Faculty of Food Technology and Biotechnology, University of Zagreb
Abstract
A wild fungal strain isolated from soybean oil and identified as Penicillium aurantiogriseum initially presented a volumetric lipase activity of 0.4 U/mL in submerged culture in a medium containing 0.5 % yeast extract and 1 % olive oil. Studies were undertaken to improve lipase production. The effect of nitrogen source was studied by adding casein peptone, meat peptone, yeast extract or ammonium sulfate to a medium containing potassium nitrate and other mineral salts. The best yield, of 13 U/mL after 72 h, was obtained with the medium supplemented with ammonium sulfate. With the ammonium sulfate concentration increased to double the C/N ratio from 2.5 to 5, a lipolytic activity of 18 U/mL was obtained. Olive, corn, soy and sunflower oils were tested as carbon sources in this medium, with olive oil at 1 % giving a lipolytic activity of 25 U/mL after 48 h, the highest yield obtained in this study. Enzyme production was best at 29 °C, within a range tested from 26 to 32 °C. These results are promising because this strain produces lipase in an inexpensive inorganic medium and we succeeded in increasing the lipolytic activity 62-fold over the initial values obtained with the non-optimized medium
