The photocatalytic activity of nanocomposites based on theta-modification of aluminum oxide Al2O3 with different TiO2 content for heterogeneous photocatalysis and biodegradation of pathogenic microorganisms under the action of LED radiation with a wavelength of 405 nm has been studied. It was found that all the investigated nanocomposites have photocatalytic activity. The maximum antibacterial efficiency of composites with a TiO2 content of 8 wt% (reduction of CFU of Staphylococcus aureus 209 P to 86%), which allows us to recommend this nanomaterial as a promising antimicrobial coating.