Résumé:
The isolation of yeasts realized on saharian soil from Biskra , allowed to index 5 strains .
They were tested on PDA medium with 1% of starch . On 5 strains , one (S5), presented a
high amylolytic activity compared to the others . The microscopic, physiological and
biochemical studies of this strain , allowed to identify its kind : Lipomyces.
In addition, culture medium , based on flour date rejects, was used at 1.5% for the production
of α-amylase with fermentation of selected yeast Lipomyces sp. The ammonium sulphate (at
0.2%) and yeast extract (at 0.5%) were added respectively as source of nitrogen and
growth factors, with starch at 1% as inductive substrate, in order to constitute a favourable
medium to yeast development and production of α-amylase. The kinetic study for
production of α-amylase realized on this medium, revealed that the production reached its
maximum (6582 U ) at 78 hour of fermentation. Partial purification of enzyme by
ammonium sulphate, gave a maximum yield in enzyme (77.3%) for the fraction 50% . The α-
amylase partially purified, has an optimal pH of 6 and an optimal temperature of 55°C. The
study of the thermostability of α-amylase of Lipomyces sp, revealed that enzyme is
thermostable. The half-life of the enzyme at 80°C, is of 150 min and at 90°C, it is of 130
min .
