Purification and Characterization of Bioactive Metabolite from Streptomyces monomycini RVE129 Derived from the Rift Valley Soil of Hawassa, Ethiopia.

Streptomyces species have produced a variety of bioactive secondary metabolites with intriguing antimicrobial and anticancer properties. In this study, the bioactive compound obtained from the potent strain RVE129 was purified and characterized. Its bioactivity against various pathogens and its cytotoxicity toward the human cervical cancer (HeLa) cell were also examined. The strain was previously isolated from unexplored areas of the rift valley soil of Hawassa (Ethiopia) and identified by phenotypic characteristics and complete sequencing of the 16S rRNA gene and found to be closely related to Streptomyces monomycini strain NRRL B-24309 (99.65%); accession no. (ON786620). The active fraction undergoes bioassay-guided purification using the TLC method after being extracted by ethyl acetate. Then, it was subjected to physicochemical and structural characteristics using UV-Vis, FTIR, and NMR spectroscopic methods. A minimum inhibitory concentration of the purified antibiotic was achieved by the broth microdilution method. The cytotoxicity of HeLa cells was determined using the 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The acquired data from spectroscopic studies was compared with that of the reported natural compounds in data bases and found to be the known antibiotic, setamycin. The antibiotic (RVE-02) showed a broad spectrum of bioactivity against both Gram-positive and Gram-negative bacteria, with MIC values that ranged from 1.97 to 125 µg/ml. The bioactivity results also demonstrated antiproliferation and morphological change in HeLa cells with an IC50 value of 24.30µg/ml of antibiotic. The antibiotic, obtained from S. monomycini RVE129, could be a potential candidate to combat pathogens including drug-resistant S. aureus. Further, the effect on HeLa cells suggests that it could be a prominent cancer chemotherapeutic agent.

Antimicrobial Potential of Streptomyces spp. Isolated from the Rift Valley Regions of Ethiopia.

The study was undertaken to isolate, screen, and identify actinomycetes with antimicrobial metabolites. Twenty-one composite soil samples were randomly collected from various unique agroecological niches in the Rift Valley of Ethiopia. The soil samples were serially diluted and spread on starch casein agar medium supplemented with 50 µg/ml cycloheximide and 25 µg/ml nalidixic acid. Two hundred and forty-nine (249) actinomycetes cultures were isolated and screened by cross streaking against various human pathogens. Twenty-four isolates with pronounced antimicrobial activity were selected for identification and further screening. Among the isolates, 172 (69.1%) showed antimicrobial activities against tested pathogens. The inhibition zone of the isolates ranged from 5 ± 0.31 to >40 mm during primary screening. The antimicrobial activity of the crude extracts of promising isolates showed a statistically significant difference (P < 0.05) between them and the control. The isolates RVE129 and RVE217 showed the maximum zone of inhibition at 27 ± 0.6 mm and 26 ± 0.6 mm, respectively, against S. aureus, and the results were higher than the standard drug streptomycin (25 ± 0.58 mm). The inhibition zone of crude extracts from RVE129 was at the maximum of 22 ± 0.0 mm against P. aeruginosa, almost comparable to the standard drug streptomycin (24 ± 0.58 mm). Crude extract from the isolates RVE129 and RVE187 showed higher inhibition zones of 22 ± 0.6 mm and 16 ± 0.33 mm against A. niger ATCC10535, which, however, were smaller than those obtained with the standard drug amphotericin B (29 ± 0.6 mm). Twenty-four actinomycete strains with remarkable bioactivity were characterized using various cultural, morphological, physiological, and biochemical characteristics and assigned under the genus Streptomycetes. The finding of the current study indicates that Streptomyces sp. isolated from the Rift Valley of Ethiopia was found to possess a broad spectrum of bioactivity against a range of human pathogens.

Characterization of biosorption potential of Brevibacillus biomass isolated from contaminated water resources for removal of Pb (II) ions.

Various activities of different industries are found to be the main reason for water pollution with heavy metals. Use of microorganisms that are tolerant even of a high concentration of metal ions could be a valuable tool for remediation of contaminated water resources. In the present study, microorganisms that showed high resistance to lead ions were isolated and evaluated for biosorption efficiency for removal of lead ions from waste water. Biochemical identification and 16S rRNA gene sequence analysis indicated that the isolated strain was Brevibacillus. The conditions of pH, biomass concentration, temperature, time, agitation and Initial concentration of metal for biosorption of Pb (II) were optimized. Based on induction coupled plasma optical emission spectroscopy (ICP-OES) analysis, the biosorption efficiency of Brevibacillus at optimized conditions of initial metal concentration of 150 µg/mL, 1 g/L of biomass dose, pH 6.0, 40 °C, for 12 h at 80 rpm was 78.58% and the biosorption capacity (qe) is 128.58 mg/g of the biosorbent. Of the three isotherm models investigated, the Freundlich isotherm model was identified as a good fit with high correlation coefficient, while kinetic data followed the pseudo first order model as best fit. Surface characterization by scanning electron microscopy (SEM) analysis revealed morphological changes with a bulged rod-shape cell having metal depositions and rough texture. The presence of lead within the cell was detected by transmission emission microscopy (TEM). The key functional groups that participate in biosorption were analyzed by Fourier transform infrared (FTIR) spectroscopy and were found to be carboxyl, hydroxyl, amino and phosphate groups. From the real-time study, it proves that the biomass of Brevibacillus can be used as a promising biosorbent for removal of metals including lead from waste water.

Comparative Analysis of Structural Variations Due to Genome Shuffling of Bacillus Subtilis VS15 for Improved Cellulase Production.

Cellulose is one of the most abundant and renewable biomass products used for the production of bioethanol. Cellulose can be efficiently hydrolyzed by Bacillus subtilis VS15, a strain isolate obtained from decomposing logs. A genome shuffling approach was implemented to improve the cellulase activity of Bacillus subtilis VS15. Mutant strains were created using ethyl methyl sulfonate (EMS), N-Methyl-N' nitro-N-nitrosoguanidine (NTG), and ultraviolet light (UV) followed by recursive protoplast fusion. After two rounds of shuffling, the mutants Gb2, Gc8, and Gd7 were produced that had an increase in cellulase activity of 128%, 148%, and 167%, respectively, in comparison to the wild type VS15. The genetic diversity of the shuffled strain Gd7 and wild type VS15 was compared at whole genome level. Genomic-level comparisons identified a set of eight genes, consisting of cellulase and regulatory genes, of interest for further analyses. Various genes were identified with insertions and deletions that may be involved in improved celluase production in Gd7.. Strain Gd7 maintained the capability of hydrolyzing wheatbran to glucose and converting glucose to ethanol by fermentation with Saccharomyces cerevisiae of the wild type VS17. This ability was further confirmed by the acidified potassium dichromate (K2Cr2O7) method.

Structural Changes of Bacillus subtilis Biomass on Biosorption of Iron (II) from Aqueous Solutions: Isotherm and Kinetic Studies.

Various microbial biomasses have been employed as biosorbents. Bacterial biomass has added advantages because of easy in production at a low cost. The study investigated the biosorption of iron from aqueous solutions by Bacillus subtilis. An optimum biosorption capacity of 7.25 mg of the metal per gram of the biosorbent was obtained by the Inductive Coupled Plasma Optical Emission Spectroscopy (ICP-OES) under the experimental conditions of initial metal concentration of 100 mg/l, pH 4.5, and biomass dose of 1 g/l at 30°C for 24 hrs. The data showed the best fit with the Freundlich isotherm model while following pseudo-first-order kinetics. Scanning Electron Microscope (SEM) and Energy Dispersive X-ray (EDX) analysis confirmed iron biosorption as precipitates on the bacterial surface, and as a peak in the EDX spectrum. The functional hydroxyl, carboxyl, and amino groups that are involved in biosorption were revealed by the Fourier Transform Infrared spectroscopy (FTIR). The amorphous nature of the biosorbent for biosorption was indicated by the X-ray Diffraction (XRD) analysis. The biomass of B. subtilis exhibited a point zero charge (pHpzc) at 2.0.Various microbial biomasses have been employed as biosorbents. Bacterial biomass has added advantages because of easy in production at a low cost. The study investigated the biosorption of iron from aqueous solutions by Bacillus subtilis. An optimum biosorption capacity of 7.25 mg of the metal per gram of the biosorbent was obtained by the Inductive Coupled Plasma Optical Emission Spectroscopy (ICP-OES) under the experimental conditions of initial metal concentration of 100 mg/l, pH 4.5, and biomass dose of 1 g/l at 30°C for 24 hrs. The data showed the best fit with the Freundlich isotherm model while following pseudo-first-order kinetics. Scanning Electron Microscope (SEM) and Energy Dispersive X-ray (EDX) analysis confirmed iron biosorption as precipitates on the bacterial surface, and as a peak in the EDX spectrum. The functional hydroxyl, carboxyl, and amino groups that are involved in biosorption were revealed by the Fourier Transform Infrared spectroscopy (FTIR). The amorphous nature of the biosorbent for biosorption was indicated by the X-ray Diffraction (XRD) analysis. The biomass of B. subtilis exhibited a point zero charge (pHpzc) at 2.0.

Characterization of Exopolysaccharide Produced by Streptococcus thermophilus CC30.

An exopolysaccharide (EPS) producing strain CC30 was isolated from raw milk and identified as Streptococcus thermophilus with morphological and 16S sequencing analysis. The strain was shown to produce 1.95 g/L of EPS when grown in skim milk lactose medium at 30°C by increasing the viscosity of the medium. The EPS was isolated and purified, and it was shown to consist of glucose and galactose in 1 : 1 ratio, with molecular weights ranging from 58 to 180 kDa. FTIR spectroscopy indicated the EPS to have amide, hydroxyl, and carboxyl groups. Under Atomic Force Microscopy, EPS showed spike-like lumps of EPS. Scanning Electron Microscopy (SEM) studies showed that it had irregular lumps with a coarse surface. The EPS displayed pseudoplastic nature. Thermogravimetric analysis (TGA) reported a degradation temperature of 110.84°C. The purified EPS exhibited reducing activity, hydrogen peroxide radical scavenging activity, and emulsification activity. The results of the present study indicated that EPS producing Streptococcus thermophilus could serve as a promising candidate for further exploitation in food industry.