Synthesis of Mannose-Rich Exopolysaccharide by Rhodotorula glutinis 16P Co-Cultured with Yeast or Bacteria

Exopolysaccharides from the lactose-negative yeast Rhodotorula glutinis 16P were synthe­ sized by co-cultivation with the yeast Kluyveromyces lactis MP11 or with the homofermentative lactic acid bacteria Lactobacillus helveticus 9A in a cheese whey ultrafiltrate. Exopoly­ saccharides were produced by lactose hydrolysis, performed by two pathways: with ß-galactosidase from Kluyveromyces lactis MP11 which assimilates glucose and galactose; with ß-galactosidase and Lactobacillus helveticus 9A which uses lactic acid. By growing the two mixed cultures maximum yield was obtained as follows: 11.4 g/1 and 15.8 g/1, respectively. Structural units of the carbohydrate composition of the two polymers are mannose (7 2 .4 63.5% ), glucose (2 .0 -1 5 .9 % ), galactose (2 5 .3 -1 9 .8 % ) and xylose (3 .6 -4 .3 % ). Mannose dominated in the polysaccharide compositions.