Exopolysaccharide production by LactobaciUlus casei CGll was studied in basal minimum medium containing various carbon sources (galactose, glucose, lactose, sucrose, maltose, melibiose) at concentrations of 2, 5, 10, and 20 g/liter. L. casei CGll produced exopolysaccharides in basal minimum medium containing each of the sugars tested; lactose and galactose were the poorest carbon sources, and glucose was by far the most efficient carbon source. Sugar concentrations had a marked eflect on polymer yield. Plasmid-cured Mucderivatives grew better in the presence of glucose and attained slightly higher populations than the wild-type strain. The values obtained with lactose were considerably lower for both growth and exopolysaccharide yield. The level of specific polymer production per cell obtained with glucose was distinctively lower for Mucderivatives than for the Muc+ strain. The polymer produced by L. casei CGll in the presence of glucose was different from that formed in the presence of lactose. The polysaccharide produced by L. casei CGII in basal minimum medium containing 20 g of glucose per liter had an intrinsic viscosity of 1.13 dl/g. It was rich in glucose (76%), which was present mostly as 2or 3-linked residues along with some 2,3 doubly substituted glucose units, and in rhamnose (21%), which was present as 2-linked or terminal rhamnose; traces of mannose and galactose were also present.

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The growth of bacteria normally used to produce yoghurt was compared in soymilk and cow milk. Whether or not Bifidobnc&ium ssp. was present, fermented soymilks [soyoghurt (S), soyoghurt f bifidobacteria (SB)] were less acidic than fermented cow milks [yoghurt (Y), yoghurt + bifidobacteria (YB)]. When bifidobacteria were present (in SB), streptococci were more numerous than lactobacilli. Bifidobacteria in YB stimulated maximal growth of both yoghurt bacteria. In comparison to nonfermented milks, acetaldehyde and diacetyl increased in all cultures. Ethanol increased only in S/SB and acetone was detected only in Y/YB. Quantities of volatile products in Y/'YB were slightly lower than those in Y/S. In all cultures, n-hexanal was almost totally absent.

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