CONICET | Buscador de Institutos y Recursos Humanos

Lipase catalyzes hydrolysis and synthesis of compounds with industrial and academic interest. However lipase use is often limited by substrate and product solubility in water systems, and heterogeneous biocatalysis in pure organic solvents by enzyme deactivation, diffusion limitations, etc. Homogenous organic-water systems could improve lipase biotransformations. The aim of this work was the isolation of bacteria which produce organic solvent resistant lipase at high temperatures. Lipolytic thermoresistant microorganisms were isolated from natural sources in tributyrin agar at 55 °C. On the basis of lipolytic activity four strains were selected. These strains were cultured in synthetic liquid medium supplemented with isoamyl alcohol. Strain named S86 was selected based on high cell-free lipolytic activity. Morphological analysis using international criteria allowed to classify strain S86 into Bacillus genera. Fermentation of carbohydrates antibiotic sensitivity test classify the strain into the subtilis group. Lipase production in synthetic liquid medium bath cultures was maximal in the stationary phase. Three times enhanced enzyme production in batch cultures at 55 °C was found in presence of 0,4 % isoamyl alcohol. Analysis of crude enzyme and partially purified extracts using p-nitro-derivates substrates from acetate to stearate displayed abroad specificity. Optimum temperature enzyme activity was found near 65 °C. Homogeneous biocatalysis in 50 % hydrophilic organic solvent concentration displayed enzymatic activities higher than 50 % in glycerol, ethanol, and isopropanol compared to pure buffer system. These results allowed to infer that lipase produced by Bacillus sp. S86 should be usable for biotransformations in homogenous organic-aqueous solvent mxtures. References Baigorí MD, Castro GR, Siñeriz F (1996), Biotech. Appl. Biochem. 24,7. Castro GR (1999), Ezime Microb. Technol. 25, 689.

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