Abstract

Some microorganisms such as yeasts can produce high molecular weight and valuable polymers that known as exopolysaccharides (EPSs). Given the functional properties of yeast exopolysaccharides (EPSs) and a few numbers of studies in this field, the present study was aimed to characterize the EPSs from Rhodotorula minuta (IBRC-M 30135) and to evaluate their emulsifying, antioxidant and antiproliferative activities. R.minuta excreted 1.2 +/- 0.1 g of the EPSs per 1000 ml of fermentation medium. Glucose, mannose and rhamnose were found as main monosaccharides of the EPSs (49, 38 and 13 mol, respectively) through gas chromatography-mass spectrometry (GC-MS) analysis. In addition, three EPS fractions were obtained with the molecular weights of 356, 500 and 220 kDa. The water retention capacity of the EPSs was 342 +/- 27. The EPSs exhibited relatively good oil-emulsifying activity and the enhanced synergism between the R.minuta's EPSs and commercially used hydrocolloids (guar gum and sodium alginate) was observed. In vitro, antioxidant activity was investigated against DPPH, hydroxyl and superoxide free radicals. At a concentration of 10 mg/ml, the DPPH, hydroxyl and superoxide free radicals scavenging activities were 21.8 +/- 0.7, 24.6 +/- 1.4 and 12.1 +/- 0.4, respectively; and the scavenging activities against all were higher than hyaluronic acid. In addition, the treatment of human breast adenocarcinoma (MCF7) and Madin-Darby Canine Kidney (MDCK) cell lines with 20-1000 mu g/ml of the EPSs caused no significant differences in the cells proliferation (P>0.05). These results indicated the promising potential of the EPSs from R.minuta as non-toxic and biocompatible compounds for using in food, cosmetic and pharmaceutical fields.