Metabolism of Monoterpenes : Early Steps in the Metabolism of d-Neomenthyl-beta-d-Glucoside in Peppermint (Mentha piperita) Rhizomes

Previous studies have shown that the monoterpene ketone l-[G-³H] menthone is reduced to the epimeric alcohols l-menthol and d-neomenthol in leaves of flowering peppermint (Mentha piperita L.), and that a portion of the menthol is converted to menthyl acetate while the bulk of the neomenthol is transformed to neomenthyl-β-d-glucoside which is then transported to the rhizome (Croteau, Martinkus 1979 Plant Physiol 64: 169-175). Analysis of the disposition of l-[G-³H]menthone applied to midstem leaves of intact flowering plants allowed the kinetics of synthesis and transport of the monoterpenyl glucoside to be determined, and gave strong indication that the glucoside was subsequently metabolized in the rhizome. Studies with d-[G-³H]neomenthyl-β-d-glucoside as substrate, using excised rhizomes or rhizome segments, confirmed the hydrolysis of the glucoside as an early step in metabolism at this site, and revealed that the terpenoid moiety was further converted to a series of ether-soluble, methanol-soluble, and water-soluble products. Studies with d-[G-³H]neomenthol as the substrate, using excised rhizomes, showed the subsequent metabolic steps to involve oxidation of the alcohol back to menthone, followed by an unusual lactonization reaction in which oxygen is inserted between the carbonyl carbon and the carbon bearing the isopropyl group, to afford 3,4-menthone lactone. The conversion of menthone to the lactone, and of the lactone to more polar products, were confirmed in vivo using l-[G-³H]menthone and l-[G-³H]-3,4-menthone lactone as substrates. Additional oxidation products were formed in vivo via the desaturation of labeled neomenthol and/or menthone, but none of these transformations appeared to lead to ring opening of the p-menthane skeleton. Each step in the main reaction sequence, from hydrolysis of neomenthyl glucoside to lactonization of menthone, was demonstrated in cell-free extracts from the rhizomes of flowering mint plants. The lactonization step is of particular significance in providing a means of cleaving the p-menthane ring to afford an acyclic carbon skeleton that can be further degraded by modifications of the well-known β-oxidation sequence.     

Complexes of Starchy Materials with Organic Compounds

More than one hundred organic compounds have been examined with respect to their precipitation abilities for starch. All the precipitates may be caused subsequent to complex formation between amylose and reagents. A slight change in molecular structure of the reagent often results in a marked change of the complex formation. The complicated nature of the complex formation is discussed. Some of naturally ocurring monoterpenes, especially l-menthone, showed superior properties as selective precipitants for amylose. So the fractionation of starch was attempted using l-menthone and a good result was obtained.     

Kinetics study of pyridine biodegradation by a novel bacterial strain,Rhizobium sp. NJUST18

Biodegradation of pyridine by a novel bacterial strain, Rhizobium sp. NJUST18, was studied in batch experiments over a wide concentration range (from 100 to 1,000 mg l^?1). Pyridine inhibited both growth of Rhizobium sp. NJUST18 and biodegradation of pyridine. The Haldane model could be fitted to the growth kinetics data well with the kinetic constants μ* = 0.1473 h^?1, K _s = 793.97 mg l^?1, K _i = 268.60 mg l^?1 and S _m = 461.80 mg l^?1. The true μ _max, calculated from μ*, was found to be 0.0332 h^?1. Yield coefficient Y _X/S depended on S _i and reached a maximum of 0.51 g g^?1 at S _i of 600 mg l^?1. V _max was calculated by fitting the pyridine consumption data with the Gompertz model. V _max increased with initial pyridine concentration up to 14.809 mg l^?1 h^?1. The q _S values, calculated from $V_{ \hbox{max} }$ , were fitted with the Haldane equation, yielding q _Smax = 0.1212 g g^?1 h^?1 and q* = 0.3874 g g^?1 h^?1 at S _m′ = 507.83 mg l^?1, K _s′ = 558.03 mg l^?1, and K _i′ = 462.15 mg l^?1. Inhibition constants for growth and degradation rate value were in the same range. Compared with other pyridine degraders, μ _max and S _m obtained for Rhizobium sp. NJUST18 were relatively high. High K _i and K _i′ values and extremely high K _s and K _s′ values indicated that NJUST18 was able to grow on pyridine within a wide concentration range, especially at relatively high concentrations.     

Insecticidal activities of monoterpenes and phenylpropenes against <Emphasis Type="Italic">Sitophilus oryzae</Emphasis> and their inhibitory effects on acetylcholinesterase and adenosine triphosphatases

In the present study, six monoterpenes [(?)-citronellal, p-cymene, (?)-menthone, α-pinene, α-terpinene, and (?)-terpinen-4-ol] and two phenylpropenes [trans-cinnamaldehyde and eugenol] were evaluated for their contact and fumigant toxicities against Sitophilus oryzae adults. The effects of these compounds on the mortality of S. oryzae adults in stored wheat and their inhibitory effects on acetylcholinesterase (AChE) and adenosine triphosphatases (ATPases) were examined. The tested compounds showed varying degrees of contact toxicity, with trans-cinnamaldehyde (LC₅₀ = 0.01 mg/cm²) being the most potent compound, followed by (?)-menthone (LC₅₀ = 0.013 mg/cm²) and eugenol (LC₅₀ = 0.015 mg/cm²). In a fumigant toxicity assay, the monoterpenes α-terpinene, p-cymene, and (?)-menthone showed the highest toxicities (LC₅₀ = 50.79, 52.37, and 54.08 μl/L air, respectively). Trans-cinnamaldehyde, (?)-citronellal, and eugenol were the least toxic (LC₅₀ > 100 μl/L air). In general, the oxygenated compounds exhibited high contact toxicities while the hydrocarbon compounds exhibited high fumigant toxicities. When tested for their insecticidal activities against S. oryzae in stored wheat, trans-cinnamaldehyde was found to be the most potent compound, with 73.9% mortality at an application rate of 0.5 g/kg and complete mortality (100%) at 1 and 5 g/kg after 1 week of treatment. All of the tested compounds showed AChE inhibition, although (?)-citronellal and trans-cinnamaldehyde presented the strongest enzyme inhibition, with IC₅₀ values of 18.40 and 18.93 mM, respectively. On the other hand, (?)-terpinene-4-ol exhibited the highest inhibition of ATPases, followed by α-pinene and α-terpinene.     

Observations and models of emissions of volatile terpenoid compounds from needles of ponderosa pine trees growing in situ: control by light,temperature and stomatal conductance

Terpenoid emissions from ponderosa pine (Pinus ponderosa subsp. scopulorum) were measured in Colorado, USA over two growing seasons to evaluate the role of incident light, needle temperature, and stomatal conductance in controlling emissions of 2-methyl-3-buten-2-ol (MBO) and several monoterpenes. MBO was the dominant daylight terpenoid emission, comprising on average 87 % of the total flux, and diurnal variations were largely determined by light and temperature. During daytime, oxygenated monoterpenes (especially linalool) comprised up to 75 % of the total monoterpenoid flux from needles. A significant fraction of monoterpenoid emissions was dependent on light and ¹³CO₂ labeling studies confirmed de novo production. Thus, modeling of monoterpenoid emissions required a hybrid model in which a significant fraction of emissions was dependent on both light and temperature, while the remainder was dependent on temperature alone. Experiments in which stomata were forced to close using abscisic acid demonstrated that MBO and a large fraction of the monoterpene flux, presumably linalool, could be limited at the scale of seconds to minutes by stomatal conductance. Using a previously published model of terpenoid emissions, which explicitly accounts for the physico-chemical properties of emitted compounds, we were able to simulate these observed stomatal effects, whether induced experimentally or arising under naturally fluctuation conditions of temperature and light. This study shows unequivocally that, under naturally occurring field conditions, de novo light-dependent monoterpenes comprise a significant fraction of emissions in ponderosa pine. Differences between the monoterpene composition of ambient air and needle emissions imply a significant non-needle emission source enriched in Δ-3-carene.     

Biosynthesis of mono- and sesqui-terpenes in peppermint from glucose-C and CO2

Labeled glucose and CO₂ are more efficient precursors of monoterpenes in peppermint (Mentha piperita L.) cuttings than is mevalonate, which is the best precursor of sesquiterpenes in this plant. Metabolic turnover of the labeled monoterpenes was observed, in agreement with previous observations. Pulegone derived from ¹⁴CO₂ after 1, 3, 6, 9 and 12 hr of incubation was chemically degraded, and in every case at least 90% of the ¹⁴C-label was found in the seven-carbon fragment containing the isopentenyl pyrophosphate-derived portion of the molecule. The isopropylidene side chain, containing three carbons hypothetically derived from dimethylallyl pyrophosphate, was found to be essentially unlabeled. The results suggest that an endogenous dimethylallyl pyrophosphate pool participates in monoterpene biosynthesis, much as earlier work had suggested that a similar pool participates in sesquiterpene biosynthesis in this plant. These findings are of particular interest because it appears, based on the differential utilization of labeled precursors, that monoterpenes and sesquiterpenes are produced at separate sites in the plant.     

Micropropagation of Cymbidium sinense using continuous and temporary airlift bioreactor systems

Airlift bioreactors were programmed for continuous and temporary immersion culture to investigate factors that affect the rhizome proliferation, shoot formation, and plantlet regeneration of Cymbidium sinense. During rhizome proliferation, the continuous immersion bioreactor system was used to explore the effects of activated charcoal (AC) in the culture medium, inoculation density, and air volume on rhizome differentiation and growth. The optimum conditions for obtaining massive health rhizomes were 0.3 g l^?1 AC in the culture medium, 7.5 g l^?1 inoculation density, and 150 ml min^?1 air. In addition, the temporary immersion bioreactor system was used for both shoot formation and plantlet regeneration. Supplementing 4 mg l^?1 6-benzylaminopurine and 0.2 mg l^?1 naphthalene acetic acid (NAA) to the culture medium promoted shoot induction from the rhizome. Cutting the rhizome explants into 1 cm segments was better for massive shoot formation than cutting into 0.25 and 0.5 cm explant segments. NAA promoted plantlet regeneration and the rooting rate (94.7 %), with whole plantlets growing well in culture medium containing 1.0 mg l^?1 NAA. Therefore, applying bioreactors in C. sinense micropropagation is an efficient way for scaling up the production of propagules and whole plantlets for the industrial production of high-quality seedlings.     

Biodegradation of pyridine by freely suspended and immobilized Pimelobacter sp.

Freely suspended and Ca-alginate-immobilized cells of Pimelobacter sp. were used for degradation of pyridine. When the pyridine concentration was up to 2 g l^–1, freely suspended cells completely degraded pyridine regardless of the initial cell concentrations used. However, when the pyridine concentration increased to 4 g l^–1, the initial cell concentration in freely suspended cell culture should be higher than 1.5 g dry cell weight l^–1 for complete degradation of pyridine. In addition, a freely suspended cell culture with a high initial cell concentration resulted in a high volumetric pyridine-degradation rate, suggesting the potential use of immobilized cells for pyridine-degradation. When the immobilized cells were used for pyridine-degradation, neither specific pyridine-degradation rate nor tolerance against pyridine was improved. However, a high volumetric pyridine-degradation rate in the range 0.082–0.129 g l^–1 hr^–1 could be achieved by the immobilized cells because of the high cell concentration. Furthermore, when the immobilized cells were reused in degrading pyridine at a concentration of 2–4 g l^–1 they did not lose their pyridine-degrading activity for 2 weeks. Taken together, the data obtained here showed the feasibility of using immobilized cells for pyridine-degradation.     

The velocities of ion transport into and through the xylem of roots: findings with a two-point application pulse-chase technique

Excised corn roots, Zea mays, had radioactively labeled solution applied at two points along their length, for 1 minute, and were then kept in dilute, unlabeled nutrient solution. During this “chase” period, exudate was collected at 1-minute intervals, and its content of radioions was determined. Two pulses of label appeared in succession, originating at the points of application near the cut end of the root and farther from the cut end, respectively. Calculation yields the velocity at which the ions moved radially across the root into the xylem (v_r) and the velocity at which they moved longitudinally within the xylem (v_l). For Rb⁺ labeled with ⁸⁶Rb, v_r was 1.8 and v_l, 35 cm/hr. For Br⁻ labeled with ⁸²Br, v_r was 1.4 and v_l, 103 cm/hr.     

Metabolism of Monoterpenes : Metabolic Fate of (+)-Camphor in Sage (Salvia officinalis)

The bicyclic monoterpene ketone (+)-camphor undergoes lactonization to 1,2-campholide in mature sage (Salvia officinalis L.) leaves followed by conversion to the β-d-glucoside-6-O-glucose ester of the corresponding hydroxy acid (1-carboxymethyl-3-hydroxy-2,2,3-trimethyl cyclopentane). Analysis of the disposition of (+)-[G-³H]camphor applied to midstem leaves of intact flowering plants allowed the kinetics of synthesis of the bis-glucose derivative and its transport from leaf to root to be determined, and gave strong indication that the transport derivative was subsequently metabolized in the root. Root extracts were shown to possess β-glucosidase and acyl glucose esterase activities, and studies with (+)-1,2[U-¹⁴C]campholide as substrate, using excised root segments, revealed that the terpenoid was converted to lipid materials. Localization studies confirmed the radiolabeled lipids to reside in the membranous fractions of root extracts, and analysis of this material indicated the presence of labeled phytosterols and labeled fatty acids (C₁₄ to C₂₀) of acyl lipids. Although it was not possible to detail the metabolic steps between 1,2-campholide and the acyl lipids and phytosterols derived therefrom because of the lack of readily detectable intermediates, it seemed likely that the monoterpene lactone was degraded to acetyl CoA which was reincorporated into root membrane components via standard acyl lipid and isoprenoid biosynthetic pathways. Monoterpene catabolism thus appears to represent a salvage mechanism for recycling mobile carbon from senescing oil glands on the leaves to the roots.     

Analysis of [2H7]methionine, [2H4]methionine,methionine, [2H4]homocysteine and homocysteine in plasma by gas chromatography–mass spectrometry to follow the fate of administered [2H7]methionine

Homocysteine plays a key role in several pathophysiological conditions. To assess the methionine–homocysteine kinetics by stable isotope methodology, we developed a simultaneous quantification method of [²H₇]methionine, [²H₄]methionine, methionine, [²H₄]homocysteine and homocysteine in rat plasma by gas chromatography–mass spectrometry (GC–MS). [¹³C]Methionine and [¹³C]homocysteine were used as analytical internal standards to account for losses associated with the extraction, derivatization and chromatography. For labeled and non-labeled homocysteine measurements, disulfide bonds between homocysteine and other thiols or proteins were reduced by dithiothreitol. The reduced homocysteine and methionine species were purified by cation-exchange chromatography and derivatized with isobutyl chlorocarbonate in water–ethanol–pyridine. Quantification was carried out by selected ion monitoring of the molecular-related ions of N(O,S)-isobutyloxycarbonyl ethyl ester derivatives on the chemical ionization mode. The intra- and inter-day precision of the assay was less than 6% for all labeled and non-labeled methionine and homocysteine species. The method is sensitive enough to determine pharmacokinetics of labeled methionine and homocysteine.     

Excretion of Glycolate, Mesotartrate and Isocitrate Lactone by Synchronized Cultures of Ankistrodesmus braunii

Fixation of ¹⁴CO₂ by synchronized cultures of Ankistrodesmus braunii was highest for young growing cells, low for mature cells, and lowest for dividing cells. The amount of ¹⁴C excreted during photosynthesis followed the same trend. Cells at the end of the growing phase, after 10 hours of a 16-hour light phase, excreted nearly 35% of the total ¹⁴C fixed as one product, glycolate. Dividing cells from the dark phase, when tested in the light, excreted only 4% as much glycolate-¹⁴C as the young growing cells. Dividing cells also excreted as much mesotartrate as glycolate and also some isocitrate lactone and an unidentified acid. None of these excreted acids were found inside the cells in significant amounts. Methods for isolation and identification of the excreted acids are present. With ¹⁴C-labeled algae, it was shown that the excretion of glycolate was light-dependent and inhibited by 1,1-dimethyl-3-(p-chlorophenyl) urea. The excretion of labeled mesotartrate, isocitrate lactone, and an unknown acid, but not glycolate, also occurred in the dark. The excreted mesotartrate was predominantly carboxyl-labeled even after long periods of ¹⁴CO₂ fixation. Since glycolate is known to be uniformly labeled, glycolate could not be the precursor of the carboxyl-labeled mesotartrate. The reason for the specific excretion of glycolate, mesotartrate, and isocitrate lactone is not known, but the metabolism of all three acids by the algae may be limited and each can form dilactides or lactones by dehydration. In this context isocitrate lactone was excreted rather than the free acid.     

Pyridine degradation characteristics of a newly isolated bacterial strain and its application with a novel reactor for the further treatment in pyridine wastewater

A pyridine-degrading strain Gemmobacter sp. ZP-12, isolated from an activated sludge, was able to use pyridine as the sole carbon and nitrogen source for the growth. The strain could effectively degrade pyridine and remove TOC over a wide range of initial pyridine concentrations. The pyridine degradation rate for 100, 500, 1000, 1500 and 2000 mg/L was 2.90 ± 0.17; 13.72 ± 0.21, 20.40 ± 0.24, 31.09 ± 0.26, 27.63 ± 0.17 mg/L/h, respectively. During the pyridine degraded, a large amount of NH₄⁺-N was released and accumulated. The accumulation of NH₄⁺-N increased with the increase of pyridine concentration. For further removing the NH₄⁺-N producing in pyridine degradation, an aerobic-moving bed biofilm reactor coupled with intermittent-aeration membrane biological reactor (a-MBBR-IMBR) was constructed, in which the strain and the aerobic / anoxic mixed sludge combined to remove the pollutants in the wastewater containing 500 mg/L pyridine. After 96 h of operation, the final TOC removal efficiency was 96.5 ± 1.05 %. The average residual concentration of NO₃⁻-N and NH₄⁺-N was respectively 9.09 ± 4.13 mg/L and 7.85 ± 3.88 mg/L. The study provides a viable option for treating pyridine wastewater.     

Biofilm Formation and Quorum-Sensing-Molecule Production by Clinical Isolates of Serratia liquefaciens

Serratia spp. are opportunistic human pathogens responsible for an increasing number of nosocomial infections. However, little is known about the virulence factors and regulatory circuits that may enhance the establishment and long-term survival of Serratia liquefaciens in the hospital environment. In this study, two reporter strains, Chromobacterium violaceum CV026 and VIR24, and high-resolution triple-quadrupole liquid chromatography–mass spectrometry (LC-MS) were used to detect and to quantify N-acyl-homoserine lactone (AHL) quorum-sensing signals in 20 S. liquefaciens strains isolated from clinical samples. Only four of the strains produced sufficient amounts of AHLs to activate the sensors. Investigation of two of the positive strains by high-performance liquid chromatography (HPLC)-MS confirmed the presence of significant amounts of short-acyl-chain AHLs (N-butyryl-l-homoserine lactone [C₄-HSL] and N-hexanoyl-l-homoserine lactone [C₆-HSL]) in both strains, which exhibited a complex and strain-specific signal profile that included minor amounts of other short-acyl-chain AHLs (N-octanoyl-l-homoserine lactone [C₈-HSL] and N-3-oxohexanoyl-l-homoserine lactone [OC₆-HSL]) and long-acyl-chain (C₁₀, C₁₂, and C₁₄) AHLs. No correlation between biofilm formation and the production of large amounts of AHLs could be established. Fimbria-like structures were observed by transmission electron microscopy, and the presence of the type 1 fimbrial adhesin gene fimH in all strains was confirmed by PCR. The ability of S. liquefaciens to adhere to abiotic surfaces and to form biofilms likely contributes to its persistence in the hospital environment, increasing the probability of causing nosocomial infections. Therefore, a better understanding of the adherence properties of this species will provide greater insights into the diseases it causes.     

L-lysine Transport in Chicken Jejunal Brush Border Membrane Vesicles

The properties of l-lysine transport in chicken jejunum have been studied in brush border membrane vesicles isolated from 6-wk-old birds. l-lysine uptake was found to occur within an osmotically active space with significant binding to the membrane. The vesicles can accumulate l-lysine against a concentration gradient, by a membrane potential-sensitive mechanism. The kinetics of l-lysine transport were described by two saturable processes: first, a high affinity-transport system (K _mA= 2.4 ± 0.7 μmol/L) which recognizes cationic and also neutral amino acids with similar affinity in the presence or absence of Na⁺ (l-methionine inhibition constant K_iA, NaSCN = 21.0 ± 8.7 μmol/L and KSCN = 55.0 ± 8.4 μmol/L); second, a low-affinity transport mechanism (K_mB= 164.0 ± 13.0 μmol/L) which also recognizes neutral amino acids. This latter system shows a higher affinity in the presence of Na⁺ (K_iB for l-methionine, NaSCN = 1.7 ± 0.3 and KSCN = 3.4 ± 0.9 mmol/L). l-lysine influx was significantly reduced with N-ethylmaleimide (0.5 mmol/L) treatment. Accelerative exchange of extravesicular labeled l-lysine was demonstrated in vesicles preloaded with 1 mmol/L l-lysine, l-arginine or l-methionine. Results support the view that l-lysine is transported in the chicken jejunum by two transport systems, A and B, with properties similar to those described for systems b ^0,+ and y⁺, respectively. Received: 14 August 1995/Revised: 2 April 1996     

Simultaneous utilization of pyridine and fructose by Rhodococcus opacus UFZ B 408 without an external nitrogen source

 A bacterium classified as Rhodococcus opacus, which is able to use pyridine (a potentially growth-inhibiting substrate) as its sole source of carbon, energy and nitrogen, was isolated. In a carbon-limited chemostat culture, the kinetics was determined for growth on both pyridine and a mixture of pyridine and fructose (9 mM/22.15 mM). With growth on pyridine, stable steady states were achieved up to dilution rates of about 0.1 h^-1. A further increase in the dilution rate resulted in the progressive accumulation of pyridine in the culture liquid and the cells were washed out. The maximum specific growth rate (μ_max = 0.23 h^-1) and the K _S value (0.22 mM) for growth on pyridine were determined from the residual pyridine concentrations measured within the range of stable steady states. With growth on the substrate mixture, the specific pyridine consumption rates and the residual pyridine concentrations were lower at similar dilution rates than with growth on pyridine alone, and stable steady states were established at dilution rates of up to 0.13 h^-1. The maximum pyridine degradation rate was enhanced to 270 mg pyridine l^-1 h^-1 compared to 210 mg pyridine l^-1 h^-1with growth on pyridine as a single substrate. An external nitrogen source did not need to be added in the case of growth on the substrate mixture. Fructose was assimilated by means of ammonium released from pyridine. Analysis of the nitrogen balance furnished proof that pyridine is an energy-deficient substrate; pyridine was assimilated and dissimilated at a ratio of 1 mol/0.67 mol respectively. The resulting yield coefficient was about 0.55 g dry weight/g pyridine. Moreover, it was demonstrated that, in regard to the biologically usable energy, 1 mol pyridine corresponds to 0.43 mol fructose. Received: 3 July 1995/Received revision: 19 October 1995/Accepted: 24 October 1995     

l-Glutamate-Dependent Medium Alkalinization by Asparagus Mesophyll Cells : Cotransport or Metabolism?

Mechanically isolated Asparagus sprengeri Regel mesophyll cells cause alkalinization of the suspension medium on the addition of l-glutamate or its analog l-methionine-d,l-sulfoximine. Using a radiolabeled pH probe, it was found that both compounds caused internal acidification whereas l-aspartate did not. Fusicoccin stimulated H⁺ efflux from the cells by 111% and the uptake of l-[U-¹⁴C]glutamate by 55%. Manometric experiments demonstrated that, unlike l-methionine-d,l-sulfoximine, l-glutamate stimulated CO₂ evolution from nonilluminated cells. Simultaneous measurements of medium alkalinization and ¹⁴CO₂ evolution upon the addition of labeled l-glutamate showed that alkalinization was immediate and reached a maximum value after 45 minutes whereas ¹⁴CO₂ evolution exhibited a lag before its appearance and continued in a linear manner for at least 100 minutes. Rates of alkalinization and uptake of l-[U-¹⁴C]glutamate were higher in the light while rates of ¹⁴CO₂ evolution were higher in the dark. The major labeled product of glutamate decarboxylation, γ-aminobutyric acid, was found in the cells and the suspension medium. Its addition to the cell suspension did not result in medium alkalinization and evidence indicates that it is lost from the cell to the medium. The data suggest that the origin of medium alkalinization is co-transport not metabolism, and that the loss of labeled CO₂ and γ-aminobutyric acid from the cell result in an overestimation of the stoichiometry of the H⁺/l-glutamate uptake process.     

Mineralization of diuron [3-(3,4-dichlorophenyl)-1, 1-dimethylurea] by co-immobilized <Emphasis Type="Italic">Arthrobacter</Emphasis> sp. and <Emphasis Type="Italic">Delftia acidovorans</Emphasis>

Mineralization of diuron has not been previously demonstrated despite the availability of some bacteria to degrade diuron into 3,4-dichloroaniline (3,4-DCA) and others that can mineralize 3,4-DCA. A bacterial co-culture of Arthrobacter sp. N4 and Delftia acidovorans W34, which respectively degraded diuron (20 mg l⁻¹) to 3,4-DCA and mineralized 3,4-DCA, were able to mineralize diuron. Total diuron mineralization (20 mg l⁻¹) was achieved with free cells in co-culture. When the bacteria were immobilized (either one bacteria or both), the degradation rate was higher. Best results were obtained with free Arthrobacter sp. N4 cells co-cultivated with immobilized cells of D. acidovorans W34 (mineralization of diuron in 96 h, i.e., 0.21 mg l⁻¹ h⁻¹ vs. 0.06 mg l⁻¹ h⁻¹ with free cells in co-culture).     

Anaerobic degradation of tetrachlorobisphenol-A in river sediment

This study investigated the anaerobic degradation of tetrachlorobisphenol-A (TCBPA) in sediment samples collected at three sites along the Erren River in southern Taiwan. TCBPA anaerobic degradation half-lives (t_1/2) in the sediment were 12.6, 16.9 and 21.7 d at concentrations of 50, 100, and 250 ??g g⁻¹, respectively. TCBPA (50 ??g g⁻¹) anaerobic degradation half-lives (t_1/2) in the sediment were 10.1, 11.8, 11.0, 11.6, 10.8, 9.1, 8.5, 18.2, 19.3, and 16.1 d by the addition of yeast extract (5 mg l⁻¹), cellulose (0.96 mg l⁻¹), sodium chloride (1%), brij 30 (130 mg l⁻¹), brij 35 (43 mg l⁻¹), rhamnolipid (55 ??M), surfactin (91 ??M), phthalic esters (2 mg l⁻¹), nonylphenol (2 mg l⁻¹), and heavy metals (2 mg l⁻¹), respectively. The degradation rate of TCBPA was enhanced by the addition of yeast extract, cellulose, sodium chloride, brij 30, brij 35, rhamnolipid, or surfactin. However, it was inhibited by the addition of phthalic esters, nonylphenol, or heavy metals. Also noted was the presence of dichlorobisphenol-A and bisphenol-A, two intermediate products resulting from the anaerobic degradation of TCBPA accumulated in the sediments.     

Regeneration of peppermint and orange mint from leaf disks

Leaf disks from peppermint, spearmint, orange mint, lavender mint and Scotch spearmint were cultured on various Murashige-Skoog-based media in order to regenerate shoots. A significantly larger average number of orange mint leaf disks regenerated shoots on basal medium containing 44.4 M benzyladenine (BA) and 250 ml l^-1 coconut water (CW). Shoots regenerated from peppermint leaf disks cultured on basal medium containing 44.4 M BA and 250 ml or 450 ml l^-1 CW. The most shoots regenerated from orange mint leaf disks cultured on medium containing 10 g l^-1 washed Difco Bacto-agar. Disks excised from the bases of the first expanding pair of orange mint leaves cultured under dark conditions regenerated a significantly larger average number of shoots. Histological studies suggested that shoots regenerated from the palisade parenchyma cells associated with vascular tissue.Abbreviations BA benzyladenine - NAA 1-naphthaleneacetic acid - TIBA 2,3,5-triiodobenzoic acid - CW coconut water