Batch studies on the removal of gold(III) from aqueous solution by Azolla filiculoides

Azolla filiculoides removed 86% and 100% of gold(III) from initial metal solutions of 2–10 mg gold l^–1 increasing with increased initial concentrations of gold(III). The biomass gave greater than 95% removal efficiency from solution at all biomass concentrations measured. Complete removal of gold occurred at pH 2, with 42% removal at pH 3 and 4, and 63% and 73% removal at pH 5 and 6, respectively. No temperature-dependence removal was observed.     

Optimization of formation and regeneration of protoplasts from biocontrol agents ofTrichoderma species

The optimal conditions necessary for a large yield and a high frequency of regeneration of protoplasts isolated from the biocontrol agentsTrichoderma koningii andT. harzianum were investigated. Protoplast yields were 1.2×10⁸/ml fromT. koningii and 6×10⁷/ml fromT. harzianum when 20-h mycelial culture was treated with a lytic enzyme solution containing Novozym 234 (15 mg/ml), sucrose (0.6 M) and citrate phosphate buffer (0.02 M), pH 5.6 at 31°C. When the protoplasts were grown in the regeneration medium containing yeast extract (1.5%), 1 I of Mandel's salts, pH 5.6, and glucose (0.8 M), a high frequency of regeneration of the protoplast was obseved: 66% forT. koningii and 45% forT. harzianum. Two patterns of regeneration were observed. First, the hyphae arose directly from the regenerated protoplast mother cell. Second, a chain of bud cells developed from the protoplast and subsequently generating hyphae generally protruded from the terminal bud cells.     

Influence of pH and sucrose concentration on nonenzymatic and enzymatic isolation of protoplasts from mature pollen of Tulbaghia violacea

Studies on protoplast isolation were carried out with mature pollen grains of Tulbaghia violacea Harv. (Liliaceae). Pollen grains drifted from surface sterilized crushed anthers were incubated either in a nonenzymatic solution composed of Nitsch medium and sucrose, or in the same solution supplemented with 1% cellulase Onozuka R-10 and 1% Macerozyme R-10. The process of protoplast release was studied as a function of pH and sucrose concentration of nonenzymatic and enzymatic solutions. For nonenzymatic isolation, the tested range of pH and sucrose concentration was from 3.3 to 13.1 and from 0.015 to 1.12 M (final solution osmolality from 200 to 1,300 mOs kg^-1 H₂O), respectively. In the former case, the release of protoplasts occurred only at nonphysiological pH (12.2 to 13.1) and could be observed after several seconds to 120 min, depending on pH and sucrose concentration of medium. Under enzymatic incubation, viable protoplasts were released more rapidly (3 to 35 min) and in more physiological conditions, the optimum being pH 5.8 and final medium osmolality 652 mOs kg^-1 H₂O. Speed, manner of protoplast release, number and quality of protoplasts were dependent on interactions of pH and sucrose concentration.     

pH above 6.0 reduces nodulation in Lupinus species

Lupinus angustifolius and Lupinus pilosus differ substantially in root growth in response to high solution pH with L. angustifolius showing much greater sensitivity to pH above 6. This study examined the effect of pH above 6 on nodulation of these two species in buffered solution. Shoot weight and root weight and length in L. pilosus was not significantly affected by pH, whereas the growth of shoots and roots of L. angustifolius was markedly impaired by increasing pH. Total root length, the number of lateral roots, and the length of individual lateral roots were greatly decreased, resulting in decreased uptake of iron and phosphorus. In addition, L. angustifolius had a higher internal requirement for iron than L. pilosus. A solution pH above 6 decreased the number of nodule initials and nodules similarly in both species but decreased nodule mass much more in L. angustifolius. The effect of high pH on nodule formation occurred prior to that on host shoot growth. High pH also decreased nitrogen concentration and content in both species but to a greater extent for L. angustifolius. The results suggested that pH above 6 has a specific effect in the impairment of nodulation in lupins.     

Influence of alkaline pH on the direct lethal action of miconazole againstCandida albicans

The imidazole group of miconazole is subject to protonation (pKa 6.5). Earlier we suggested that the direct lethal action (DLA) of miconazole againstCandida albicans requires nonprotonated drug molecules. DLA declined in intensity as pH was decreased from 6.0. At pH >6.5 most molecules of miconazole exist in the nonprotonated state, but drug also becomes less soluble. Viability studies were designed to assess DLA in relation to alkaline pH. DLA was clearly inhibited with increasing as well as decreasing pH (i.e., pH <6.0 and >7.0), suggesting that nonprotonated neutral drug molecules must be in solution or in extremely small aggregates to elicit DLA, and that the nonprotonated species itself is more soluble at pH 6.0–7.0 than under more alkaline conditions.     

Stimulation of adventitious rooting of Taxus species by thiamine

Summary Results obtained from using root inducing compounds on Taxus species cuttings suggested that rooting could be significantly enhanced by the presence of thiamine. This observation was verified using a root inducing solution containing a set concentration of IBA (0.2%), NAA (0.1%), and supplemented with various concentrations of thiamine. The best rooting response for Taxus cuspidata stem cuttings was found using this solution supplemented with 0.08% thiamine. Rooted cuttings were easily established and developed into vigorous plants. In addition, Taxus brevifolia shoots obtained from tissue cultures via in vitro organogenesis also responded favorably to this 0.08% thiamine supplemented rooting solution.     

pH buffering in acidic soils developed under Picea abies and Quercus robur – effects of soil organic matter, adsorbed cations and soil solution ionic strength

Soil solution chemistry, soil acidity andcomposition of adsorbed cations were determinedin two soil profiles developed under a mixedspruce (Picea abies and Piceasitchensis) stand and in one soil profiledeveloped under an oak (Quercus robur)stand. Soils under spruce were classified asSpodosols and soils under oak were classifiedas Inceptisols. All profiles were developed inthe same parent material; a Saahlian sandy tillcontaining less than 2% clay. In the mineralsoil, the contribution from mineral surfaces tothe total cation-exchange capacity (CEC_t)was estimated to be less than 3%. Soilsolution pH and the percent base saturation ofCEC_t [%BS = 100 (2Ca + 2Mg + Na + K)CEC_t ^–1] were substantially lower inthe upper 35–40 cm of the two Spodosols, ascompared to the Inceptisol. The total amount ofsoil adsorbed base cations (BC) did not differamong the three profiles on an area basis downto 1 m soil depth. Thus, soil acidification ofCEC_t due to net losses of BC could notexplain differences in soil pH and %BS amongthe soil profiles. A weak acid analogue, takingthe pH-effect of metal complexation intoconsideration, combined with soil solutionionic strength as a covariate, could describeboth the pH variation by depth within soilprofiles and pH differences between theInceptisol and the two Spodosol profiles. Ourresults confirm and extend earlier findingsfrom O and E horizons of Spodosols that theextent to which organic acid groups react withAl minerals to form Al-SOM complexes is a majorpH-buffering process in acidic forest soils. Wesuggest that an increasing Al-saturation of SOMis the major reason for the widely observed pHincrease by depth in acidic forest soils with apH less than approximately 4.5. Our resultsstrongly imply that changes in mass of SOM, theionic strength in soil solution and therelative composition of soil adsorbed Al and Hneed to be considered when the causality behindchanges in pH and base saturation isinvestigated.     

Synergistic antidigestion effect of <Emphasis Type="Italic">Lactobacillus rhamnosus</Emphasis> and bovine colostrums in simulated gastrointestinal tract (in vitro)

Probiotics and bovine colostrums had been proven to be beneficial for human health. Lactobacillus rhamnosus ZDY114 and anti-Helicobacter pylori bovine colostrums were used for the preparation of microecological additives, and their synergistic antidigestion effect in the simulated gastrointestinal tract (in vitro) was investigated. Either L. rhamnosus or purified IgG from immune colostrums was very sensitive in simulated gastric environment and slightly sensitive in simulated intestinal tract. No viable counts were recovered from the solution of dissolved freeze-dried powder (7.14 log₁₀ CFU/ml) of L. rhamnosus when digested at pH 3.0 with pepsin for 30 min. Activity of purified IgGs from immune colostrums could not be detected when digested at pH 3.0 with pepsin for 30 min; 29% titer could be detected when digested at pH 8.0 with trypsin for 5 h. The IgGs in nonpurified immune colostrums presented stronger resistance against gastrointestinal digestion than purified IgGs. Moreover, the combination of L. rhamnosus ZDY114 and immune colostrums strengthened their antidigestion ability. Even under pH 3.0, 4.0 with pepsin, the titer of anti-HP IgG maintained above 123 and 83.3%, respectively. Similarly, that titer was above 93.3% when digested at pH 8.0 with trypsin for 4.5 h. In conclusion, L. rhamnosus and anti-Helicobacter pylori bovine colostrums had synergistic antidigestion effect in simulated gastrointestinal tract (in vitro).     

Isolation of protoplasts from edible seaweeds

Protoplasts were isolated enzymatically from three species of Chlorophyta (Enteromorpha linza, Monostroma zostericola andUlva pertusa) with high yield and viability. An enzyme solution appropriate for protoplast isolation from the marine green algae was the following: 2% Cellulase Onozuka R-10, 1.0.M mannitol, pH 6.0. Protoplasts could not be obtained from members of Phaeophyta or Rhodophyta.     

High pH in the nutrient solution impairs water uptake in Lupinus angustifolius L.

Root growth in Lupinus angustifolius is greatly decreased when the nutrient solution has a pH above 6.0. This study examined the water relations in this species (cv. Yandee) in response to high pH in solution culture in a glasshouse.The dry weight of roots, the length of taproots and lateral roots and the number of lateral roots were significantly reduced at day 12 after transfer to solution with a pH of 7.5 compared to pH 5.2. This resulted in a marked reduction of total root surface area. However, shoot growth and total leaf area were not affected. In comparison with pH 5.2, plants grown at pH 7.5 in the nutrient solution had a 14–38% more-negative leaf water potential, and their stomatal resistance had increased by 67%.The observations indicate that the impairment of the water relations by high pH is mainly caused by decreased root growth.     

Gentiobiose synthesis from glucose using recombinant β-glucosidase from<Emphasis Type="Italic">Thermus caldophilus</Emphasis> GK24

Recombinant β-glucosidase fromThermus caldophilus GK24 was easily purified partially by a heat treatment procedure, resulting in 8-fold and recovery yield of 80% from crude enzyme. When the β-glucosidase was incubated with a 80% glucose solution (w/w), gentiobiose (β1,6-glucobiose) was the major product in the reaction mixture. The optimal conditions for producing gentiobiose (11% yields of total sugar) were pH 8–9 and 70°C for 72 h.     

Expanded bed adsorption as a unique unit operation for the isolation of bacteriocins from fermentation media

Expanded bed adsorption using a strong cation exchanger allowed the direct isolation of amylovorin L471, a bacteriocin from Lactobacillus amylovorusDCE 471, from the fermentation medium. The pH of the loading and elution buffer were optimised in a packed bed with cell-free culture supernatant. Bound bacteriocin was eluted with 1.0 M NaCl. The highest recovery (30%) was obtained at the lowest pH (3.6). At higher pH values the recovery was lower, namely 12%, 15% and 7% at pH 4.5, 6.5 and 8.0, respectively. In expanded bed mode, direct isolation of the bacteriocin from the fermentation medium at pH 3.6 (loading and elution) initially resulted in a recovery of 12%. After optimisation of the pH (loading and elution at pH 3.6 and 6.5, respectively), the recovery for amylovorin L471 increased up to 30% and higher. Recovery of enterocin A from Enterococcus faeciumCTC 492 fermentation medium averaged 15% (loading and elution at pH 3.6 and 6.0, respectively). With pediocin, produced by Pediococcus acidilactici ATCC 8042, 26% recovery was obtained at a pH of 6.5 during loading and elution. Low recoveries can be ascribed to non-optimal operation conditions (pH of loading and elution buffer), inactivation of the bacteriocin on a cationic resin, and the formation of more insoluble and less active, strongly hydrophobic bacteriocin aggregates upon further purification.     

Sorption of Cu(II) and Cd(II) by extracellular polymeric substances (EPS) from Aspergillus fumigatus

Sorption of Cu(II) and Cd(II) onto the extracellular polymeric substances (EPS) produced by Aspergillus fumigatus was investigated for the initial pH of the solution, EPS concentrations, contact time, NaCl concentration, initial metal ion concentration and the presence of other ions in the solution. The results showed that the adsorption of metal ions was significantly affected by pH, EPS concentrations, initial metal concentration, NaCl concentration and co-ions. The sorption of Cu(II) and Cd(II) increased with increasing pH and initial metal ion concentration but decreased with an increase in the NaCl concentration. The maximum sorption capacities of A. fumigatus EPS calculated from the Langmuir model were 40 mg g⁻¹ EPS and 85.5 mg g⁻¹ EPS for Cu(II) and Cd(II), respectively. The binary metal sorption experiments showed a selective metal binding affinity in the order of Cu(II) > Pb(II) > Cd(II). Both the Freundlich and Langmuir adsorption models described the sorption of Cu(II) and Cd(II) by the EPS of A. fumigatus adequately. Fourier transform infrared spectroscopy (FTIR) analysis revealed that carboxyl, amide and hydroxyl functional groups were mainly correlated with the sorption of Cu(II) and Cd(II). Energy dispersive X-ray (EDX) system analysis revealed that the ion-exchange was an important mechanism involved in the Cu(II) and Cd(II) sorption process taking place on EPS.     

Control of relative growth rate by application of the relative addition rate technique to a traditional solution culture system

The relative addition rate (RAR) technique allows the nutritional control of plant relative growth rate (RGR) by the provision of nutrients at exponential supply rates. The technique, however, was developed with technologically sophisticated aeroponic systems. In this paper, we report on experiments used to adapt the RAR technique to a conventional solution culture system. A background concentration requirement of 36 μM nitrogen (N), with other nutrients supplied in proportion to N, was necessary to produce a constant RGR of Triticum aestivum L. (wheat) at a low RAR. Solution pH changes were reduced by increasing the percentage of NH₄ in the nitrogen supply, but the plants exhibited dry weight reductions and symptoms of toxicity above 30% NH₄. For wheat, a ratio of 25/75 NH₄/NO₃ was optimum for minimizing pH changes within the nontoxic range. A test of the effectiveness of the RAR technique using this background concentration and NH₄/NO₃ ratio showed that RGR increased with RAR with a linear slope of 0.55 and an intercept of 0.07 d^-1. Although the relationship between growth rate and nutrient supply was less than the one-to-one dependence of RGR on RAR that has been obtained with more sophisticated apparatus, application of the RAR technique to a conventional solution culture system still affords considerable control of RGR and presents a simple method for growing plants at different levels of nutrient stress and at distinct RGRs.     

Enzymatic isolation of living embryo sacs of Petunia

Summary A 20%–25% yield of isolated and living embryo sacs of Petunia hybrida L. was obtained using an enzymatic maceration mixture containing 3% driselase (soluble fraction only), 0.1% MES buffer, pH 5.5, and 8% mannitol. For each maceration ± 450 ovules were incubated in 1 ml enzyme solution for 2 h at 30° C in a shaking waterbath (150 rpm). Subsequently, the enzyme solution was replaced by Brewbaker and Kwack's medium, pH 6.5, supplemented with 10% mannitol (BKM). Gentle agitation of the suspension resulted in the liberation of embryo sacs, which were then collected with a micropipette using a dissecting microscope and transferred to fresh BKM. The embryo sacs isolated are intact and living, and have maintained their original shape and organization When stored in BKM at room temperature the isolated embryo sacs remain alive for 8 h. Storage at 4° C results in a prolongation of viability of up to 80 h. Prolonged incubation of ovules or reincubation of isolated embryo sacs in the maceration mixture results in the liberation of the gametophytic cells as individual, living protoplasts.     

Physiological responses of lupin roots to high pH

High pH seems to be a major constraint limiting the production of narrow-leafed lupin (Lupinus angustifolius L.) on alkaline soils. Whereas there has been much interest in soil acidity, relatively little is known about the effect of high pH on the growth of roots of higher plants.Elongation of roots of L. angustifolius was particularly sensitive to pH6.0 compared with other species. The effect of high pH in decreasing root elongation in L. angustifolius occurred within one hour. It was via an effect on cell elongation and not cell division and the effect was readily reversible. The mechanisms of the adverse effect of high pH are unknown. The permeability ratio of K⁺ to Na⁺ in the plasma-membrane of the root cortical cells was similar in solutions of both low pH and high pH. Reduced cell growth at high pH was not associated with an inefficiency of proton extrusion to the bulk solution by roots of this species. Nevertheless, increasing buffer concentration in the external solution decreased root elongation more in L. angustifolius than in Lupinus pilosus and Pisum sativum.     

Calcium and temperature effects on seedling exudation and root rot infection of common bean on an acid sandy soil

Soil born fungi such as Phytium ultimum, Fusarium ssp., and Rhizoctonia solani (Kühn) severely restrict stand establishment of common bean (Phaseolus vulgaris L.) on acid soils of the Tropics. Calcium application is known to alleviate fungal infection in many legumes but the causes are still unclear. To investigate environmental factors and physiological mechanisms involved, growth chamber experiments were conducted with an acid sandy soil from Mexico. Treatments were soil liming at a rate of 0.67 g Ca(OH)₂ kg^-1, gypsum application at 0.49 g CaSO₄ 2H₂O kg^-1 soil placed around the seed, and an untreated control. Beans were grown under three temperature regimes with constant night and one constant day vs. two sinusoidal day temperatures. To examine patterns of seed and seedling exudation at regular intervals leachates of germinating seeds were collected on filter paper soaked with equilibrium solutions from soils of the three treatments. The severity of root rot in the control treatment was highest when plants were stressed by temperature extremes. At a sinusoidal day temperature peaking at 40°C soil liming and gypsum application to the seed increased the number of healthy seedlings similarly by over 60%. However, only liming which effectively eliminated growth constraints by low pH and high aluminum concentrations led to an increase in hypocotyl elongation by 22% and in total root length by 8%. Both calcium amendments increased the calcium and potassium contents in the hypocotyl tissue. From seeds exposed to the equilibrium solution of unlimed soil with pH 3.7, 1 mM Ca, and 0.6 mM Al considerable amounts of amino acids and carbohydrates were leached. In contrast, exposure to the equilibrium solution from limed soil with pH 4.3, 3 mM Ca, and negligible concentrations of Al led to a net uptake of amino acids and decreased leaching of carbohydrates. Exposure to the equilibrium solution of the gypsum treatment with pH 3.6, 20 mM Ca, and 1.2 mM Al resulted in a somewhat smaller net uptake of amino acids compared to liming. During germination pH around the seeds steeply increased in the untreated control but significantly less with both amendments. The results indicate that pH and the Ca/Al ratio in the soil solution around bean seeds determine their pattern of exudation and solute uptake. For bean germination and early growth on acid soils locally placed application of small amounts of gypsum as seed pelleting seems as effective as soil liming in reducing the incidence of root rot. The results indicate that this may be accomplished by decreasing the amount of leachates available for fungal development.     

Evaluation of <Emphasis Type="BoldItalic">Sterculia foetida</Emphasis> Gum as Controlled Release Excipient

The purpose of the research was to evaluate Sterculia foetida gum as a hydrophilic matrix polymer for controlled release preparation. For evaluation as a matrix polymer; characterization of Sterculia foetida gum was done. Viscosity, pH, scanning electronmicrographs were determined. Different formulation aspects considered were: gum concentration (10–40%), particle size (75–420 μm) and type of fillers and those for dissolution studies; pH, and stirring speed were considered. Tablets prepared with Sterculia foetida gum were compared with tablets prepared with Hydroxymethylcellulose K15M. The release rate profiles were evaluated through different kinetic equations: zero-order, first-order, Higuchi, Hixon-Crowell and Korsemeyer and Peppas models. The scanning electronmicrographs showed that the gum particles were somewhat triangular. The viscosity of 1% solution was found to be 950 centipoise and pH was in range of 4–5. Suitable matrix release profile could be obtained at 40% gum concentration. Higher sustained release profiles were obtained for Sterculia foetida gum particles in size range of 76–125 μm. Notable influences were obtained for type of fillers. Significant differences were also observed with rotational speed and dissolution media pH. The in vitro release profiles indicated that tablets prepared from Sterculia foetida gum had higher retarding capacity than tablets prepared with Hydroxymethylcellulose K15M prepared tablets. The differential scanning calorimetry results indicated that there are no interactions of Sterculia foetida gum with diltiazem hydrochloride. It was observed that release of the drug followed through surface erosion and anomalous diffusion. Thus, it could be concluded that Sterculia foetida gum could be used a controlled release matrix polymer.     

Biosynthesis of Streptomycin

A method for the accumulation of the streptomycin precursor (L) in the culture broth of Streptomyces griseus was developed and the precursor was successfully isolated from the broth.

When the microorganism was cultured under shaking in the glucose-meat extract-peptone medium (0.5% glucose, 0.2% yeast extract, 0.2% meat extract, 0.4% peptone, 0.5% sodium chloride, 0.025% magnesium sulfate, pH 7.0), the accumulation of the precursor in the broth was induced by the addition of supplementary glucose (e.g., 2 g glucose per 100 ml broth) 24 hr after inoculation followed by further cultivation for 48 hr. Increased accumulation of L component was obtained merely by increasing glucose content in the culture medium (e.g., 5% glucose-containing medium in the above-indicated one) instead of glucose supplement on the way of fermentation. For the accumulation of a large amount of L component in a culture broth, it looked to be necessary for pH value of the broth to be maintained between 6 and 7 during fermentation.

L component was isolated from the culture broth by adsorption on Amberlite IRC-50 and elution with 2% NaCl solution. The L component was separated on this column from contaminated streptomycin which requires 5% NaCl solution to be eluted. The L component in the 2% NaCl eluate was adsorbed on active carbon at neutral or slightly alkaline pH and eluted with 95% methanol at acidic pH, Partially purified L component precipitated as hydrochloride by addition of acetone to the methanol extract which had been concentrated in vacuo.     

Biosorption of Cr, Cu and Al bySargassum biomass

The biosorption and desorption of Cr, Cu and Al were carried out using brown marine algaeSargassum fluitans biomass, known as the good biosorbent of heavy metals. The content of alginate bound to light metals could be changed by physical and chemical pretreatment. The maximum uptake of Cr, Cu and Al was independent of the alginate content. The maximum uptake of Al was two times(mole basis) than those of Cu and Cr. The aluminum-alginate complex was found in the sorption solution of raw and protonated biomass. Most of Cu, Al and light metals sorbed in the biomass were eluted at pH 1.1. However, only 5 to 10% of Cr sorbed was eluted at pH 1.1. The stoichometric ion exchange between Cu and Ca ion was observed on Cu biosorption with Ca-loaded biomass. A part of Cr ion was bound to biomass as Cr(OH)₂ ⁺ or Cr(OH)²⁺. Al was also bound to biomass as multi-valence ion and interfered with the desorbed Ca ion. The behavior of rawS. fluitans in ten consecutive sorption-desorption cycles has been investigated in a packed bed flow-through-column during a continuous removal of copper from a 35 mg/L aqueous solution at pH 5. The eluant used was a 1%(w/v) CaCl/HCl solution at pH3.