On the Functionalization of Multi-Walled Carbon Nanotubes and Their Application in Nanobiocatalysis

Multi-walled carbon nanotubes (MWCNTs) are functionalized with –OH, –SH, –NH₂, and (3‑glycidyloxypropyl)trimethoxysilane (GLYMO) groups. The enzymatic activity of nanobiocatalysts prepared on the basis of amidase and nitrile hydratase isolated from the cells of the proteobacterium Alcaligenes faecalis 2 and the actinobacterium Rhodococcus ruber gt 1, respectively, and adsorbed on the functionalized MWCNTs (fMWCNTs), is determined. Also, nanobiocatalysts are prepared by aggregating bacterial cells with fMWCNTs; the value of cell aggregation and the manifestation of their enzymatic activity are determined. It is determined that R. ruber gt 1 cells aggregate with all carbon nanomaterials within the range of 16–70 mg/g, and for A. faecalis 2 cells, within the range of 4–84 mg/g. The smallest number of cells are bound to MWCNT–GLYMO, while the high enzymatic activity of the aggregates is retained. Aggregates of A. faecalis 2 with MWCNT–SH exhibit amidase activity exceeding that of native cells. Amidase and nitrile hydratase are bound to nanomaterials to a much lesser extent (no more than 1.7 mg/g). The effect of fMWCNTs on bacterial biofilm formation is studied and a decrease in the total biomass of A. faecalis 2 biofilms, as well as the metabolic activity of their cells, is shown, especially in the presence of MWCNTs-SH and MWCNTs-GLYMO. At the same time, biofilm formation by R. ruber gt 1 in the presence of fMWCNTs increases. Nanobiocatalysts have prospects for practical use due to the advantages of the immobilization of enzymes and microbial cells, as well as a high dispersity and high active surface area of the material.