IMMOBILIZATION OF MICROORGANISMS ON SOLID SORBENTS OF A NEW GENERATION OBTAINED ON THE BASIS OF ALUMINUM OXIDE VIA MICRO-ARC OXIDATION

Abstract

This study presents experimental data on the sorption of microorganisms onto composite ceramic coatings formed on aluminum alloys (Zn–Al, Al–Mg6, and D16) via micro-arc oxidation (MAO). The tested microorganisms included Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Staphylococcus aureus, the yeast-like fungus Candida albicans, and the micromycete Aspergillus niger. The results demonstrated that the sorption capacity of the coatings is strongly influenced by microbial species, as well as by the chemical composition and surface morphology of the sorbents. Scanning electron microscopy (SEM) revealed a heterogeneous distribution of adsorbed cells and spores, governed by microporosity, phase composition (oxides of aluminum, magnesium, zinc, and silicon), and surface structural features. The maximum sorption of E. coli on the Zn–Al coating reached 0.9 × 10⁶ cells/mm² at an concentration of 3 × 10⁸ cells/mL, exceeding that observed on the D16 alloy by 30%. Comparable trends were observed for P. aeruginosa and B. subtilis. Coccoid cells of S. aureus also exhibited efficient adsorption, with densities of 1.80 × 10⁶ cells/mm² on Zn–Al, 1.50 × 10⁶ cells/mm² on D16, and 1.30 × 10⁶ cells/mm² on Al–Mg6 surfaces. At higher microbial concentrations (≥ 3 × 10⁸ cells·cm⁻³), the maximum surface sorption density reached 7.0–8.0 × 10⁵ cells/mm². Yeast cells of C. albicans and spores of A. niger exhibited adsorption behavior similar to that of S. aureus. The highest sorption capacity was consistently observed for Zn–Al coatings, followed by D16, while lower values were recorded for Al–Mg6 and control samples. Overall, MAO-derived composite coatings demonstrated high porosity and significant sorption capacity, indicating their strong potential as adsorbents and carrier materials in industrial microbiology, biotechnology, and environmental monitoring. Furthermore, these coatings represent promising candidates for future investigations of antimicrobial and anticorrosion properties.