Optimization of glycerol-based medium composition for antifungal metabolites production by Bacillus subtilis

Abstract Bacillus species are promising producers of various compounds that have pronounced antimicrobial, antiviral and antitumor activities. Due to its GRAS status, Bacillus subtilis represents an excellent candidate for the usage in plant pathogens biocontrol. In this research, evaluation of antifungal metabolites biosynthesis by Bacillus subtilis ATCC 6633 and optimization of glycerol-based medium composition, using response surface methodology, for the production of compounds effective against Neurospora crassa were investigated. The results of disc-diffusion method indicate that applied Bacillus strain produces compounds with antifungal activity against tested fungus. In order to find optimal cultivation medium composition, the experiments were carried out in accordance with Box-Behnken design, and optimization was performed using the concept of desirability function combined with previously defined mathematical equation, which describes examined bioprocess. The optimization model predicts that maximum inhibition zone diameter against Neurospora crassa of 32.24 mm is achieved when initial content of glycerol, NaNO2 and K2HPO4 were 49.68 g/L, 2.90 g/L and 6.49 g/L, respectively. Additionally, the second optimization set was made to minimize the consumption of medium components and costs of medium preparation. The obtained results are the basis for further research aimed to develop medium appropriate for economically justified production of bioactive compounds at industrial scale.

Antitumor compounds from Streptomyces sp. KML-2, isolated from Khewra salt mines, Pakistan

BACKGROUND: Actinomycetes are gram positive bacteria with high G + C content in their DNA and are capable of producing variety of secondary metabolites. Many of these metabolites possess different biological activities and have the potential to be developed as therapeutic agents. The aim of the present study was to screen actinomycetes inhabiting halophilic environment such as Khewra salt mines present in Pakistan for cytotoxic and antitumor compounds. RESULTS: An actiomycetes strain designated as Streptomyces sp. KML-2 was isolated from a saline soil of Khewra salt mines, Pakistan. The strain Streptomyces sp. KML-2 showed 84 % cytotoxic activity against larvae of Artemiasalina. In the screening phase, the strain exhibited significant antitumor activity with IC50 values of 12, 48 and 56 µg/ml against Hela, MDBK and Vero cell lines, respectively. After that extract from 20 l fermentation was used to purify secondary metabolites by several chromatographic techniques. Structure elucidation of isolated compounds revealed that it is highly stable producer of Chromomycin SA (1) and 1-(1H-indol-3-yl)-propane-1,2,3-triol (2). Both of the isolated compounds showed significant antitumor activity against Hela and MCF-7 cancer cell lines (IC50 values 8.9 and 7.8 µg/ml against Hela; 12.6 and 0.97 µg/ml against MCF-7, respectively). The 16S rRNA gene sequence (1437 bp) of the strain confirm its identity (99 %) with Streptomyces griseus. CONCLUSIONS: From this research work we were successful in isolating two potent antitumor compounds, Chromomycin SA and 1-(1H-indol-3-yl)-propane-1,2,3-triol from Streptomyces KML-2 strain, isolated from Khewra salt mine. As such this is the second report which confirms that S. griseus can produce Chromomycin SA without introducing any mutagenesis in its biosynthesizing gene cluster and isolated indole derivative is being reported first time from any member of actinomycetes group with having novel antitumor activity against Hela and MCF-7 cells Nucleotide sequences: Nucleotide sequence data reported are available in the GenBank database under the accession number: GenBank KJ009562.

influence of various silicones on the rheological parameters of AZG containing silicone-based gels

Aluminium zirconium tetrachlorohydrex glycine [AZG] is a popular antiperspirant/deodorant agent, formulated in various forms including the clear gels. Silicones are used for the preparation of these gels, giving them desirable characteristics. The aim of this study was to investigate the influence of various silicones, when used in combination, on the rheological properties of the resulting AZG gels prepared. Based on preliminary studies, various AZG containing silicone-based gel formulations were prepared. Silicones used [as ternary mixtures] included ABIL[R] EM 97, ABIL[R] 8839 and ABIL[R] 8852. Formulations prepared were then examined rheologically and their plastic viscosity and yield values determined. Results showed that the amount of ABIL[R] EM 97 [used as an emulsifier] present within the gel formulation is critical. An increase in the amount of this silicone, corresponding to a small decrease in the amount of the hydrophobic structure building [gelling agent] ABIL[R] B8839, increased the plastic viscosity and yield values of the gel. On the other hand, an excess amount of ABIL[R] B8852, as a hydrophilic co-surfactant, reduced the viscosity and yield values of the resulting gel. Eventually, among the formulations prepared, formulation F5 with suitable aesthetic and skin feel properties, spreadability and rheological behaviors, was selected for further studies. By constructing the up-curve and down-curve of this formulation, presence of a plastic thixotropic behavior was confirmed. Inclusion of various amounts of the hydrophobic silicone-based agent, dimethicone, within formulation F5 showed that by increasing the amount of dimethicone present, the plastic viscosity and yield values of the gel would be reduced. This reduction was significant at dimethicone concentrations above 0.5%. Furthermore, by increasing the amount of dimethicone present, the calculated "percentage of reduction in plastic viscosity" also increased. This means that the extent of thixotropicity of the gel formulation increases by the addition of dimethicone. This finding was also backed up by the resulting rheograms constructed. Overall, addition of 0.75% dimethicone produced the most acceptable product in terms of an appropriate viscosity, yield value and extent of thixotropicity. In conclusion, this study shows that in-depth rheological assessment of AZG gels prepared from silicones could be used as an important tool during their formulation and characterization in order to obtain an effective formulation with desirable properties