Investigation into the ability of Gluconacetobacter sacchari to live as an endophyte in sugarcane

The relatively low numbers and sporadic pattern of incidence of the acetic acid bacterium Gluconacetobacter sacchari with the pink sugarcane mealybug (PSMB) Saccharicoccus sacchari Cockerell (Homoptera: Pseudococcidae) over time and from different sugarcane-growing regions do not indicate that Glac. sacchari is a significant commensal of the PSMB, as has been previously proposed. This study was conducted to investigate the hypothesis that Glac. sacchari is, like its closest relative Glac. diazotrophicus, an endophyte of sugarcane (Saccharum officinarium L.). In this study, both Glac. sacchari and Glac. diazotrophicus were isolated from internal sugarcane tissue, although the detection of both species was sporadic in all sugarcane-growing regions of Queensland tested. To confirm the ability of Glac. sacchari to live endophytically, an experiment was conducted in which the roots of micropropagated sugarcane plantlets were inoculated with Glac. sacchari, and the plantlets were subsequently examined for the presence of the bacterium in the stem cells. Pure cultures of Glac. sacchari were grown from homogenized surface sterilized sugarcane stems inoculated with Glac. sacchari. Electron microscopy was used to provide further conclusive evidence that Glac. sacchari lives as an endophyte in sugarcane. Scanning electron microscopy of (SEM) sugarcane plantlet stems revealed rod-shaped cells of Glac. sacchari within a transverse section of the plantlet stem cells. The numbers of bacterial cells inside the plant cell indicated a successful infection and colonization of the plant tissue. Using transmission electron microscopy, (TEM) bacterial cells were more difficult to find, due to their spatial separation. In our study, bacteria were mostly found singularly, or in groups of up to four cells inside intercellular spaces, although bacterial cells were occasionally found inside other cells.

Molecular investigation of the microbial populations of the pink sugarcane mealybug, Saccharicoccus sacchari

In an attempt to better understand the microbial diversity and endosymbiotic microbiota of the pink sugarcane mealybug (PSMB) Saccharicoccus sacchari Cockerell (Homoptera: Pseudococcidae), culture-independent approaches, namely PCR, a 16S rDNA clone library, and temperature gradient gel electrophoresis (TGGE) were used. Previous work has indicated that the acetic acid bacteria Gluconacetobacter sacchari, Gluconacetobacter diazotrophicus, and Gluconacetobacter liquefaciens represent only a small proportion of the microbial community of the PSMB. These findings were supported in this study by TGGE, where no bands representing G. sacchari, G. diazotrophicus, and G. liquefaciens on the acrylamide gel could be observed following electrophoresis, and by a 16S rDNA clone library study, where no clones with the sequence of an acetic acid bacterium were found. Instead, TGGE revealed that the mealybug microbial community was dominated by beta- and gamma-Proteobacteria. The dominant band in TGGE gels found in a majority of the mealybug samples was most similar, according to BLAST analysis, to the beta-symbiont of the craw mealybug Antonina crawii and to Candidatus Tremblaya princeps, an endosymbiont from the mealybug Paracoccus nothofagicola. The sequences of other dominant bands were identified as gamma-Proteobacteria, and were most closely related to uncultured bacterial clones obtained from soil samples. Mealybugs collected from different areas in Queensland, Australia, were found to produce similar TGGE profiles, although there were a few exceptions. A 16S rDNA clone library based on DNA extracted from a mealybug collected from sugarcane in the Burdekin region in Queensland, Australia, indicated very low levels of diversity among mealybug microbial populations. All sequenced clones were most closely related to the same members of the gamma-Proteobacteria, according to BLAST analysis.

Adventitious root formation in Grevillea (Proteaceae), an Australian native species

Grevillea (Proteaceae) is a native Australian plant genus with high commercial value as landscape ornamentals. There has been limited research on the culture and propagation of Australian native species. The effect of indole-3-butyric acid (IBA) on the rooting of G. 'Royal Mantle' and G. 'Coastal Dawn' in winter, spring and summer was evaluated at University of Queensland Gatton, Southern Queensland in order to determine the rooting ability of this species in different seasons. Both Grevillea cultivars showed seasonal rooting. The more difficult-to-root G. 'Coastal Dawn' had a reduced response to IBA application than G. 'Royal Mantle'. Stem and leaf indole-3-acetic acid (IAA) levels were not different between cultivars, therefore rooting ability between the two cultivars does not appear to be due to the differences in endogenous IAA levels. (c) 2005 Elsevier B.V. All rights reserved.

Axillary bud outgrowth: sending a message

Mutants that branch profusely in the presence of a growing shoot tip have highlighted the role of graft-transmissible signals that are produced in roots and stem. Orthologous genes in Arabidopsis, pea and petunia are involved in the transmission of a novel long-distance message. These genes show varying degrees of regulation by auxin and an auxin-independent feedback system, and encode enzymes that might act on carotenoid-like substrates. Axillary bud outgrowth is under homeostatic control, involving developmental stages or checkpoints. Perturbation of the long-range messaging and auxin depletion does not guarantee that bud outgrowth will ensue at a particular node.

Effects of solids concentration, pH and carbon addition on the production rate and composition of volatile fatty acids in prefermenters using primary sewage sludge

Increasing evidence is emerging that the performance of enhanced biological phosphorus removal (EBPR) systems relies on not only the total amount but also the composition of volatile fatty acids (VFAs). Domestic wastewater often contains limited amounts of VFAs with acetic acid typically being the dominating species. Consequently, prefermenters are often employed to generate additional VFAs to meet the demand for carbon by EBPR and/or denitrification processes. Limited knowledge is currently available on the effects of operational conditions on the production rate and composition of VFAs in prefermenters. In this study, a series of controlled batch experiments were conducted with sludge from a full-scale prefermenter to determine the impact of solids concentration, pH and addition of molasses on prefermentation processes. It was found that an increase in solids concentration enhanced total VFA production with an increased propionic acid fraction. The optimal pH for prefermentation was in the range of 6-7 with significant productivity loss when pH was below 5.5. Molasses addition significantly increased the production of VFAs particularly the propionic acid. However, the fermentation rate was likely limited by the biological activity of the sludge rather than by the amount of molasses added.

Branching genes are conserved across species. Genes controlling a novel signal in pea are coregulated by other long-distance signals

Physiological and genetic studies with the ramosus (rms) mutants in garden pea (Pisum sativum) and more axillary shoots (max) mutants in Arabidopsis (Arabidopsis thaliana) have shown that shoot branching is regulated by a network of long-distance signals. Orthologous genes RMS1 and MAX4 control the synthesis of a novel graft-transmissible branching signal that may be a carotenoid derivative and acts as a branching inhibitor. In this study, we demonstrate further conservation of the branching control system by showing that MAX2 and MAX3 are orthologous to RMS4 and RMS5, respectively. This is consistent with the longstanding hypothesis that branching in pea is regulated by a novel long-distance signal produced by RMS1 and RMS5 and that RMS4 is implicated in the response to this signal. We examine RMS5 expression and show that it is more highly expressed relative to RMS1, but under similar transcriptional regulation as RMS1. Further expression studies support the hypothesis that RMS4 functions in shoot and rootstock and participates in the feedback regulation of RMS1 and RMS5 expression. This feedback involves a second novel long-distance signal that is lacking in rms2 mutants. RMS1 and RMS5 are also independently regulated by indole-3-acetic acid. RMS1, rather than RMS5, appears to be a key regulator of the branching inhibitor. This study presents new interactions between RMS genes and provides further evidence toward the ongoing elucidation of a model of axillary bud outgrowth in pea.

Siderophore activity of myo-inositol hexakisphosphate in Pseudomonas aeruginosa

Myo-Inositol hexakisphosphate (InsP6), which is found in soil and most, if not all, plant and animal cells, has been estimated to have an affinity for Fe3+ in the range of 10(25) to 10(30) M-1. In this report, we demonstrate that the Fe-InsP6 complex has siderophore activity and is able to reverse the iron-restricted growth inhibition of Pseudomonas aeruginosa by ethylene diamine di(o-hydroxyphenyl)acetic acid. With 55Fe-InsP6 in transport studies, iron uptake is strongly iron regulated, being repressed after growth in iron-replete conditions and inhibited by treatment with potassium cyanide and carbonyl cyanide m-chlorophenylhydrazone. The kinetics of iron transport revealed a Km of 100 nM. Self-displacement of binding of [3H]InsP6 to isolated membranes by InsP6 revealed a single class of binding sites (Kd = 143 +/- 6 nM; Hill coefficient, 1.1 +/- 0.1). The binding of [3H]InsP6 to membranes was not dependent on whether cells had been grown under conditions of high or low iron concentrations. We believe that this is the first report of inositol polyphosphate activity in prokaryotic cells.

Advanced liquid-liquid extraction : studies in a laboratory mixer-settler

A ten stage laboratory mixer-settler has been designed, constructed and operated with efficiencies up to 90%. The phase equilibrium data of the system acetic acid-toluene-water at different temperatures has been determined and correlated. Trials for prediction of these data have been investigated and a good agreement between the experimental data and the predictions obtained by the NRTL equation have been found. Extraction processes have been analysed. A model for determination of the time needed for a countercurrent stage-wise process to come to steady state has been derived. The experimental data was in reasonable agreement with this model. The discrete maximum principle has been applied to optimize the countercurrent extraction process and proved to be highly successful in predicting the optimum operating conditions which were confirmed by the experimental results. The temperature has proved to be a prosolvent for mass transfer in both directions but the temperature profile functioned as an anti solvent.

A convenient synthesis of 5-benzylidenethiazolidine-2, 4-diones under microwave irradiation without solvent

A series of 5-benzylidenethiazolidine-2,4-diones was synthesised by the Knoevenagel condensation of aromatic aldehydes with thiazolidine-2,4-dione in the presence of catalytic amounts of piperidine and acetic acid under microwave irradiation without solvent in good yields.

Fast pyrolysis of cassava rhizome in the presence of catalysts

Cassava rhizome was catalytically pyrolysed at 500 °C using analytical pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) in order to investigate the effect of catalysts on bio-oil properties. The catalysts studied were zeolite ZSM-5, two aluminosilicate mesoporous materials Al-MCM-41 and Al-MSU-F, and a proprietary commercial catalyst alumina-stabilised ceria MI-575. The influence of catalysts on pyrolysis products was observed through the yields of aromatic hydrocarbons, phenols, lignin-derived compounds, carbonyls, methanol and acetic acid. Results showed that all the catalysts produced aromatic hydrocarbons and reduced oxygenated lignin derivatives, thus indicating an improvement of bio-oil heating value and viscosity. Among the catalysts, ZSM-5 was the most active to all the changes in pyrolysis products. In addition, all the catalysts with the exception of MI-575 enhanced the formation of acetic acid. This is clearly a disadvantage with respect to the level of pH in the liquid bio-fuel.

Vapour-liquid equilibrium studies at atmospheric to moderate pressures

A study of vapour-liquid equilibria is presented together with current developments. The theory of vapour-liquid equilibria is discussed. Both experimental and prediction methods for obtaining vapour-liquid equilibria data are critically reviewed. The development of a new family of equilibrium stills to measure experimental VLE data from sub-atmosphere to 35 bar pressure is described. Existing experimental techniques are reviewed, to highlight the needs for these new apparati and their major attributes. Details are provided of how apparatus may be further improved and how computer control may be implemented. To provide a rigorous test of the apparatus the stills have been commissioned using acetic acid-water mixture at one atmosphere pressure. A Barker-type consistency test computer program, which allows for association in both phases has been applied to the data generated and clearly shows that the stills produce data of a very high quality. Two high quality data sets, for the mixture acetone-chloroform, have been generated at one atmosphere and 64.3oC. These data are used to investigate the ability of the new novel technique, based on molecular parameters, to predict VLE data for highly polar mixtures. Eight, vapour-liquid equilibrium data sets have been produced for the cyclohexane-ethanol mixture at one atmosphere, 2, 4, 6, 8 and 11 bar, 90.9oC and 132.8oC. These data sets have been tested for thermodynamic consistency using a Barker-type fitting package and shown to be of high quality. The data have been used to investigate the dependence of UNIQUAC parameters with temperature. The data have in addition been used to compare directly the performance of the predictive methods - Original UNIFAC, a modified version of UNIFAC, and the new novel technique, based on molecular parameters developed from generalised London's potential (GLP) theory.

Enzyme catalysed modification of polymers

The aim of this project was to investigate the enzyme catalysed modification of synthetic polymers. It was found that an immobilised lipase from Candida antartica (Novozyme 435) catalysed the selective epoxidation of poly(butadiene) in the presence of hydrogen peroxide and catalytic quantities of acetic acid. The cis and trans double bonds of the backbone were epoxidised in yields of up to 60 % whilst the pendent vinyl groups were untouched. The effect of varying a number of reaction parameters was investigated. These studies suggested that higher yields of epoxide could not be obtained because of the conformational properties of the partially epoxidised polymer. Application of this process to the Baeyer-Villiger reaction of poly(vinyl phenyl ketone) and poly(vinyl methyl ketone) were unsuccessful. The lack of reactivity was found to be a property of the polymer rather than the enzymatic system employed. Attempts to modify hydroxyl containing polymers and polymers bearing active esters close to the polymer backbone were unsuccessful. Steric factors appear to be the most important influence on the outcome of the reactions.

The separation of hydrogen and carbon monoxide using polymer membranes

This work studies the development of polymer membranes for the separation of hydrogen and carbon monoxide from a syngas produced by the partial oxidation of natural gas. The CO product is then used for the large scale manufacture of acetic acid by reaction with methanol. A method of economic evaluation has been developed for the process as a whole and a comparison is made between separation of the H2/CO mixture by a membrane system and the conventional method of cryogenic distillation. Costs are based on bids obtained from suppliers for several different specifications for the purity of the CO fed to the acetic acid reactor. When the purity of the CO is set at that obtained by cryogenic distillation it is shown that the membrane separator offers only a marginal cost advantage. Cost parameters for the membrane separation systems have been defined in terms of effective selectivity and cost permeability. These new parameters, obtained from an analysis of the bids, are then used in a procedure which defines the optimum degree of separation and recovery of carbon monoxide for a minimum cost of manufacture of acetic acid. It is shown that a significant cost reduction is achieved with a membrane separator at the optimum process conditions. A method of "targeting" the properties of new membranes has been developed. This involves defining the properties for new (hypothetical -yet to be developed) membranes such that their use for the hydrogen/carbon monoxide separation will produce a reduced cost of acetic acid manufacture. The use of the targeting method is illustrated in the development of new membranes for the separation of hydrogen and carbon monoxide. The selection of polymeric materials for new membranes is based on molecular design methods which predict the polymer properties from the molecular groups making up the polymer molecule. Two approaches have been used. One method develops the analogy between gas solubility in liquids and that in polymers. The UNIFAC group contribution method is then used to predict gas solubility in liquids. In the second method the polymer Permachor number, developed by Salame, has been correlated with hydrogen and carbon monoxide permeabilities. These correlations are used to predict the permeabilities of gases through polymers. Materials have been tested for hydrogen and carbon monoxide permeabilities and improvements in expected economic performance have been achieved.