Publications Scientifiques

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Author: search.filters.author.Belbraouet, S.

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    Valorisationof microbial biodiversity : Characterization of a milk-clotting enzyme produced byBacillus velezensis FK6Astrain isolated from Algerian dairy farm soil in light of its usein the manufacture of hard cooked cheeses
    (2021) Boumediene, F.; Talantikite, S.; Haddad, S.; Nouani, A.; Triki, S.; Belbraouet, S.
    A strain known as FK6A, which produces a milk-clotting enzyme isolated from the soil of an Algerian dairy factory, was identified as Bacillus velezensis based on morphology and internal transcription spacer sequence. Phylogenetic and sequencing analysis of 16S rDNA gene showed a 100% identity match between the tested strainand the Bacillusvelezensis in the database (Code MH368142). This strain produced an active extracellular protease purified by partial purification using ammonium sulfate fractionation(40–80% saturation) followed by chromatography of molecular exclusion, which revealed the existence of tow active peaks. The optimal activity was observed at pH 5.7; 75°C and 40 mM of CaCl2. The clotting enzyme has been shown to be a metalloprotease inhibited by EDTA. The highly proteolytic activity of the Bacillus velezensis extracts observed on the curds appears a few minutes after the appearance of a firm coagulum reflected by the appearance of an abundant serum.Thus, to solve this problem and to inhibit proteolytic activity, the curds were cooked after brewing during the manufacturing process
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    Purification and characterization of a milk-clotting protease from Mucor pusillus : method comparison
    (Academic Journals, 2011) Nouani, A.; Moulti-Mati, F.; Belbraouet, S.; Bellal, M.M.
    Crude enzymatic extract obtained from five fermentations (300 g of wheat bran) was characterized by a clotting activity of 0.34 ± 0.08 UP/ml with a strength ratio of 1/1: 200. The comparative study of the summaries from 2 purification protocols showed that it is possible to recover 6% of the initial proteins with a 44.54% activity after gel filtration (protocol I), which appeared more technically sound when compared to ion-exchange (1.80% of total proteins with a 23% performance) (protocol II). The protein homogeneity (a single electrophoretic band) of the monomeric protease was confirmed by both methods after precipitation with 80% saturated ammonium sulphate. Moreover, the fractional precipitation technique with this salt (40 and 80%) was useless in the experimental conditions employed and an important loss of activity was observed (28.53%) with a 3-fold purification. In another part of the study, without ammonium sulphate precipitation, the gel filtration enabled the elimination of almost 97% of the inactive proteins and improved the activity performance by 55.13%, while multiplying the specific activity of the coagulant by a factor of 20.88 against a 6.75-fold purification with ionexchange and the appearance of a more or less 20 kDa peptide after electrophoresis. The proteolytic activity of the purified extracts had a similar appearance to a more pronounced kinetic when compared with the reference rennet. The purification protocols did not seem to have an impact on the isolated protease activity
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    Extracellular protease from mucor pusillus : purfication and characterization
    (2009) Nouani, A.; Belhamiche, N.; Slimani, R.; Fazouane, F.; Belbraouet, S.; Bellal, M.
    Extracellular protease from Mucor pusillus was purified 18-fold with 7.56% recovery by ion-exchange chromatography and gel filtration. The enzyme was found to be monomeric in nature, having a molecular mass of 49 kDa. The enzyme acted optimally at 50°C and was stable in the temperature range 30–50°C. It was completely inactivated by heating for 30 min at 65°C. The optimum of activity for the purified extract was observed at milk CaCl2 concentration of 0.02 m and at milk pH of 5. These properties, except for temperature, were similar to those of rennet