Screening of different growth conditions of Bacillus subtilis isolated from membrane-less microbial fuel cell toward antimicrobial activity profiling.

Bacteriocins produced by Bacillus subtilis have gained recognition for their safe use in humans. In this study, we aimed to assess the inhibitory activity of an antimicrobial peptide synthesized by the wild-type strain of B. subtilis against the notorious pathogen Pseudomonas aeruginosa. Our investigation employed the broth microdilution method to evaluate the inhibitory potential of this peptide. Among the four different pathogen strains tested, P. aeruginosa exhibited the highest susceptibility, with an inhibition rate of 29.62%. In parallel, we explored the cultivation conditions of B. subtilis, recognizing the potential of this versatile bacterium for applications beyond antimicrobial production. The highest inhibitory activity was achieved at pH 8, with an inhibition rate of 20.18%, indicating the potential for optimizing pH conditions for enhanced antimicrobial peptide production. For the kinetics of peptide production, the study explored different incubation periods and agitation levels. Remarkably, the highest activity of B. subtilis was observed at 24 h of incubation, with an inhibition rate of 44.93%. Finally, the study focused on the isolation of the antimicrobial peptide from the cell-free supernatant of B. subtilis using ammonium sulfate precipitation at various concentrations. The highest recorded activity was an impressive 89.72% achieved at an 80% concentration.

Use of sodium alginate in the preparation of gelatin-based hard capsule shells and their evaluation in vitro.

Using only type B gelatin produces hard capsule shells which are too brittle. This study examines the blending of type B bovine gelatin with sodium alginate to produce hard capsule shells and through evaluation of their in vitro physicochemical properties provides a reflection on the role of gelatin and sodium alginate in the blend. The compositions and formulation of the capsule shells in this study comprised gelatin (10%, 20% and 30%), sodium alginate (1%, 2%, 3%, 4% and 5%), water, and opacifying agents (titanium dioxide; TiO2) and polyethylene glycol (PEG) whose concentrations were kept constant. From the 15 films prepared, five were found to form hard capsule shells. Increased concentrations of sodium alginate increased the viscosity of the blends accompanied by capsule thickening. There was a good molecular compatibility between gelatin and sodium alginate. Increased gelatin and sodium alginate concentrations increased the water-holding capacity of the film, which decreased the redness (a*), lightness (L*), blueness (b*), variation in the color parameters (ΔE*) and the whiteness index (WI). The weight of the capsule shells ranged between 0.080 g and 0.25 g and the moisture content was between 5% and 11%. Ash contents for all the formulations were below 5% and the sensitivity of capsules at pH 7 was higher than that at acidic pH. Highest rupture times were observed with simulated gastric fluid (SGF, pH 1) for all formulations. Increased gelatin concentration decreased the resistance of the capsule to force while increased sodium alginate concentration had no effect on resistance to force.