Each 21 selected active D. hansenii was inoculated on Yeast Morphology Broth (YMB: 1% (w/v) glucose, 0.3% (w/v) yeast extract, 0.3% (w/v) malt extract and 0.5% (w/v) proteose peptone). After 120 h of incubation at 20 C, cultures were centrifuged at 2630 g for 15 min. The resultant cell-free supernatant was filtered through a 0.22 mm-pore-size membrane (GE Healthcare Europe GmbH, Freiburg, Germany).