Exopolysaccharide production in a whey based medium by Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus in pure cultural and in association

Growth and exopolysaccharide (EPS) production by Streptococcus thermophilus SY and Lactobacillus delbrueckii subsp. bulgaricus NCFB 2772 in pure culture or in association were studied during batch fermentations at controlled pH (6.0) in a deproteinized whey based substrate at 37, 40 and 45 degrees C. EPS production was growth-associated for both species. Optimal temperature for EPS production by Str. thermophilus SY was 37 degrees C, with a maximum production of 216 mg/l after 8 h of incubation. Optimal temperature for EPS production by Lb. delbrueckii subsp. bulgaricus NCFB 2772 was 40 degrees C, with a maximum production of 120 mg/l after 3 h of incubation. Growth in association did not result in an increased EPS production. In mixed cultures, the maximum EPS concentration (220 mg/l) was obtained after 8 h at 40 degrees C.