Immobilization of enzymatic active substances by immuring inside nanocarbon-in-silica composites

A comparative study of multi-component heterogeneous biocatalysts prepared by immuring enzymatic active substances inside the {nanocarbons-in-silica} composites was carried out. Carbonic materials such as nanotubes, nanofibers, and onion-like nanocarbon were examined for inclusion inside SiO2-based biocatalysts. The properties of the biocatalysts prepared, such as enzyme activity and stability, were studied depending on the content, physicochemical properties and nanostructure of the nanocarbons included. The biomasses of recombinant strain-producer of glucose isomerase Escherichia coli (rec-E.coli) and of baker's yeast autolysates were used for biocatalysts’ preparing. The direct correlation between magnitude of increase of biocatalysts’ steady-state activity and efficiency of adsorption/adhesion of enzymatic active substances (enzyme/cell compartments) on nanocarbons was observed. In the case of weak adsorption of glucose isomerase on carbonic materials, the steady-state activity increased by a factor of 1.5 for the catalysts prepared by immuring rec-E.coli inside the {nanorarbons-in-silica) composites and “dry” cross-linking by glutaric dialdehyde (<1 wt%). In the case of tight adhesion of yeast autolysates on multiwalled carbon nanotubes, the steady-state invertase activity increased by a factor of 6 for the biocatalysts prepared by immuring autolysates inside {MWCNTs-in-silica} composites. The activity of these biocatalysts exceeded ∼3000 U/g, and the half-life time was more than 250 h in the continuous sucrose inversion at 50 °C.

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► Nanocarbon-in-silica composites are studied as a novel matrix for immobilization of enzymatic active substances, in particular recombinant bacterial cells and baker's yeast autolysates.
► The immuring both nanotubes (CNTs), or nanofibers (CNFs), or onion-like nanocarbon (OLNC) and enzymatic active biomass inside SiO2–xerogel leads to enhance steady-state activity of heterogeneous biocatalysts owing to ability of nanocarbons to adsorb/adhere the enzymatic active substances.
► The nanocarbons can be arranged in order of increasing steady-state invertase activity of the biocatalysts prepared: multiwalled CNTs (320 m2/g) ≫ multiwalled CNTs oxidized (330 m2/g) > OLNC (485 m2/g) > CNFs (162 m2/g) ≈ nanodiamonds (325 m2/g).