Résumé:
Protease is one of the enzymes which find wide industrial and
pharmaceutical applications.
Objectives: The soil bacterium Bacillus subtilis (accession number KC341751) was investigated
in the optimization of protease production under different culture conditions. This strain was first,
screened and evaluated for its antifungal activity against Candida albicans, one of the most important
human fungal pathogens.
Methods: The capacity of B. subtilis to produce protease was shown by In vitro assay with the
antagonist and its cell-free culture supernatant, on agar plates. The identification of this strain was then
done based on its morphological as well as biochemical characteristics, later confirmed by 16s rDNA
sequencing and BLAST analysis. Besides, the screening of protease activity by B. subtilis was checked
by growing it on specific agar medium; by spot inoculation method. Moreover, in order to optimize the
production of this enzyme, B. subtilis was grown under different values of pH, Temperature, and diverse
concentrations of glucose.
Results and discussion: The results revealed that B. subtilis inhibited the growth of C.
albicans, by developing a hydrolysis zone of 25 mm. Furthermore, the screening of protease activity
showed a high zone of activity (34 mm) after 24h of incubation at 30°C. In addition, the optimization
of the protease production under various conditions exhibited that the optimal pH and temperature were
7 and 50°C, with a proteolytic activity of 45.24U/ ml and 17.86U/ml respectively. However, the
cultivation of B. Subtilis on different concentrations of glucose showed that the proteolytic activity
increases as a function of the increase of the glucose concentration in the culture medium namely;
13.69U/ml for 0.4% glucose.
Conclusion: These results express that the protease produced in the present study is neutral and
thermostable. The presence of glucose in the medium with pH 7 and temperature 50°C enhanced
enzyme production. Thus, such conditions were able to acts as a promoter for better protease activity;
wich is very interesting in various industries especially pharmaceutical one
