Conversion of Agroindustrial Wastes to Rhamnolipid by Enterobacter sp. UJS-RC and Its Role against Biofilm-Forming Foodborne Pathogens.

Rhamnolipid is the main group of biosurfactants predominantly produced by Pseudomonas aeruginosa, a ubiquitous and opportunistic pathogen, which limits its large-scale exploitation. Thus, cost-effective rhamnolipid production from a newly isolated nonpathogenic Enterobacter sp. UJS-RC was investigated. The highest rhamnolipid production (4.4 ± 0.2 g/L) was achieved in a medium constituting agroindustrial wastes (sugarcane molasses and corn steep liquor) as substrates. Rhamnolipid exhibited reduced surface tension to 72-28 mN/m with an emulsification index of 75%. The structural analyses demonstrated the presence of methoxyl, carboxyl, and hydroxyl groups in rhamnolipid. Mass spectra indicated eight rhamnolipid congeners, where dirhamnolipid (m/z 650.01) was the dominant congener. Rhamnolipid inhibited biofilm formation of Staphylococcus aureus in a dose-dependent manner, supported by scanning electron microscopy disclosing the disruption of the microcolony/exopolysaccharide matrix. Rhamnolipid's ability to generate reactive oxygen species has thrown light on the mechanism through which the killing of test bacteria may occur.

Pleiotropic Functions and Biological Potentials of Silver Nanoparticles Synthesized by an Endophytic Fungus.

In recent years, the biological synthesis of silver nanoparticles (AgNPs) from microorganisms has become an emerging trend for developing biocompatible nanomaterials that finds applications in nano and biomedical sectors. In the present study, we demonstrated a facile, green and eco-friendly method for AgNPs synthesis using the endophytic fungi (Colletotrichum incarnatum DM16.3) isolated from medicinal plant Datura metel and its in vitro antithrombin and cytotoxic activity. At first, biosynthesis of colloidal AgNPs was predicted by visual observation of color change and UV-visible spectra demonstrated specific surface plasmon resonance peak at 420 nm which confirmed the presence of nanoparticles. Microscopic analyses revealed the structure of highly aggregated, spherical and crystalline AgNPs in the diameter range of 5-25 nm. Transform infrared spectroscopy (FT-IR) spectral analysis confirmed the presence of probable biomolecules required for the reduction of silver ions. In vitro evaluation of thrombin activity demonstrates that AgNPs could exert strong inhibition against both thrombin activity (87%) and thrombin generation (84%), respectively. Further, in silico based mechanistic analysis yielded a better insight in understanding the probable amino acids responsible for AgNPs binding with thrombin protein. Similarly, in vitro cytotoxicity of synthesized AgNPs on human epithelial cells using MTT assay did not produce any substantial effects after 24 h exposure which indicates excellent biocompatibility nature, whereas notable toxicity was observed on human cancerous (HeLa) cells at 50 µg/mL (IC50 value). In addition, assessment of AgNPs at 10 µg/mL concentration via crystal violet method on biofilm forming Gram-positive (Vibrio cholerae) and Gram-negative bacteria (Bacillus cereus) revealed inhibition up to 85 and 46%, respectively. Overall, this study showed the possibility of microbially synthesized AgNPs as a potent inhibitor for managing acute thrombosis and highlighted their role for other biomedical applications.

A combined approach of physicochemical and biological methods for the characterization of petroleum hydrocarbon-contaminated soil.

Main physicochemical and microbiological parameters of collected petroleum-contaminated soils with different degrees of contamination from DaGang oil field (southeast of Tianjin, northeast China) were comparatively analyzed in order to assess the influence of petroleum contaminants on the physicochemical and microbiological properties of soil. An integration of microcalorimetric technique with urease enzyme analysis was used with the aim to assess a general status of soil metabolism and the potential availability of nitrogen nutrient in soils stressed by petroleum-derived contaminants. The total petroleum hydrocarbon (TPH) content of contaminated soils varied from 752.3 to 29,114 mg kg(−1). Although the studied physicochemical and biological parameters showed variations dependent on TPH content, the correlation matrix showed also highly significant correlation coefficients among parameters, suggesting their utility in describing a complex matrix such as soil even in the presence of a high level of contaminants. The microcalorimetric measures gave evidence of microbial adaptation under highest TPH concentration; this would help in assessing the potential of a polluted soil to promote self-degradation of oil-derived hydrocarbon under natural or assisted remediation. The results highlighted the importance of the application of combined approach in the study of those parameters driving the soil amelioration and bioremediation.

Isolation and characterization of a novel phenanthrene (PHE) degrading strain Psuedomonas sp. USTB-RU from petroleum contaminated soil.

The phenanthrene degrading novel bacterium strain USTB-RU was isolated from petroleum contaminated soil in Dagan oilfield, southeast of Tianjin, northeast China. The novel isolate was identified as Pseudomonas sp. USTB-RU on the basis of morphological, physicochemical characteristics and analysis of 16S rDNA gene sequence. The strain could degrade 86.65% of phenanthrene at an initial concentration of 100 mg L(-1) in 8 days and identified intermediate metabolite evident the biodegradation of phenanthrene through protocatechuate metabolic pathway. The strain showed the potential to produce surface-active compounds that may have caused for the resulted efficient biodegradation through enhancing the substrate bioavailability. The results highlighted that the adaptability of USTB-RU to grow in a range of temperature, pH and potential to utilize various commonly co-exist pollutants in contaminated site other than phenanthrene as sole carbon and energy source. Further, susceptibility of the strain for the tested antibiotics inferred the possibility to absence of risk of spreading drug resistant factor to other indigenous bacteria. Therefore, the isolated novel strain USTB-RU may have a high potential for application in in situ bioremediation of phenanthrene contaminated environment.

Effects of petroleum hydrocarbon contaminated soil on germination, metabolism and early growth of green gram, Vigna radiata L.

The objective of the present study was to evaluate effects of petroleum hydrocarbon contaminated soil on the leguminous plant, Vigna radiata L. Seed germination, metabolism and early growth performance of V. radiata L. were studied as parameters by applying a combined approach. The employed combined method which included microcalorimetry and analysis of the root cross section revealed dose dependent effects of petroleum hydrocarbon contaminated soil on V. radiata L. for most parameters. Although significant reductions in measured parameters were observed even at low total petroleum hydrocarbon (TPH) levels such as 1 % and 1.5 %, calculated inhibitions, IC50 values and metabolic heat emission-time curves inferred that substantial negative effects can be expected on V. radiata L. in soils with comparatively high contamination levels, such as 2.5 % TPH and higher.