed by the fungal biomass. Changing the pH of the medium from pH 3 to 10 had a small effect on p,p′-DDT sorption at low pH indicating that an ion exchange process is not the major mechanism for p,p′-DDT sorption. Other mechanisms such as Van der Waals forces, chemical binding, hydrogen bonding or ligand exchange may be involved in p,p′-DDT uptake by Cladosporium strain AJR³18,501. Journal of Industrial Microbiology & Biotechnology (2002) 29, 163–169 doi:10.1038/sj.jim.7000280 Received 15 January 2002/ Accepted in revised form 18 May 2002     

Growth and physiological changes in saplings of Minquartia guianensis and Swietenia macrophylla during acclimation to full sunlight

Low light availability under a forest canopy often limits plant growth; however, sudden increase in light intensity may induce photoinhibition of photosynthesis. The aim of this study was to evaluate the ecophysiological changes that occur in potted plants of Minquartia guianensis and Swietenia macrophylla during the acclimation process to full sunlight. We used six full-sun independent acclimation periods (30, 60, 90, 120, 150, and 180 days) and a control kept in the shade. Shading was obtained by placing plants under the canopy of a small forest. The F_v/F_m ratio, net photosynthetic rate (P _N), the maximum carboxylation velocity of Rubisco (V _cmax), maximum electron transport rate (J _max), specific leaf area (SLA), and growth were assessed at the end of each of the six acclimation periods. Plant exposure to full sunlight caused a sudden decrease in the F_v/F_m ratio (photoinhibition) particularly in Minquartia. Photooxidation (necrotic patches) of the leaf tissue was observed in upper leaves of Minquartia. The higher P _N values were observed in Swietenia under full sun, about 12 μmol(CO₂) m⁻² s⁻¹. V _cmax25 values were higher after 90 days of acclimation, about 14 μmol(CO₂) m⁻² s⁻¹ for Minquartia, and 35 μmol(CO₂) m⁻² s⁻¹ for Swietenia. At the end of a 180-d acclimation period J _max25 was 35 μmol(electron) m⁻² s⁻¹ for Minquartia and 60 μmol(electron) m⁻² s⁻¹ for Swietenia. SLA was higher in Swietenia than in Minquartia. In Minquartia, monthly rate of leaf production per plant (MRLP) was positive (0.22 leaf month⁻¹) after four months in the open. Whereas, in Swietenia MRLP was positive (0.56 leaf month⁻¹) after an acclimation period of two months. After six months in the open, height growth rates were 3.5 and 28 mm month⁻¹ for Minquartia and Swietenia, respectively. The greater acclimation capacity of Swietenia was associated to an enhanced photosynthetic plasticity under full sun. In Minquartia, transition to full-sun conditions and lack of physiological adjustment resulted in severe photoinhibition and loss of leaves.     

Transpiration and whole-tree conductance in ponderosa pine trees of different heights

Changes in leaf physiology with tree age and size could alter forest growth, water yield, and carbon fluxes. We measured tree water flux (Q) for 14 ponderosa pine trees in two size classes (12 m tall and ∼40 years old, and 36 m tall and ∼ 290 years old) to determine if transpiration (E) and whole-tree conductance (g _t) differed between the two sizes of trees. For both size classes, E was approximately equal to Q measured 2 m above the ground: Q was most highly correlated with current, not lagged, water vapor pressure deficit, and night Q was <12% of total daily flux. E for days 165–195 and 240–260 averaged 0.97 mmol m^–2 (leaf area, projected) s^–1 for the 12-m trees and 0.57 mmol m^–2 (leaf area) s^–1 for the 36-m trees. When photosynthetically active radiation (I _P) exceeded the light saturation for photosynthesis in ponderosa pine (900 μmol m^–2 (ground) s^–1), differences in E were more pronounced: 2.4 mmol m^–2 (leaf area) s^–1 for the 12-m trees and 1.2 mmol m^–2 s^–1 for the 36-m trees, yielding g _t of 140 mmol m^–2 (leaf area) s^–1 for the 12-m trees and 72 mmol m^–2 s^–1 for the 36-m trees. Extrapolated to forests with leaf area index =1, the 36-m trees would transpire 117 mm between 1 June and 31 August compared to 170 mm for the 12-m trees, a difference of 15% of average annual precipitation. Lower g _t in the taller trees also likely lowers photosynthesis during the growing season. Received: 19 April 1999 / Accepted: 23 March 2000     

Growth and production of the bivalve <Emphasis Type="Italic">Macoma balthica</Emphasis> (Linnaeus, 1758) (Cardiida: Tellinidae) in the southeastern part of the Baltic Sea

The growth and production of the Baltic clam Macoma balthica in the southeastern part of the Baltic Sea were studied. The shell length of M. balthica reached 23.5 mm, the maximum age was 13+ years. The linear growth was described by the von Bertalanffy equation for shallow-water area (depths 9–40 m): L _τ = 23.99(1 − e ^{−0.1293(τ − (−0.9578))}), and for the deep-water area (41–81 m): L _τ = 20.61(1 − e ^{−0.1813(τ − (−0.5608))}). The annual production was lower (25.35 ± 1.72 kJ/m²) in the shallow-water area than in the deep-water area (71.23 ± 4.48 kJ/m²), with values of P _s /B ratio 0.44 and 0.38, respectively.     

Phytoplankton primary production in a mesotrophic pond in sub-tropical Bangladesh

Annual gross primary productivity in mesotrophic Shahidullah Hall pond (Dhaka, Bangladesh) was 1383.35 g C m⁻² y⁻¹ (arithmetic mean). Daily primary productivity (between 1.6 and 6.8 g C m⁻² d⁻¹ was correlated with chlorophylla, day length and dissolved silica. Chlorophylla related significantly withk, incident light, SRP, alkalinity and conductivity. A negative correlation existed between biomass and rainfall. Productivity, biomass, conductivity, alkalinity, and SRP increased after mid-winter.k, I _k andZ _eu varied according seasonally.P _max related directly with temperature. Seasonal variation of ∝ ^B was 0.0049–0.0258 mg C (mg chla mmol PAR)⁻¹ m⁻². Q₁₀ was 2.12, community respiration 1334.99 g C m⁻² y⁻¹, and the underwater light climate 186.43μE m⁻² s⁻¹.