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.