Genetically engineered yeast cells enriched with nanocomposites containing a natural enzyme and nanozyme for the construction of microbial sensors.

• A whole cell-based electrochemical biosensor was applied for the assay of methylamine. • A method of enrichment of yeast cells with a target enzyme and nanozyme has been proposed. • Recombinant methylamine oxidase was employed as a specific enzyme. • A synergistic effect of enzyme and nanoparticles inside yeast cells for enhanced catalytic activity was demonstrated. • Selective and sensitive determination of methylamine in food products was demonstrated. Microbial biosensors, particularly when combined with nanotechnologies, are fast and affordable tools for different analytical purposes. Most microbial biosensors are based on the use of genetically modified cells, capable of over-producing a target enzyme, which is advantageous in terms of their sensitivity and selectivity. However, the loss of a plasmid or changes in the number of copies of the plasmid is a significant drawback. In this context, the application of alternative nanotechnological approaches for increasing the catalytic activity of sensing cells is of paramount importance. In the current research, a novel strategy of additional loading of recombinant yeast cells with a target enzyme and nanozyme has been proposed to develop methylamine (MA)-selective biosensor. To construct an amperometric sensor, the Saccharomyces cerevisiae yeast cells were enriched with the enzyme and nanozyme by combining three ways of genetic and nanotechnological engineering: on the genetic level – by overexpression of the methylamine oxidase (MAO) gene coding for MAO in recombinant cells; under nanotechnological approaches – by the additional enrichment of the cells with the purified enzyme MAO, co-immobilized with peroxidase mimetics, i.e. , nCdTe or nCeAu. Fluorescent nCdTe as the most effective peroxidase-mimetic was used to develop hydrogen peroxide chemosensors and as a carrier for delivery of MAO inside the cells. The most effective cells-MAO-nCdTe-containing electrode shows wide range (0.001–0.02 µM) of linear response and high sensitivity (5450 A⋅M−1⋅m−2) to MA. The proposed approaches for increasing catalytic efficiency of sensing cells can be used for elaboration of other microbial sensors based on their enzymatic activity. [Display omitted] [ABSTRACT FROM AUTHOR]