Among 97 fungal strains isolated from soil collected in the arctic tundra (Spitsbergen), Penicillium chrysogenum 9' was found to be the best lipase producer. The maximum lipase activity was 68 units mL(-1) culture medium on the fifth day of incubation at pH 6.0 and 20 degrees C. Therefore, P. chrysogenum 9' was classified as a psychrotrophic microorganism. The non-specific extracellular lipase showed a maximum activity at 30 degrees C and pH 5.0 for natural oils or at pH 7.0 for synthetic substrates. Tributyrin was found to be the best substrate for lipase, among those tested. The Km and Vmax were calculated to be 2.33 mM and 22.1 units mL(-1), respectively, with tributyrin as substrate. The enzyme was inhibited more by EDTA than by phenylmethylsulfonyl fluoride and was reactivated by Ca2+. The P. chrysogenum 9' lipase was very stable in the presence of hexane and 1,4-dioxane at a concentration of 50%, whereas it was unstable in presence of xylene.

A novel method for increasing dissolved oxygen concentration in culture media has been developed. It involves adding hydrogen peroxide (H 2 O 2 ) to the medium which is then decomposed to oxygen and water by catalase. Some factors affecting oxygenation of culture were investigated. Maximal oxygen concentration occurred in 50 ml of the medium containing 0Á2 g wet mycelium and 0Á2% glucose at pH 5Á0. A new apparatus for automated addition of H 2 O 2 to the bioreactor to keep the dissolved oxygen concentration constant over the range 1±100% 2% was tested. A signi®cant increase (over sixfold) of intracellular catalase activity was obtained while the dissolved oxygen concentration remained stable (30% 2%).

The total of 98 strains of moulds were isolated from soils collected in arctic tundra (Spitzbergen). Among these strains Penicillium cyclopium 1, the most effective for production of catalase, was selected by the method of test-tube microculture. The time course of growth and catalase production by this strain showed the intracellular activity of this enzyme to be about 3-fold higher than its extracellular level Some properties of crude catalase preparation, isolated from postculture liquids by lyophilization, were also examined. Catalase activity showed its maximum at 15 degrees C, indicating adaptation of the enzyme to lower temperatures of the arctic environment.

The production of extracellular catalase in a submerged culture by a number of biochemical mutants has been evaluated. Eight of these mutants showed increased extracellular catalase, the level of which ranged widely in individual cases from 44% to over 94% in comparison with the parental strain. Studies of the relationship between a criterion of selection and the frequency of mutation showed that the highest frequency of positive mutations (15.8% and 24.2%) was obtained with respect to mutants resistant to ethidium bromide (1 mmol/l) and sodium gluconate (45%) respectively. The time course of growth and enzyme production by the most active mutant, AM-20, showed extra- and intracellular catalase activities increasing about 2- and 2.6-fold respectively, compared with the parental strain.

A total of 24 yeast strains were tested for their capacity to produce ethanol, and of these, 8 were characterized by the best ethanol yields (73.11-8 1.78%). The most active mutant Saccharomyce s cerevisiae ER-A, resistant to ethanol stress, was characterized by high resistance to acidic (pH 1.0 and 2.0), oxidative (1 and 2% of H2O2), and high temperature (45 and 52 degrees C) stresses. During cultivation under all stress conditions, the mutants showed a considerably increased viability ranging widely from about 1.04 to 3.94-fold in comparison with the parent strain S. cerevisiae ER. At an initial sucrose concentration of 150 g/l in basal medium A containing yeast extract and mineral salts, at 300C and within 72 h, the most active strain, S. cerevisiae ER-A, reached an ethanol concentration of 80 g/1, ethanol productivity of 1.1 g/Il/h, and an ethanol yield (% of theoretical) of 99.13. Those values were significantly higher in comparison with parent strain (ethanol concentration 71 g/1 and productivity of 0,99 g/l/h). The present study seems to confirm the high effectiveness of selection of ethanol-resistant yeast strains by adaptation to high ethanol concentrations, for increased ethanol production.