Ribonuclease production by Aspergillus flavipes. A sulphureus and A. fische
ri in semisynthetic medium, after 24-144 hours at 30 degrees C under shakin
g, was studied. After cultivation, the medium was separated from micelia by
filtration and the resultant solution was used as enzymatic extract. The h
ighest amount of biomass and RNase was obtained after 96 hours of cultivati
on. The enzymes produced by three species presented similar characteristics
, with optimum temperature at 55 degrees C and two peaks of activity at pH
4.5 and 7.0. A. flavipes RNases were more sensitive to temperature: 50% of
the initial activity was lost after 1 hour at 70 degrees C. After this heat
treatment, RNase of A. sulphureus lost 30% of this activity and that of A.
fischeri only 16%. The nucleotides released by enzimatic hydrolysis of RNA
were separated by ion exchange chromatography in a AG-1X8-formiate column
and identified by paper chromatography. This procedure indicated that the r
aw enzymatic extract of Aspergillus flavipes is able to hydrolyze RNA, rele
asing 3'-nucleotides monophosphate at pH 4.5 and 3' and 5'-nucleotides mono
phosphate at pH 7.0 and 8.5. This result suggests that this strain produces
two different types of RNase, one acidic and other alcaline, with differen
t specificities.