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Exopolysaccharides produced by mixed culture of yeast Rhodotorula rubra GED10 and yogurt bacteria ( Streptococcus thermophilus 13a + Lactobacillus bulgaricus 2‐11)
Author(s) -
Simova E.D.,
Frengova G.I.,
Beshkova D.M.
Publication year - 2004
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1111/j.1365-2672.2004.02316.x
Subject(s) - streptococcus thermophilus , lactose , lactobacillus , yeast , starter , galactose , food science , fermentation , rhodotorula , arabinose , polysaccharide , fermentation starter , xylose , chemistry , biology , bacteria , biochemistry , lactic acid , genetics
Aims: The studies of the production of exopolysaccharides by lactose‐negative yeast and a yogurt starter co‐cultivated in a natural substrate containing lactose may be considered of interest because they reveal the possibilities for high‐efficiency synthesis of biopolymers by mixed cultivation. Methods and Results: The mixed culture Rhodotorula rubra GED10 + ( Streptococcus thermophilus 13a + Lactobacillus bulgaricus 2‐11) was cultivated in cheese whey ultrafiltrate (WU) (44·0 g lactose l −1 ) at initial pH 6·0, 28°C, under intensive aeration (air‐flow rate 1·0 l l −1 min −1 , agitation 220 rev min −1 ) in a MBR AG fermentor. The mixed culture manifested the highest activity for synthesis of exopolysaccharides (19·3 g l −1 ) and cell mass (21·0 g l −1 ) at the 84th hour. The yogurt starter synthesized neutral exopolysaccharides, while the mixed culture yeast + yogurt starter produced acidic exopolysaccharides containing uronic acid (6%). The neutral sugar composition was identified as mannose, glucose, galactose, xylose and arabinose. Mannose dominated in the polymer composition (83%) that was produced only by the yeast (97%). Conclusions: Lactose in the WU can be effectively utilized by a co‐culture of lactose‐negative yeast–yogurt starter for synthesis of exopolysaccharides. Significance and Impact of the Study: The present findings propose an alternative use of WU as a cost‐effective carbohydrate substrate, and suggest that the lactose‐negative yeast Rhodotorula rubra can have industrial application as producers of exopolysaccharides.