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Silica-carrageenan hybrids used for cell immobilization realizing high-temperature degradation of nitrile substrates

100%

Kabaivanova L., Chernev G., Miranda Salvado I., Fernandes M.

Open Chemistry

2011

vol. 9

issue 2

232-239

In this work the application of hybrid materials, containing TEOS as source of SiO2 and k-carrageenan in different percentage, synthesized by the sol-gel method at room temperature was studied. They were used as matrices for entrapment of whole Bacillus sp. UG-5B cells, producers of thermostable nitrilase. The effect of the surface area and size and quantity of pores in the synthesized materials on the enzyme activity was evaluated. The process of biodegradation of different concentrations of toxic, potentially carcinogenic and mutagenic substrates by the obtained biocatalysts was investigated. The enzyme reaction takes place by the nitrilase pathway, catalysing nitrile hydrolysis directly to the corresponding carboxylic acid, forming ammonia. At batch experiments the influence of the substrate concentration of different nitriles was tested and 20 mM concentration was found most suitable. A two-step biodegradation process in a laboratory-scale column bioreactor of o-, m- and p-tolunitrile as a mixture was followed. After operation of the system for nine hours for the mixture of substrates at a flow rate of 45 mL h−1 and at 60°C, the overall conversion realized was above 90%, showing a good efficiency of the investigated process.

Organic-inorganic hybrid materials based on N=C=O functionalised silan modified with titanium and zirconium

76%

Ivanova Y., Dimitriev Y., Gerganova T., Bryaskova R., Fernandes M., Miranda Salvado I.

Open Chemistry

2005

vol. 3

issue 3

452-469

This work investigates the influence of the precursor trimethylsilil isocyanate on the sol-gel synthesis of hybrid materials. The obtained Si−O−C−N network is additionally modified by titanium and zirconium alcoxypropoxides in the range of 10 to 30 wt. %. The structure of the obtained hybrid materials before and after pyrolysis up to 1100°C was investigated by methods of XRD, FTIR and 29Si MAS NMR. We established that the hybrid structure was stable up to 600°C based on IR study. The structural transformation of the hybrid materials into oxycarbonitrogen system started at 800°C. The network of the hybrids modified by titanium remained stable and amorphous up to the final temperature of the pyrolysis (1100°C) compared to the gels modified by more than 10 wt.% Zr. It was confirmed by XRD analysis that the last mentioned are nanocomposite materials, built from carbooxynitrogen vitreous matrix and ZrO2-nanocrystals (tetragonal). The NMR method verified the presence of heterometallic bonds (Si−O−Ti and Si−O−Zr) and Q4, ZrQ3 or TiQ3, NSiO3 and D structural units in the gels.

Methylcellulose/SiO2 hybrids: sol-gel preparation and characterization by XRD, FTIR and AFM

76%

Rangelova N., Radev L., Nenkova S., Miranda Salvado I., Vas Fernandes M., Herzog M.

Open Chemistry

2011

vol. 9

issue 1

112-118

Methylcellulose (MC) / SiO2 organic / inorganic hybrid materials have been prepared from MC and methyltriethoxysilane or ethyltrimethoxysilane, and characterized by XRD, FTIR and AFM. XRD showed peak shifts. FTIR shows intermolecular hydrogen bonding between MC and SiO2. AFM depicts surface roughness which depends on the silica precursor and MC content. [...]

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3 Open Chemistry

2 2011

1 2005

3 Miranda Salvado I.

2 Fernandes M.

1 Bryaskova R.

1 Chernev G.

1 Dimitriev Y.

1 Gerganova T.

1 Herzog M.

1 Ivanova Y.

1 Kabaivanova L.

1 Nenkova S.

1 Radev L.

1 Rangelova N.

1 Vas Fernandes M.

Search results

Silica-carrageenan hybrids used for cell immobilization realizing high-temperature degradation of nitrile substrates

Organic-inorganic hybrid materials based on N=C=O functionalised silan modified with titanium and zirconium

Methylcellulose/SiO2 hybrids: sol-gel preparation and characterization by XRD, FTIR and AFM