⎯The relevant sol-gel encapsulation methods to design ORMOSIL (organically modified silica) protective shells around Debaryomyces hansenii yeast cells have been studied. Encapsulation is based on spontaneous "cell-in-shell" 3D structures. The physiological activity of the sol-gel encapsulated cells was determined by measurement of the oxidative activity of a BOD biosensor containing ORMOSIL-encapsulated cells. It was shown that the shells around the microbial cells did not prevent substrate diffusion and had excellent protection from extreme environmental factors (heavy metal ions, high pH, and UV radiation). In addition, it was found that the BOD biosensor surpasses some other known biosensors in their basic characteristics, including sensitivity, stability, and reproducibility. These results are important for the development of innovative methods of cell encapsulation and the creation of biocatalysts used in biotechnology and ecology.

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Biocatalysts based on the methylotrophic yeast Ogataea polymorpha VKM Y-2559 immobilized in polymer-based nanocomposites for the treatment of methanol-containing wastewater were developed. The organosilica composites with different matrix-to-filler ratios derived from TEOS/MTES in the presence of PEG (SPEG-composite) and from silicon-polyethylene glycol (STPEG-composite) differ in the structure of the silicate phase and its distribution in the composite matrix. Methods of fluorescent and scanning microscopy first confirmed the formation of an organosilica shell around living yeast cells during sol-gel bio-STPEG-composite synthesis. Biosensors based on the yeast cells immobilized in STPEG- and SPEG-composites are characterized by effective operation: the coefficient of sensitivity is 0.85 ± 0.07 mgO2 × min−1 × mmol−1 and 0.87 ± 0.05 mgO2 × min−1 × mmol−1, and the long-term stability is 10 and 15 days, respectively. The encapsulated microbial cells are protected from UV radiation and the toxic action of heavy metal ions. Biofilters based on the developed biocatalysts are characterized by high effectiveness in the utilization of methanol-rich wastewater—their oxidative power reached 900 gO2/(m3 × cycle), and their purification degree was up to 60%.