Composition of extracellular polymeric substances produced by Geotrichum sp. J-5

Abstract

A fungus strain (J-5) which produces flocculating substances was isolated from activated sludge and identified as Geotrichum candidum. The growth of the isolated Geotrichum candidum was maximal after 3 days cultivation while the highest flocculating activity of the culture broth was highest after 1 day cultivation. The results of flocculating activity for Geotrichum candidum showed that the active ingredient of bioflocculant was existed in the supernatant of free-cell. The crude bioflocculant could be recovered from the supernatant of the culture broth by ethanol precipitation and dialysis against deionized water. The polymer was identified to be polysaccharide containing neutral sugar and uronic acid as its major and minor components, respectively. Infrared spectra showed the presence of hydroxyl, carboxyl and methoxyl groups in its molecules which could flocculate by bridging.