Studies on environmental and nutritional factors on production of antifungal substance by Lactobacillus acidophilus R.

Abstract

The optimal incubation temperature and period for the maximal production (27 units ml −1) of antifungal substance (AFS) by Lactobacillus acidophilus R. in Elliker's broth was 30°C and 48 h. Prolonged incubation led to diminished activity. The pH optima for the production of AFS ranged from 6·8 to 7·6, at which 24·16 units ml −1. of AFS were produced. Although incorporation o f yeast extract in the growth medium was stimulatory at 1·0%, beef extract and casamino acid stimulated AFS production at the level of 1·5%. Tryptone, on the other hand, was stimulatory at the level of 2·0%. Similarly, addition of glucose to the basal medium at the level of 0·5–1·0% enhanced the production of AFS (29 units ml −1). Beyond 2·0% it was inhibitory. There was an appreciable increase in production of AFS with the concomitant increase (0·5–3·5%) in the salt concentration in the growth medium. Calcium chloride was also stimulatory at the 0·1 % level, at which AFS production increased to 35 units ml −1. However, further increase in the calcium concentration was inhibitory. Contrary to this, magnesium chloride and manganese sulphate were stimulatory at low levels (0·02 and 0·005%, respectively).