EXOPOLYSACCHARIDE PRODUCTION BY BIFIDOBACTERIUM-LONGUM BB-79

Bifidobacterium longum BB-79 produced an acidic extracellular polysaccharide (EPS), especially when grown on solid medium. The EPS was isolated by ethanol precipitation followed by dialysis and lyophilization. Anion exchange and gel-filtration chromatography were used to further purify and characterize the EPS. The average molecular weight was greater than 200 kDa as estimated by chromatography. Based on gas-liquid chromatography (GLC) and GLC-mass spectrometry analyses, the EPS appears to be composed of galactose and an unidentified hexose (possibly glucose) with a carboxyethyl (lactic acid) substituent. Lactose, when used as the primary carbon source in liquid media, gave the highest yield of EPS. Incubation times longer than 24 h and the initial culture pH (pH 6.0-9.0) had little effect on the amount of EPS produced.