The ciliates purified and incubated with antibiotics as described above were sedimented and the sediment was collected and suspended in the warm salt solution of “Hungate” (Table 2). Finally the new portions of antibiotics were added and the 50 ml samples of well mixed suspension of ciliates were transferred to the Erlenmeyer flasks 100 ml of volume and incubated for 12 h under continuous flow of CO2. They were incubated alone (control) or in the presence of 50 mg of lyophilized fungal zoospores (experimental cultures). The cultures of accompanied bacteria were obtained by filtration of the suspension of protozoa through a screen of pore size 40 μm. The filtrate was collected and poured to the Erlenmeyer flask of the same volume (see above) as well as incubated simultaneously with the cultures of ciliates in presence of the same doses of lyophilized fungal zoospores. The fermentation experiment was repeated three times on three different days. The samples to determine the concentration of volatile fatty acids and ciliate number were taken at the beginning of incubation period and at 3, 6, 9 and 12 h thereafter. They were fixed with formic acid in the proportion of 10% v:v or with 4% formalin solution (1:1; v:v), respectively. The concentration of VFA was measured by gas chromatography method according to Ziołecki and Kwiatkowska [32] using the Philips PU 4410 gas chromatograph. Ciliates were counted under a light microscope [17].