Production optimization, characterization, and covalent immobilization of a thermophilic Serratia rubidaea lipase isolated from an Algerian oil waste.

A new thermophilic non-induced lipase producer named Serratia rubidaea strain Nehal-mou was isolated from oil waste in Tissemsilat, Algeria. The most influential lipase production parameters were screened by the Plackett-Burman design for enhancing enzyme yield. An optimum condition of a 1.5% of glucose, a 0.01% of potassium, and a 0.025% of manganese contents resulted in a 41.13 U/mL. This yield was 6.29 times higher than the one achieved before the application of the Box-Behnken Design. Lipase activity showed a high organic solvent tolerance following its exposure to hexane, ethanol, methanol, and acetone. Lipase was also perfectly stable in the presence of 10 mM Fe2+, K+, and Na+ ions with more than 75% of the retaining activity. The enzyme half-life times were 22 h, 90 min, and 25 min at 50, 60, and 70 °C respectively. Polyvinyl alcohol (PVA)/boric acid/Starch/CaCO3 were utilized as a carrier for lipase covalent immobilization in order to be used efficiently. The Scanning Electron Microscopy (SEM) Technique and the Fourier Transform Infrared Spectroscopy (FTIR) Method confirmed the covalent bonding success and the excellent carrier characteristics. Thus, the immobilization yield reached 73.5% and the optimum temperature was shifted from 40 to 65 °C. The immobilized lipase kept 80% of its total activity after 10 cycles and had 3 and 3.2-fold half-lives at 70, and 80 °C respectively compared to the free enzyme.

Characterization, high production and antimicrobial activity of exopolysaccharides from Lactococcus lactis F-mou.

A new exopolysaccharide (EPS) was produced by the Lactococcus lactis F-mou strain (LT898177.1) isolated from the Sahrawi camel milk in the Bir-Naam region, Algeria. The most influential production parameters were screened by the Plackett-Burman design for enhancing EPS yield utilizing the Mech-Degla juice as a low-cost raw material. An optimum condition of a 0.49 of inoculum size, a 100 rpm of agitation rate, and a 12 h of incubation period resulted in a 301 g/L. This yield was 47 times higher than the one attained before the application of the Box-Behnken Design. Additionally, the FTIR analysis of the EPS confirmed the presence of hydroxyl, carboxyl, amide and sulphate groups. Furthermore, the SEM image showed a porous structure characterized by a flake-like basic configuration with an extremely dense assembly. The NMR studies indicated that EPS contained a backbone of→4-α-D-galactopyranose-(1→, →4, 6-α-D-glucopyranose-(1→, →6- α -D- galactopyranose -(1→ linkages plus a levan part. The EPS exhibited good water and oil holding capacities, a high antioxidant efficiency, and an excellent anti-clotting activity. EPS also showed a strong inhibitory activity against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Listeria monocytogenes, Bacillus cereus, Proteus mirabilis, Acinetobacter baumannii, Enterobacter cloacae, and Candida albicans. Overall, the mentioned findings indicated that EPS could be utilized as a natural additive in pharmaceutical, food, and cosmetic industries.

Biochemical and molecular characterization of a lipase from an Algerian isolated Staphylococcus aureus strain.

A Staphylococcus aureus strain, isolated from an Algerian biotope, secretes a non-induced lipase in the culture medium. The S. aureus lipase (SAL) was purified to homogeneity. Pure SAL is a monomeric protein (43 kDa). The 20 N-terminal amino acid residues showed a high degree of homology with other staphylococcal lipase sequences. SAL presents specific activities of about 1600 and 555 U mg-1 using tributyrin and olive oil emulsion as substrates, respectively. In contrast to other staphylococcal lipases previously characterized, SAL was stable at a pH range from 6 to 9 after 1 h incubation, and retained 50% of its activity after 10 min incubation at 50 °C. The purified enzyme was also characterized using monolayer technique. Lipase activity can be measured only when the surface pressure exceeds 15 mN m-1 . The critical surface pressure (πc ) measured with egg-PC films was estimated at 33 mN m-1 . SAL showed a preference for the distal ester groups of the diglyceride isomers at low surface pressure, for the adjacent ester groups at high surface pressure and a preference for the sn-3 position of the 2,3-sn-enantiomer of dicaprin. Cloned and sequenced gene part, encoding the mature lipase shows, in comparison with S. aureus lipase 3 (SAL3), a deletion of three residues (LKA) at the N-terminal extremity and a substitution of glycine 208 and isoleucine 226 with an arginine and leucine, respectively.