Several lactic acid bacteria produce exopolysaccharides (EPS), either attached to
the cell wall or excreted into the environment as slime material. EPS produced by
Lactobacillus delbrueckii subsp. bulgaricus (Lb. bulgaricus)
and Streptococcus thermophilus play an important role in improving the texture and stability of yogurt
and preventing syneresis (Cerning, 1990; Nakajima et al. 1990). The amount and
composition of the EPS produced by lactic acid bacteria are dependent on a number
of factors, such as temperature, initial pH, carbon source and the availability of
minerals, vitamins and other medium components.
In previous work it was shown that the production and sugar composition of the
EPS from Lb. bulgaricus NCFB2772 are affected by the carbohydrate source (Grobben
et al. 1995, 1996). In a simplified defined medium, from which several vitamins and
trace elements were omitted, EPS production by Lb. bulgaricus significantly
increased, although growth of the strain was reduced (Grobben et al. 1998).