Enhancement of exopolysaccharide production by lactobacillus delbrueckii subsp. bulgaricus NCFB 2772 with a simplified defined medium - Boels, I. C.; Boer, F.; Chin-Joe, I.; De Bont, J. A. M.; Grobben, G. J.; Kitzen, V. A.; Sikkema, J.; Smith, M. R.