“3-in-1” Hybrid Biocatalysts: Association of Yeast Cells Immobilized in a Sol–Gel Matrix for Determining Sewage Pollution

This study presents a novel ″3-in-1″ hybrid biocatalyst design that combines the individual efficiency of microorganisms while avoiding negative interactions between them. Yeast cells of Ogataea polymorpha VKM Y-2559, Blastobotrys adeninivorans VKM Y-2677, and Debaryomyces hansenii VKM Y-2482 were immobilized in an organosilicon material by using the sol–gel method, resulting in a hybrid biocatalyst. The catalytic activity of the immobilized microorganism mixture was evaluated by employing it as the bioreceptor element of a biosensor. Optical and scanning electron microscopies were used to examine the morphology of the biohybrid material. Elemental distribution analysis confirmed the encapsulation of yeast cells in a matrix composed of methyltriethoxysilane (MTES) and tetraethoxysilane (TEOS) (85 and 15 vol %, respectively). The resulting heterogeneous biocatalyst exhibited excellent performance in determining the biochemical oxygen demand (BOD) index in real surface water samples, with a sensitivity coefficient of 50 ± 3 × 10–3·min–1, a concentration range of 0.3–31 mg/L, long-term stability for 25 days, and a relative standard deviation of 3.8%. These findings demonstrate the potential of the developed hybrid biocatalyst for effective pollution monitoring and wastewater treatment applications.