No abstract

A semi-quantitative method (the enzymatic activity index, EI) and a quantitative method (the amount of reducing sugars, RS) have been used for selecting cellulolytic microorganisms. The analysis was performed with 90 isolates of filamentous fungi selected from pulp mill materials. In both methods 1% low viscosity carboxymethylcellulose (1% CMC l.v.) was used as a substrate. For n = 90, no correlation between the parameters has been found.A further analysis was carried out for 12 selected isolates: 6 with the highest RS values and 6 with the highest EI values. For the chosen fungi, also cultivated on 1% CMC l.v. medium, the following parameters have been determined: the total cellulase activity (filter paper assay, FPase), endoglucanase (CMCase) activity, β -glucosidase (CBase) activity, and the changes in the culture medium viscosity (DV). The statistical analysis revealed a negative, moderately marked correlation between EI and RS and clearly marked positive correlations for two pairs: RS-FPase and DV-FPase. A high positive correlation between RS and DV has also been observed. Correlations between EI, RS, DV, CMCase, and CBase activities were weak. It was shown that the quantitative parameter RS is more suitable than EI for the evaluation of the total cellulolytic activity of filamentous fungi. The application of CMC as the only source of carbon in the culture media and the subsequent determination of EI or RS has failed to provide the means for selecting fungi with a high endoglucanase (CMCase) activity.

Maize attacked by the facultative biotrophic smut pathogen, Ustilago maydis (Basidomycetes) was ensiled in microsilos in two combinations of infected and non-infected plants, with or without biological (Polmasil) or chemical (Kemisile 2000) additives. The silage was subjected to chemical and microbiological analyses. The aerobic stability of the silage was tested. Ustilago maydis constituted up to 6.22% of the total yeast content (CFU g -1 ) in the infected and 0.22% in the noninfected material. Silage made from infected plants had a higher content of fungi (6.45 vs 4.54), moulds (6.20 vs 4.54), and yeast (6.08 vs 3.71) expressed as log 10 CFU g -1 as compared with noninfected plants. The use of the chemical additive decreased these effects. The contents of ochratoxin, zearalenone, and deoxynivalenol were low and did not change during the ensiling. The cytotoxicity test did reveal toxicity of silage from infected plants, however. It seems that the observed toxicity is the effect of toxins other than those assayed.