Ribonuclease production by Aspergillus species

Ribonuclease production by Aspergillus flavipes, A. sulphureus And A. fischeri in semisynthetic medium, after 24-144 hours at 30§C under shaking, was studied. After cultivation, the medium was separated from micelia by filtration and the resultant solution was used as enzymatic extract. The highest amount of biomass and RNase was obtained after 96 hours of cultivation. The enzymes produced by three species presented similar characteristics, with optimum temperature at 55§C and two peaks of activity at pH 4.5 and 7.0. A. flavipes RNases were more sensitive to temperatue: 50(per cent) of the initial activity was lost after 1 hour at 70§C. After this heat treatment, RNase of A. sulphureus lost 30(per cent) of this activity and that of A. fischeri only 16(per cent). 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 raw enzymatic extract of Aspergillus flavipes is able to hydrolyze RNA, releasing 3'-nucleotides monophosphate at pH 4.5 and 3'and 5'-nucleotides monophosphate 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 different specificities

Effect of lecithin and soy oil on the ferment ative performance of Saccharomyces uvarum I Z 1904

A proposta deste trabalho foi estudar os efeitos da lecitina e do óleo de soja sobre o desempenho fermentativo de Sacharomyces uvarum I Z 1904, levedura utilizada para produçäo industrial de etanol. High Test Molasses (HTM) foi escolhido como meio de fermentaçäo por ser um substrato pobre em nutrientes, e permitir distinguir a açäo dos lipídios por análise de superfície de resposta mostrou que os lipídios favoreceram o desempenho da levedura principalmente quando aplicados separadamente. Máximas concentraçöes das duas fontes de lipídios no meio estimularam o brotamento mas näo se constituíram em proteçäo contra a morte celular. Considerando a açäo dos lipídios sobre os parâmetors celulares estudados, a suplementaçäo do meio com 3,0g/l de óleo de soja permitiu obter máximas respostas de viabilidade celular, taxa de brotamento e viabilidade dos brotos após 6 ciclos sucessivos