Abstract
Growth supporting abilities of yeast extract-glucose broth prepared from various commercial yeast extract samples for L. blugaricus were compared.
There were considerable differences in the growth supporting ability among the lots of yeast extracts and in some cases, only very poor growth was obtained. It was considered that in these media, some of the growth factors reported in the preceding paper were insufficient to obtain normal growth.
Additions of “tween 80” and panthetine markedly improved the growth and heavy growth was obtained irrespective of the quality of yeast extract used.
Pantethine could be replaced with 0.01 per cent of cysteine. An explanation for this result is, as discussed in the preceding paper, that pantothenic acid which is present in yeast extract medium shows some pantethine activity only in the presence of relatively large amount of cysteine.
At first, the nature of “tween 80” active substance (s) in yeast extract was considered to be phospholipid (s) such as lecithin, since egg lecithin supported growth when added in place of “tween 80”. However, this substance (s) could not be extracted with 95 per cent ethanol and ethanol-ether mixture.
