Effect of culture conditions on lipase production by Fusarium solani in batch fermentation.

Lipase (Glycerol ester hydrolase EC 3.1.1.3.) from a Brazilian strain of Fusarium solani FSI has been investigated. The effect of different carbon sources and trace elements added to basal medium was observed with the aim of improving enzyme production. Lipase specific activity was highest (0.45 U mg(-1)) for sesame oil. When this medium was supplemented with trace elements using olive oil, corn oil and sesame oil the lipase specific activity increased to 0.86, 1.89 and 1.64 U mg(-1), respectively, after 96 h cultivation without any considerable biomass increase. The Km of this lipase using pNPP (p-nitrophenylpalmitate) as substrate, was 1.8 mM with a Vmax of 1.7 micromol min(-1) mg protein(-1). Lipase activity increased in the presence of increasing concentrations of hexane and toluene. In contrast, incubation of this enzyme with water-soluble solvents decreased its activity after 10% concentration (v/v) of the solvent. The lipase activity was stable below 35 degrees C but above this temperature activity losses were observed.

Lipase from a Brazilian strain of Penicillium citrinum.

A lipases (glycerol ester hydrolases E. C. 3.1.1.3) from a brazilian strain of Penicillium citrinum has been investigated. When the microorganism was cultured in the simple medium (1.0% olive oil and 0.5% yeast extract), using olive oil in as carbon source in the inocula, the enzyme extracted showed maximum activity (409 IU/mL). In addition, decrease of yeast extract concentration also reduces the lipase activity. Nevertheless, when yeast extract was replaced by ammonium sulfate, no activity was detected. Purification by precipitation with ammonium sulfate showed best activity in the 40-60% fraction. The optimum temperature for enzyme activity was found in the range of 34-37 degrees C. However, after 30 min at 60 degrees C, the enzyme was completely inactivated. The enzyme showed optimum at pH 8.0. The dried concentrated fraction (after dialysis and lyophilization) maintained its lipase activity at room temperature (28 degrees C) for 8 mo. This result in lipase stability suggests an application of lipases from P. citrinum in detergents and other products that require a high stability at room temperature.

Effects of potassium on the ethanol production rate of Saccharomyces cerevisiae carrying the plasmid pCYG4 related with ammonia assimilation.

The influence of potassium on ethanol production by Saccharomyces cerevisiae wild type and AR5 cells carrying the plasmid pCYG4 was investigated. This plasmid carries the glutamate dehydrogenase gene conferring an 11-fold higher level of expressed enzyme activity over the wild type cells. All experiments were carried out in batch culture with medium supplemented to different potassium concentrations up to 180 mM. Maximum ethanol production rate was observed in the AR5 cells grown in medium supplemented with 3.5 mM of potassium ions. Glucose uptake rate increased with increasing potassium up to 60 mM, but higher concentrations depressed glucose uptake rate in both strains. Furthermore, the wild type cells showed higher growth rate, ethanol production, and glucose consumption rate than the AR5 cells. These lower rates in the AR5 cells could be explained by repression of potassium uptake by an enhancement of ammonium feeding, and greater energy requirements by these cells due the presence of the plasmid.