Co-crystallization of honey with sucrose

Honey was co-crystallized with a sucrose syrup at 128 degrees C using a sucrose:honey proportion of 90:10, 85:15 and 80:20. The first two proportions produced granular co-crystals, whereas the ratio of 80:20 produced a semi-solid product. The granules were relatively free flowing with an angle of repose 38.5-39.5 degrees. Gas chromatography was used to compare die differences in four flavour compounds: 2.3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one, HMF, 6-methyheptyl prop-2-enoate and 3-hydroxy-4-phenylbutan-2-one. Gas chromatographic results indicated some minor differences in the quantity of flavour volatiles in honey relative to the co-crystallized product. (C) 1998 Academic Press Limited.

Co-crystallization of sucrose at high concentration in the presence of glucose and fructose

Co-crystallization of sucrose from a highly concentrated sucrose syrup (less than or equal to 7% moisture, w/w) at 131 degreesC with 0, 5, 10, 15, and 20% of fructose, glucose, or a mixture of fructose and glucose was investigated. The crystallization of sucrose was delayed in presence of these lower molecular weight sugars. The DSC melting endotherm of cocrystallized samples exhibited a decrease in crystalline sucrose in the sample as a function of increased level of glucose and fructose. The mechanical strength of co-crystallized granules was found to be related to the moisture content and the amount of glucose or fructose content in the sample. The samples containing 10, 15, and 20% glucose in co-crystallized product demonstrated crystallization of glucose in its monohydrate form during 1 mo of storage.

Oral administration of a 12% sucrose solution did not decrease behavioural indicators of distress in piglets undergoing tail docking, teeth clipping and ear notching

Sucrose has been shown to attenuate the behavioural response to painful procedures in human infants undergoing circumcision or blood collection via heelstick. Sucrose has also been found to have a behaviour-modifying effect in neonatal rats exposed to a hot plate. The effect was abolished in neonatal rats by injection of the opioid antagonist naltrexone, suggesting that it was mediated by endogenous opioids. In this experiment, the behaviour of 571 newborn Large White x Landrace hybrid piglets in a specific-pathogen-free piggery of the University of Queensland was recorded during and after the routine management practices of tail docking, ear notching and teeth clipping. Piglets were randomly assigned to receive 1.0 ml of a 12% sucrose solution (treatment group) or a placebo (1.0 ml of air) administered via syringe in the mouth, 60 s before commencement of one of the management procedures. Behaviours were recorded at the time of the procedure, and then 2 min after completion of the procedure. Piglets that received the sucrose solution did not behave significantly differently from piglets receiving the placebo. Regardless of whether sucrose or placebo was administered, piglets undergoing the routine management procedures showed significantly greater behavioural responses than piglets undergoing no procedure. It was concluded that under commercial conditions, a 12% sucrose solution administered I min prior to surgery was not effective in decreasing the behavioural indicators of distress in piglets undergoing routine management procedures, Further research into methods of minimising distress caused to piglets by these procedures is recommended.

Thermodynamic non-ideality as an alternative source of the effect of sucrose on the thrombin-catalyzed hydrolysis of peptide p-nitroanalide substrates

The inhibitory effect of sucrose on the kinetics of thrombin-catalyzed hydrolysis of the chromogenic substrate S-2238 (D-phenylalanyl-pipecolyl-arginoyl-p-nitroanilide) is re-examined as a possible consequence of thermodynamic non-ideality-an inhibition originally attributed to the increased viscosity of reaction mixtures. However, those published results may also be rationalized in terms of the suppression of a substrate-induced isomerization of thrombin to a slightly more expanded (or more asymmetric) transition state prior to the irreversible kinetic steps that lead to substrate hydrolysis. This reinterpretation of the kinetic results solely in terms of molecular crowding does not signify the lack of an effect of viscosity on any reaction step(s) subject to diffusion control. Instead, it highlights the need for development of analytical procedures that can accommodate the concomitant operation of thermodynamic non-ideality and viscosity effects.

Dissolution of sucrose crystals in the anhydrous sorbitol melt

The dissolution of a sugar (sucrose as a model) with higher melting point was studied in a molten food polyol (sorbitol as a model) with lower melting point, both in anhydrous state. A DSC and optical examination revealed the dissolution of anhydrous sucrose crystals (mp 192 degreesC) in anhydrous sorbitol (mp 99 degreesC) liquid melt. The sucrose-sorbitol crystal mixtures at the proportions of 10, 30, 60, 100 and 150 g of sucrose per 100 g of sorbitol were heat scanned in a DSC to above melting endotherm of sorbitol but well below the onset temperature of melting of sucrose at three different temperatures 110, 130 and 150 degreesC. The heat scanning modes used were with or without isothermal holding. The dissolution of sucrose in the sorbitol liquid melt was manifested by an increase in the glass transition temperature of the melt and corresponding decrease in endothermic melting enthalpy of sucrose. At given experimental conditions, as high as 25 and 85% of sucrose dissolved in the sorbitol melt during 1 h of isothermal holding at 110 and 150 degreesC, respectively. Optical microscopic observation also clearly showed the reduction in the size of sucrose crystals in sorbitol melt during the isothermal holding at those temperatures. (C) 2003 Elsevier Science Ltd. All rights reserved.

Characterization of Pantoea dispersa UQ68J: producer of a highly efficient sucrose isomerase for isomaltulose biosynthesis

Aims: Isolation, identification and characterization of a highly efficient isomaltulose producer. Methods and Results: After an enrichment procedure for bacteria likely to metabolize isomaltulose in sucrose-rich environments, 578 isolates were screened for efficient isomaltulose biosynthesis using an aniline/diphenylamine assay and capillary electrophoresis. An isolate designated UQ68J was exceptionally efficient in sucrose isomerase activity. Conversion of sucrose into isomaltulose by UQ68J (enzyme activity of 90-100 U mg(-1) DW) was much faster than the current industrial strain Protaminobacter rubrum CBS574.77 (41-66 U mg(-1) DW) or a reference strain of Erwinia rhapontici (0.3-0.9 U mg(-1) DW). Maximum yield of isomaltulose at 78-80% of supplied sucrose was achieved in less than half the reaction time needed by CBS574.77, and the amount of contaminating trehalulose (4%) was the lowest recorded from an isomaltulose-producing microbe. UQ68J is a Gram negative, facultatively anaerobic, motile, noncapsulate, straight rod-shaped bacterium producing acid but no gas from glucose. Based on 16S rDNA analysis UQ68J is closest to Klebsiella oxytoca, but it differs from Klebsiella in defining characteristics and most closely resembles Pantoea dispersa in phenotype. Significance and Impact of Study: This organism is likely to have substantial advantage over previously characterized sucrose isomerase producers for the industrial production of isomaltulose.

Characterisation of xerogels derived from sucrose templated sol-gel synthesis

This work presents the results of the nanostructural characterisation of the effect of sucrose as a template added to a sol derived from a tetraethoxysilane acid catalysed process. By increasing the sucrose template ratio, N-2 adsorption isotherms showed that the xerogel samples changed from a micropore to a mesopore nanostructure as evidenced by the formation of hysteresis at 0.5 partial pressure. In turn, this led to a direct increase in surface areas, pore volumes and average pore sizes. Sucrose has two molecular components of the same molecular weight: D-fructose and D-glucose. D-fructose resulted in the formation of higher pore volumes and pore sizes, while D-glucose formed higher surface area xerogels. Depending of the template ratio employed in the xerogel synthesis, average pore radius ranged from 8.8 to 26 Angstrom, while surface areas increased by over two fold up to 750 m(2) . g(-1). However, pore volumes increased by as much as six fold, from 0.15 to almost 1 cm(3) . g(-1).

Characterization of the highly efficient sucrose isomerase from Pantoea dispersa UQ68J and cloning of the sucrose isomerase gene

Sucrose isomerase (SI) genes from Pantoea dispersa UQ68J, Klebsiella planticola UQ14S, and Erwinia rhapontici WAC2928 were cloned and expressed in Escherichia coli. The predicted products of the UQ14S and WAC2928 genes were similar to known SIs. The UQ68J SI differed substantially, and it showed the highest isomaltulose-producing efficiency in E. coli cells. The purified recombinant WAC2928 SI was unstable, whereas purified UQ68J and UQ14S SIs were very stable. UQ68J SI activity was optimal at pH 5 and 30 to 35 degrees C, and it produced a high ratio of isomaltulose to trehalulose (> 22:1) across its pH and temperature ranges for activity (pH 4 to 7 and 20 to 50 degrees C). In contrast, UQ14S SI showed optimal activity at pH 6 and 35 degrees C and produced a lower ratio of isomaltulose to trehalulose (< 8:1) across its pH and temperature ranges for activity. UQ68J SI had much higher catalytic efficiency; the K-m was 39.9 mM, the V-max was 638 U mg(-1), and the K-cat/K-m was 1.79 x 104 M-1 s(-1), compared to a K-m of 76.0 mM, a V-max. of 423 U mg(-1), and a K-cat/K-m of 0.62 x 104 M-1 s(-1) for UQ14S SI. UQ68J SI also showed no apparent reverse reaction producing glucose, fructose, or trehalulose from isomaltulose. These properties of the P. dispersa UQ68J enzyme are exceptional among purified SIs, and they indicate likely differences in the mechanism at the enzyme active site. They may favor the production of isomaltulose as an inhibitor of competing microbes in high-sucrose environments, and they are likely to be highly beneficial for industrial production of isomaltulose.

Sugarcane ShSUT1: analysis of sucrose transport activity and inhibition by sucralose

Plant sucrose transporters (SUTs) are members of the glycoside-pentoside-hexuronide (GPH) cation symporter family (TC2.A.2) that is part of the major facilitator superfamily (MFS). All plant SUTs characterized to date function as proton-coupled symporters and catalyze the cellular uptake of sucrose. SUTs are involved in loading sucrose into the phloem and sink tissues, such as seeds, roots and flowers. Because monocots are agriculturally important, SUTs from cereals have been the focus of recent research. Here we present a functional analysis of the SUT ShSUT1 from sugarcane, an important crop species grown for its ability to accumulate high amounts of sucrose in the stem. ShSUT1 was previously shown to be expressed in maturing stems and plays an important role in the accumulation of sucrose in this tissue. Using two-electrode voltage clamping in Xenopus oocytes expressing ShSUT1, we found that ShSUT1 is highly selective for sucrose, but has a relatively low affinity for sucrose (K-0.5 = 8.26 mM at pH 5.6 and a membrane potential of -137 mV). We also found that the sucrose analog sucralose (4,1 ',6 '-trichloro-4,1 ',6 '-trideoxygalactosucrose) is a competitive inhibitor of ShSUT1 with an inhibition coefficient (K-i) of 16.5 mM. The presented data contribute to our understanding of sucrose transport in plants in general and in monocots in particular.

The five families of sucrose-phosphate synthase genes in Saccharum spp. are differentially expressed in leaves and stem

Sucrose-phosphate synthase (SPS) is a key enzyme in the pathway of sucrose synthesis. Five different gene families encoding SPS have been reported in the Poaceae [Castleden CK, Aoki N, Gillespie VJ, MacRae EA, Quick WP, Buchner P, Foyer CH, Furbank RT, Lunn JE (2004) Evolution and function of the sucrose-phosphate synthase gene families in wheat and othergrasses. PlantPhysiology 135, 1753-1764]. Expression of the five families in leaf and stem tissues of Saccharum spp. at different stages of development was determined by quantitative real-time PCR. The type B and C families of SPS genes were predominantly expressed in both immature and mature leaves, whereas the two subfamilies making up the type D family were expressed at similar levels in all tissues examined. In the type A family, expression was lowest in leaves and increased from the meristem region down to internode 7 of the stem.

The identification and characterisation of alleles of sucrose phosphate synthase gene family III in sugarcane

Little is known about the extent of allelic diversity of genes in the complex polyploid, sugarcane. Using sucrose phosphate synthase (SPS) Gene (SPS) Family III as an example, we have amplified and sequenced a 400 nt region from this gene from two sugarcane lines that are parents of a mapping population. Ten single nucleotide polymorphisms (SNPs) were identified within the 400 nt region of which seven were present in both lines. In the elite commercial cultivar Q165(A), 10 sequence haplotypes were identified, with four haplotypes recovered at 9% or greater frequency. Based on SNP presence, two clusters of haplotypes were observed. In IJ76-514, a Saccharum officinarum accession, 8 haplotypes were identified with 4 haplotypes recovered at 13% or greater frequency. Again, two clusters of haplotypes were observed. The results suggest that there may be two SPS Gene Family III genes per genome in sugarcane, each with different numbers of different alleles. This suggestion is supported by sequencing results in an elite parental sorghum line, 403463-2-1, in which 4 haplotypes, corresponding to two broad types, were also identified. Primers were designed to the sugarcane SNPs and screened over bulked DNA from high and low Sucrose-containing progeny from a cross between Q165(A) and IJ76-514. The SNP frequency did not vary in the two bulked DNA samples, suggesting that these SNPs from this SPS gene family are not associated with variation in sucrose content. Using an ecotilling approach, two of the SPS Gene Family III haplotypes were mapped to two different linkage groups in homology group 1 in Q165(A). Both haplotypes mapped near QTLs for increased sucrose content but were not themselves associated with any sugar-related trait.

Factors affecting biosynthesis by Xanthomonas albilineans of albicidin antibiotics and phytotoxins

Albicidins are important factors in systemic pathogenesis by Xanthomonas albilineans, which causes the devastating leaf scald disease of sugar cane. They ale also of substantial interest as antibiotics that selectively block prokaryote DNA replication. Albicidin biosynthesis is highly sensitive to medium composition. An optimized, chemically defined medium (SMG3) yielded 30-fold more albicidin from half the accumulated biomass, relative to sucrose peptone (SP) medium. Phosphate starvation stimulated albicidin production in SMG3 and SP media. Addition of other amino acids, ammonium ions or peptones to the defined medium increased the growth rate of X albilineans XA3, but differentially inhibited albicidin biosynthesis. Knowledge of these factors indicates new approaches to understanding mechanisms of pathogenesis and resistance to sugar cane leaf scald disease, and to strain improvement for production of albicidin antibiotics.

Pathway-specific targeting of GAB(A) a receptor subtypes to somatic and dendritic synapses in the central amygdala

Neurons in the central amygdala express two distinct types of ionotropic GABA receptor. One is the classical GABA(A) receptor that is blocked by low concentrations of bicuculline and positively modulated by benzodiazepines. The other is a novel type of ionotropic GABA receptor that is less sensitive to bicuculline but blocked by the GABA(C) receptor antagonist (1,2,5,6-tetrohydropyridine-4-yl) methylphosphinic acid (TPMPA) and by benzodiazepines. In this study, we examine the distribution of these two receptor types. Recordings of GABAergic miniature inhibitory postsynaptic currents (mIPSCs) showed a wide variation in amplitude. Most events had amplitudes of 100 pA. Large-amplitude events also had rise times faster than small-amplitude events. Large-amplitude events were fully blocked by 10 muM bicuculline but unaffected by TPMPA. Small amplitude events were partially blocked by both bicuculline and TPMPA. Focal application of hypertonic sucrose to the soma evoked large-amplitude mIPSCs, whereas focal dendritic application of sucrose evoked small-amplitude mIPSCs. Thus inhibitory synapses on the dendrites of neurons in the central amygdala express both types of GABA receptor, but somatic synapses expressed purely GABA(A) receptors. Minimal stimulation revealed that inhibitory inputs arising from the laterally located intercalated cells innervate dendritic synapses, whereas inhibitory inputs of medial origin innervated somatic inhibitory synapses. These results show that different types of ionotropic GABA receptors are targeted to spatially and functionally distinct synapses. Thus benzodiazepines will have different modulatory effects on different inhibitory pathways in the central amygdala.