spherical biocatalyst particles having increased abrasion resistance are obtained containing a biologically active material such as a microorganism , tio 2 particles having a size of 0 . 1 to 1 micrometer and an ionotropic biopolymer such as alginate , pectin , carrageenan or chitosan . the biocatalyst is prepared by forming a homogeneous degassed aqueous dispersion containing the biopolymer , 0 . 1 to 20 % by weight of the biologically active material and 7 to 35 % by weight of the tio 2 particles , and dropping droplets of the dispersion from a nozzle into a precipitation both containing polyvalent cations to precipitate the biopolymer and form spherical biocatalyst particles of 0 . 05 to 5 mm in diameter . the droplets may pass through a gas space containing an inert gas , air or reactive vapors such as acetaldehyde before reaching the precipitation bath . the tio 2 particles may be surface - impregnated with al 2 o 3 and / or aluminum oxide hydrate .