Potential use of lemongrass essential oil as fungicide against Aspergillus brasiliensis and as post-harvest protectant of wheat

Fungi are among the main responsible for damage and loss in stored grains, its control has been done through synthetic substances, which are harmful to man and the environment. Brazil, one of the leading countries in agriculture, has optimal environmental conditions for the development of mycotoxigenic fungi. Most of the synthetic chemicals used as preservatives have often been realized to be toxic to humans and also cause adverse environmental effects. Thus, it is necessary to search for alternative methods of controlling. In this study the aimed was to evaluate the efficacy of lemongrass essential oil in the control of the Aspergillus brasiliensis. In vitro and serial microdilution tests were carried out at different concentrations of essential oil and citral, which corresponds to 72% of the total oil composition. Inhibition of fungal growth on contaminated wheat grain was evaluated. The in vitro test results showed that the essential oil has fungicidal potential at concentrations from 0.6 956;L mL-1, the minimum inhibitory concentration was determined at 0.8 956;L mL-1. The tests with citral showed fungal control at concentrations from 0.6 956;L mL-1 onwards. For wheat grain, fungal growth inhibition was obtained at the concentration of 1.6 956;L mL-1. The essential oil of Cymbopogon flexuosus showed fungicidal activity against the fungus Aspergillus brasiliensis.

Culture conditions for the production of thermostable amylase by Bacillus sp

Studies on the alfa-amylase production were carried out with a bacterial strain isolated from a soil sample. The cells were cultivated in a mineral medium containing soluble starch as sole carbon source. The addition of calcium (10 mM) or peptone 1(per cent) and yeast extract 0.5(per cent) to the mineral medium shortened the lag period and improved the growth and alfa-amylase synthesis. The addition of glucose to the culture diminished greatly the synthesis of alfa-amylase, demonstrating that a classical glucose effect is operative in this organism. The optimum temperature and initial medium pH for amylase synthesis by the organism were 50ºC and 7.0 respectively. The optimal pH and temperature for activity were 6.0 and 50ºC respectively. The enzyme extract retained 100 per cent activity when incubated for one hour at 90ºC and 40(per cent) at 60ºC for 24 h. The addition of glucose to the culture diminished greatly the synthesis of alfa-amylase.