IDENTIFICATION AND USE: only three vitamins (pantothenate, p-amino benzoic acid, nicotinic acid) and two amino acids (serine, glutamine) were required in the growth medium for Gluconobacter oxydans which allowed the concentration of yeast extract to be reduced to 5–10% of the previous concentration.

When compared with data from cultivations with complex media, the new medium gave a lower yield (about 0.02 g biomass per g glycerol) and comparable growth rate (0.24 to 0.38 h−1) but a higher productivity (10.3 g dihydroxyacetone/gh).

A semisynthetic medium, containing yeast extract as the only non defined component and glucose, glycerol, Tween 80 and mineral salts, has been developed to grow the strains of Propionibacterium acnes Beck 2037, Gerrath 2038 and Vogel 2039, at a rate comparable to that of complex media.

An average of 10(12) cells per 1 (equivalent to approximately 1.5 g/l dry weight) was usually achieved. These yields are appropriated for biochemical and immunological studies, e.g. cell wall preparation, polysaccharides isolation, etc. In this work, some properties of the cell walls (sugar and amino acid composition) and the antigenic polysaccharides (neutral and amino sugar components) are described.