Optimization of medium and cultivation conditions for alkaline protease production by the marine yeast Aureobasidium pullulans

A yeast strain, Aureobasidium pullulans, which could produce the high yield of protease was isolated from sediment of saltern in Qingdao, China. Maximum production of enzyme (623.1 U/mg protein; 7.2 U/ml) was obtained in a medium containing 2.5 g soluble starch and 2.0 g NaNO3, 100 ml seawater, initial pH 6.0, after fermentation at 24.5 °C for 30 h. The protease had the highest activity at pH 9.0 and 45 °C.