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Cultures of the fungal strain Humicola lutea 110 were grown in a 3-l bioreactor. Effects of dissolved oxygen concentration (DO) on cell growth, intracellular protein content and antioxidant enzyme activities (SOD and catalase) were investigated. Controlling DO from 20 to 60% lead to: (I). The lethal phase of growth was reached faster; (ii) strong reduction of the intracellular protein content, and (iii) increase of antioxidant enzyme activities. The most efficient SOD biosynthesis was achieved at the 1st maximum of activity in the culture grown under DO uncontrolled conditions.

SunimaryThe optimal parameters for the cultivation in 10-1 fermenters of a mutant strain Humiwla lutea 120-5 were established: temperature 30°C, inoculum size 6%, inoculum age 24 h, aeration rate 0,6 vol/vol . min, medium agitation 620 rpm and cultivation time 72 h. A maximal proteolytic activity of 2000 pg tyrosine liberated from 2% casein ml-l culture filtrate min-l at pH 3.0 and 4OoC was obtained under the fixed conditions. a-Amylase biosynthesis during the Cultivation of EI. lutea 120-5 was observed but it was insignificant to the 72nd h. It is. demonstrated that starch can be used as alternative to glucose carbon source. It is proved that the mutant strain

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