The pectin lyase (PL 4.2.2.10) (4) activity of Penicillium sp. 25/5B on beet-pulp water extracts, supplemented with nitrogen salts was studied. The highest PL activity and biomass production was obtained on a 4% beet-pulp water extract supplemented with (NH₄)2HPO₄ and additionally buffered with a phosphate buffer, pH=6.0 (Fig. 3).