Neoli Lucyszyn

Electrospinning of commercial guar-gum: Effects of purification and filtration

Guar gums of two different commercial sources were successfully electrospun on both mica and copper tape at several concentrations starting from 1% (w/w). The electrospun fibers formed with the raw materials were not uniform and presented aggregates and beads within the fibers. Two different purification procedures and a filtration sequence with different pore size membranes were applied to enhance galactomannan solution homogeneity and solubility. The consequence was improved fiber morphology. We observed that the precipitation step, within the purification procedure, produced changes in the molar mass distribution and yielded different fiber diameter. Furthermore, spherical aggregates between fibers and within them disappeared after the sequential filtration. The resulting electrospun fiber diameter decreased with membrane pore diameter reduction. We conclude that the filtration process is responsible for molecular disentanglement, as well as disaggregation, which leads to improved electrospun galactomannan fiber morphology.

Property evaluations of dry-cast reconstituted bacterial cellulose/tamarind xyloglucan biocomposites

We describe the mechanical defibrillation of bacterial cellulose (BC) followed by the dry-cast generation of reconstituted BC films (RBC). Xyloglucan (XGT), extracted from tamarind seeds, was incorporated into the defibrillated cellulose at various compositions, and new films were created using the same process. Microscopy and contact angle analyses of films revealed an increase in the microfibre adhesion, a reduced polydispersity in the diameters of the microfibrils and increased hydrophobic behaviour as a function of %XGT. X-ray diffraction analysis revealed changes to the crystallographic planes of the RBC and the biocomposite films with preferential orientation along the (110) plane. Compared with BC, RBC/XGT biocomposite with 10% XGT exhibited improvement in its thermal properties and in Youngs modulus. These results indicated a reorganisation of the microfibres with mechanical treatment, which when combined with hydrocolloids, can create cellulose-based materials that could be applied as scaffolding for tissue engineering and drug release.

Blends of Agar/Galactomannan for Marubakaido Apple Rootstock Shoot Proliferation

Galactomannans (GMs) extracted from seeds of a native Brazilian specie designated Cassia fastuosa (cassia) and from Cyamopsis tetragonolobus (guar gum - a commercial GM) were mixed with agar, in the proportion of 3/3 g.L -1 (w/w), and used as a gelling agent in Marubakaido apple rootstock (Malus prunifolia Borkh) micropropagation. The rheological measurements of the gels showed a good interaction between both hidrocolloids. The micropropagation results on these media were compared with behaviour of standard medium containing agar only (6 g.L -1 ). Results from in vitro experiments indicated enhanced proliferation of apple shoots and also the occurrence of hyperhydric shoots was lower in the modified gel-medium.

Assembling of xyloglucans and lectin onto si wafers and onto amino-terminated surfaces

A imobilizacao de xiloglucanas (XG) extraidas de sementes de Hymenaea coubaril (HXG) e de Tamarindus indica (TXG) sobre lâminas de Si/SiO2 ou lâminas modificadas com grupos amina a partir de solucao aquosa na concentracao de 0,5 g L-1 e em pH 3,5 foi investigada atraves de elipsometria e medidas de microscopia de forca atomica (AFM). Os experimentos foram feitos sob condicoes de equilibrio (adsorcao) ou de nao equilibrio (evaporacao do solvente). Sob condicoes de equilibrio as cadeias de HXG e TXG nao adsorvem sobre lâminas de Si/SiO2, indicando que os grupos SiO- na superficie nao interagem com as mesmas. Camadas de TXG e HXG obtidas sobre lâminas de Si/SiO2 por evaporacao do solvente apresentaram espessuras de (2,4 ± 0,4) nm e (3,8 ± 0,9) nm, respectivamente. Cadeias de TXG e HXG adsorveram sobre lâminas modificadas com grupos amina formando filmes com (1,0 ± 0,1) nm e (1,3 ± 0,1) nm de espessura, respectivamente. Apos evaporacao do solvente sobre lâminas modificadas com grupos aminas, formaram-se agregados e fibrilas de TXG e HXG, os quais aumentaram os valores medios de espessura e rugosidade. Independentemente do tipo de substrato, cadeias de HXG tenderam a formar camadas mais espessas que cadeias TXG. Esta tendencia foi explicada com base nas caracteristicas moleculares das cadeias de HXG, como por exemplo, massa molar e tamanho de persistencia maiores. As isotermas de adsorcao de concanavalina A (Con A) sobre TXG e HXG adsorvidas sobre lâminas modificadas com grupos amina apresentaram valor maximo de (3,3 ± 0,3) mg m-2. Imagens de AFM mostraram moleculas de Con A densamente empacotadas sobre as superficies de TXG e HXG. Fibrilas e agregados foram observados somente quando as superficies de TXG e HXG foram preparadas por evaporacao do solvente. Nesta situacao, as moleculas de Con A adsorveram predominantemente sobre regioes livres de fibrilas e agregados.

Galactomannan thin films as supports for the immobilization of Concanavalin A and/or dengue viruses.

The immobilization of the glucose/mannose-binding lectin from Concanavalia ensiformis seeds (ConA) onto a monolayer made of a galactomannan extracted from Leucaena leucocephala seeds (GML), which was adsorbed onto - amino-terminated surfaces, was investigated by means of ellipsometry and atomic force microscopy. The mean thickness of GML monolayer, which polysaccharide consists of linear 1→4-linked β-D-mannopyranosil units partially substituted at C-6 by α-D-galactopyranosyl units, amounted to (1.5±0.2) nm. ConA molecules adsorbed onto GML surfaces forming (2.0±0.5) nm thick layers. However, in the presence of mannose the adsorption failed, indicating that ConA binding sites were blocked by mannose and were no longer available for mannose units present in the GML backbone. The GML film was also used as support for the adsorption of three serotypes of dengue virus particles (DENV-1, DENV-2 and DENV-3), where DENV-2 formed the thickest film (4±2) nm. The adsorbed layer of DENV-2 onto ConA-covered GML surfaces presented mean thickness values similar to that determined for DENV-2 onto bare GML surfaces. The addition of free mannose units prevented DENV-2 adsorption onto ConA-covered GML films by ~50%, suggesting competition between virus and mannose for ConA binding sites. This finding suggests that if ConA is also adsorbed to GML surface and its binding site is blocked by free mannose, virus particles are able to recognized GML mannose unities substituted by galactose. Interactions between polysaccharides thin films, proteins, and viruses are of great relevance since they can provide basis for the development of biotechnological devices. These results indicate that GML is a potential polysaccharide for biomaterials development, as those could involve interactions between ConA in immune system and viruses.

Agar/galactomannan gels applied to shoot regeneration from tobacco leaves

This study concerns the efficacy of partial agar substitution by galactomannans as support in plant regeneration media for Nicotiana tabacum. The production of multiple shoots from leaf-derived callus and their rooting were evaluated. The galactomannans applied were obtained from Cassia fastuosa (cassia) and Cyamopsis tetragonolobus (guar gum — a commercial galactomannan) seeds. The results obtained on media solidified with mixtures of agar/galactomannan (3 g dm−3 each) gels were compared with those on media gelled with a standard concentration of agar (6 g dm−3). The in vitro performance allowed to conclude that the use of galactomannans raised the number of shoots and improved their quality. Furthermore, the length of roots and the size of leaves were significantly higher in the media solidified with agar/guar galactomannan mixtures.

MICROPROPAGATION OF ‘DURONDEAU’ PEAR IN MODIFIED-GELLED MEDIUM

SummaryThe influence of partial substitution of agar by galactomannans (GMs) in culture media was studied in pear (Pyrus communis L. cv. ‘Durondeau’) micropropagation. GMs. extracted from seeds of Cassia fastuosa (cassia) or Cyamopsis tetragonolobus (guar gum, a commercial GM), were mixed in equal proportions with agar to a final concentration of 0.3% (w/v) for each type of gelling agent. The production of multiple shoots and the formation of roots from shoots were compared with the control solidified with agar alone at a concentration of 0.6% (w/v). In the media solidified with the mixtures of agar/guar and agar/cassia GMs, an, increase of 32 and 17%, respectively, was obtained in the number of regenerated shoots. The modified media promoted a higher number of roots and increased the rooting percentage. A maximum of 91% rooting was obtained in the medium solidified with the agar/cassia GM and containing 9.80 μM indole-3-butyric acid. Less callus formation at the base of the shoot was also observed on this medium. The improved in vitro performance of shoot formation and rooting, combined with a significantly lower cost, suggests a potential use of agar/GM gels in plant tissue culture.

TEMPO-mediated oxidation on galactomannan: Gal/Man ratio and chain flexibility dependence

Guar (GG) and locust bean (LBG) galactomannans (GMs) oxidation at C-6 was performed with catalyst TEMPO, in which the reaction progress was monitored by consume of NaOH solution. The products were characterized by spectroscopic analysis, infrared, and (1)H-nuclear magnetic resonance, confirming the presence of aldehydes groups as intermediate of reaction to carboxylic acid. From high performance anion exchange chromatography with pulsed amperometric detection Man/Gal molar ratio was determined and demonstrated a preference to oxidize Man during the reaction on both GMs, following a first order kinetics of oxidation. The comparative macromolecular behavior of native and oxidized GMs was obtained through the analysis by high performance size exclusion chromatography, and the persistence length (Lp) was 6nm and 4nm to native LBG and GG, respectively. A more accessible OH-6 at mannose residue in LBG could be related with a two times faster reaction than GG. The selective oxidation with catalyst TEMPO proved to be efficient to increase the flexibility of the GMs during oxidation. Short reaction time and β-elimination process were mainly observed to LBG, probably due to a more favorable oxidation access to the polysaccharide main chain.

Nanometric organisation in blends of gellan/xyloglucan hydrogels

Mixtures of gellan gum (GL) and a xyloglucan (XGJ) extracted from Hymenaea courbaril seeds were prepared in a solution of 0.15 mol L(-1) NaCl. Rheology measurements revealed that 2.4 g L(-1) pure GL formed a brittle hydrogel, and GL-XGJ blends showed improved pseudoplastic character with higher XGJ contents. SAXS analyses showed that the Rg dimensions ranged from 1.3 to 4.9 nm, with larger values occurring as the amount of XGJ increased, and diffusion tests indicated that better diffusion of methylene blue dye was obtained in the network with a higher XGJ content. AFM topographic images of the films deposited onto mica revealed fewer heterogeneous surfaces with increased XGJ contents. The water contact angle revealed more hydrophobic character on all of the films, and the wettability decreased with increasing amounts of XGJ. Therefore, the demonstrated benefit of using XGJ blends is the production of a soft material with improved interface properties.

Effect of agar, galactomannan and indole-butyric acid on in vitro rooting of the pear cultivar 'Durondeau' and apple rootstock cultivar 'Marubakaido'

Summary The influence of partial substitution of agar by galactomannans in culture media supplemented with different concentrations of indole-3-butyric acid (IBA) was studied on in vitro rooting of pear (Pyrus communis L.) cultivar ‘Durondeau’ and apple rootstock (Malus prunifolia Borkh.) cultivar ‘Marubakaido’. The galactomannans applied were obtained from Cassia fastuosa (cassia) and Cyamopsis tetragonolobus (guar gum) seeds. The results obtained with mixtures of agar and galactomannan (3 g l–1 each) were compared with those from media solidified with a standard concentration of agar (6 g l–1). The rooting of pear shoots was enhanced significantly in the presence of a mixture of agar plus cassia galactomannan compared to medium solidified with agar only. The modified media promoted a higher number of roots than the control, and increased the percentage of rooted shoots. A maximum of 84.8% rooting was obtained on half-strength MS medium (1⁄2MS) supplemented with 0.49 µM IBA and solidified with a blend of agar plus cassia galactomannan. For the apple rootstock, only the number of roots per shoot was influenced significantly by the addition of galactomannan to the rooting medium. The highest number of roots per shoot was 16.67 on 1⁄2MS medium gelled with a mixture of agar plus guar galactomannan supplemented with 4.90 µM IBA. The behaviour of the agar-galactomannan gel and the possibility of reduced costs when compared with systems containing only agar, suggest new biological and commercial applications for galactomannans.