Screening for siderophore production from tropical isolates of Aureobasidium pullulans

Aureobasidium pullulans, generally known as a black yeast, can produce a wide range of valuable products, including siderophore which is an iron chelating agent that secreted for iron uptake. This compound can be used as a medical agent to treat haemophiliac patients. In addition, some siderophores were reported to have an antitumor activity. In this research, a number of tropical A. pullulans isolates were screened for siderophore production using ferric perchlorate assay. They were cultivated in the iron-depleted liquid medium at room temperature with 200-rpm agitation for 5 days. The supernatants were harvested by centrifugation and measured for siderophore level. The results showed that all 73 isolates of A. pullulans could produce siderophores in a range of 0.037-0.550 mg/mL and were divided into 3 groups: high (> 0.40 mg/mL), moderate (0.20-0.40 mg/mL), and low (< 0.20 mg/mL) productivity. VK02, the highest siderophore-producing isolate, was selected for enhancing siderophore production. Under the optimal condition, this isolate produced 0.745 g/L of the siderophore. Furthermore, the produced siderophores will be purified, characterised and tested for the antitumor and antimicrobial activities.