Halophilic microorganisms derived from diverse thalassohaline and athalassohaline environments including marine estuaries, saline and soda lakes, inland solar salterns and acidic habitats are categorized as slight-, moderate-and extreme halophiles according to their NaCl requirements. Taxonomic studies with culturable diversities of halophiles revealed that they belong to both Archaea and Bacteria representing the families Halobacteriaceae, Methanosarcinaceae and the class Gammaproteobacteria. As adaptive strategies against harsh salt stresses, majority of halophiles often synthesize and accumulate extracellular polysaccharides (EPS) which differ significantly in terms of their physical, chemical and material properties. So far the novelty in structure and functions of exopolysaccharides are concerned, producer strains belonging to the genera Halomonas and Haloferax have attracted the main attention. However, EPS producing strains belonging to the genera Idiomarina, Salipiger and Alteromonas are not uncommon. Through process optimization and metabolic regulation a number of potent halophilic strains have been found to produce copious amount of EPS indicating its commercial viability. Moreover, the significance of production, physico-chemical and biological properties along with the possible applications of halophilic EPS in industry and biotechnology have also been highlighted..
Objectives: Exploitation of bacterial endophytes for production of antimicrobial substances has led to the discovery of novel natural metabolites of diverse chemical nature. The present study focuses attention toward optimization of cultural conditions for production of antimicrobial compound(s) by an endophytic bacterium DL06 followed by its extraction and partial purification. Methods: The leaf endophytic bacterium Bacillus amyloliquefaciens DL06 (GenBank Accession no. MK696415, Microbial Culture Collection Accession no. 4186) isolated from carnivorous plant Drosera burmannii has been identified as a potent producer of antimicrobial metabolite following agar cup assay against several test bacterial and fungal strains. Cultural conditions for production of antimicrobials were optimized by “one variable at a time” method. The active fraction was isolated and purified partially using solvent extraction, thin-layer chromatography, and high performance liquid chromatography (HPLC) analysis. Results: B. amyloliquefaciens DL06 produced maximum antimicrobial compound in tryptic soy broth and Davis–Mingioli’s medium when grown under shake culture. Production of the antimicrobial metabolite has been optimized for the inoculum density, aeration, temperature, pH as well as carbon, and nitrogen sources. The antimicrobial metabolite was extracted from the cell-free culture filtrate in butanol and partially purified by silica gel column chromatography and HPLC. Conclusions: The antimicrobial metabolite, tentatively identified as quercetin showed broad spectrum bioactivity affecting several fungi and a number of Gram-positive and Gram-negative bacteria.
Abbreviations: P(3HB), poly (3-hydroxybutyrate); WRSM, weighted response surface methodology; PB, plackett-burman; CCD, central composite design; NMR, nuclear magnetic resonance; PHAs, polyhydroxyalkanoates; OVAT, one variable at a time; RSM, response surface methodology; DoE, design of experiment AbstractApplication of statistical models in developing strategies for process optimization and enhanced product yield is well established. The present study is focused to enhance poly (3-hydroxybutyrate) [P(3HB)] production by Bacillus cereus RCL 02, a leaf endophyte of oleaginous plant Ricinus communis L. using weighted response surface methodology (WRSM). The most influencing process variables for growth and bio-polyester accumulation were initially selected through Plackett-Burman (PB) designed experiments. Further, WRSM was applied to navigate the experimental data obtained in accordance with the central composite design (CCD). Interaction of three independent variables viz. carbon source (glucose), nitrogen source (yeast extract) and initial pH of the medium exerted most significant impact on biomass formation as well as P(3HB) production. A second order polynomial equation obtained from multiple regression analysis and the interaction studies from surface plots helped to determine the optimum concentrations of glucose (25g/L), yeast extract (4g/L) and initial pH (7.6). Validation of this statistical model was executed using point prediction tool of WRSM where-from the optimum values of all three significant variables were employed and experiments were conducted. Under such optimized conditions the endophytic isolate produced 8.07g/L of P(3HB), which was very close to the predicted value (7.80g/L) and thereby validated the model. Finally, the identity of the intracellularly accumulated bio-polyester of B. cereus RCL 02 was confirmed by proton nuclear magnetic resonance (1H NMR) spectroscopic analysis. Citation: Rituparna D, Arundhati P, Dutta G, et al. Application of weighted response surface methodology for enhanced poly (3-hydroxybutyrate) production by endophytic bacillus cereus RCL 02. Citation: Rituparna D, Arundhati P, Dutta G, et al. Application of weighted response surface methodology for enhanced poly (3-hydroxybutyrate) production by endophytic bacillus cereus RCL 02. Citation: Rituparna D, Arundhati P, Dutta G, et al. Application of weighted response surface methodology for enhanced poly (3-hydroxybutyrate) production by endophytic bacillus cereus RCL 02. Citation: Rituparna D, Arundhati P, Dutta G, et al. Application of weighted response surface methodology for enhanced poly (3-hydroxybutyrate) production by endophytic bacillus cereus RCL 02. Citation: Rituparna D, Arundhati P, Dutta G, et al. Application of weighted response surface methodology for enhanced poly (3-hydroxybutyrate) production by endophytic bacillus cereus RCL 02. Citation: Rituparna D, Arundhati P, Dutta G, et al. Application of weighted response surface methodology for enhanced poly (3-hydroxybutyrate) production by endophytic bacill...
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