Production d’alpha amylase par des moisissures cultivées sur milieu à base de rebuts de dattes.

Abstract

In Algeria, significant amounts of date rejects are generated with each harvest. These date rejects, rich in fermentable sugars, rock salt and vitamins can be a medium favorable as well for the development of the micro-organisms as for the production of the metabolites to strong added value such as the amylolytic enzymes, in particular l'α-amylase. With an aim of selecting new producing moulds d'α-amylase and of optimizing a culture medium containing date rejects, five moulds of which Rhizopus sp1., Rhizopus sp2. Penicillium sp1., Alternaria sp. and Helminthosporium sp. were isolated starting from the grains from barley and were cultivated on date must for the production of this enzyme by submerged fermentation. The kinetics of production of biomass and α-amylase was studied while being based on the daily calculation of the biomass and the proportioning of the enzymatic activity by the method of Bernfeld. In order to improve considerably the development of these moulds and the d'α-amylase production, the basic medium was enriched by various sources carbon, nitrogen and by phosphorus, and was optimized by using a statistical method of experimental planning (matrices of Plackett-Burmun). Our results showed that the biomass appears as of the first hours of incubation and reached its maximum at 72 hours for the strains of Rhizopus sp. (1 and 2), Alternaria sp. and Helminthosporium sp. and to 96 H for the strains of Penicillium sp., whereas the secretion of the enzyme begins only at 48 hours to reach its maximum at 72 hours for the strains of Rhizopus sp. (1 and 2) and at 96 hours for the stocks Penicillium sp., Alternaria sp. and Helminthosporium sp. The statistical analysis allowed the selection of the yeast extract, the starch, the KH2PO4, urea and the temperature like factors positively influencing the production of biomass by all the strains, and the yeast extract like the most influential factor positively on the α-amylase production by the five strains, compared to the factors: pH, temperature, starch, urea and KH2PO4 whose influence varies from one strain to another.