Bolin Kumar Konwar

Microbial surfactant-enhanced mineral oil recovery under laboratory conditions

Microbial enhanced oil recovery (MEOR) is potentially useful to recover incremental oil from a reservoir being beyond primary and secondary recovery operations. Effort has been made to isolate and characterize natural biosurfactant produced by bacterial isolates collected from various oil fields of ONGC in Assam. Production of biosurfactant has been considered to be an effective major index for the purpose of enhanced oil recovery. On the basis of the index, four promising bacterial isolates: Pseudomonas aeruginosa (MTCC7815), P. aeruginosa (MTCC7814), P. aeruginosa (MTCC7812) and P. aeruginosa (MTCC8165) were selected for subsequent testing. Biosurfactant produced by the promising bacterial isolates have been found to be effective in the recovery of crude oil from saturated column under laboratory conditions. Two bacterial strains: P. aeruginosa (MTCC7815) and P. aeruginosa (MTCC7812) have been found to be the highest producer of biosurfactant. Tensiometer studies revealed that biosurfactants produced by these bacterial strains could reduce the surface tension (sigma) of the growth medium from 68 to 30 mN m(-1) after 96 h of growth. The bacterial biosurfactants were found to be functionally stable at varying pH (2.5-11) conditions and temperature of 100 degrees C. The treatment of biosurfactant containing, cell free culture broth in crude oil saturated sand pack column could release about 15% more crude oil at 90 degrees C than at room temperature and 10% more than at 70 degrees C under laboratory condition.

Bacterial biosurfactant in enhancing solubility and metabolism of petroleum hydrocarbons

Biosurfactant can make hydrocarbon complexes more mobile with the potential use in oil recovery, pumping of crude oil and in bioremediation of crude oil contaminant. In the investigation, bacterial isolates capable of utilizing poly-cyclic aromatic hydrocarbons like phenanthrene, pyrene and fluorene were used. A gradual decrease of the supplemented hydrocarbons in the culture medium was observed with corresponding increase in bacterial biomass and protein. The medium having the combined application of fluorine and phenanthrene caused better biosurfactant production (0.45 g l(-1)) and (0.38 g l(-1)) by Pseudomonas aeruginosa strains MTCC7815 and MTCC7814. The biosurfactant from MTCC7815 (41.0 microg ml(-1)) and MTCC7812 (26 microg ml(-1)) exhibited higher solubilization of pyrene; whereas, MTCC8165 caused higher solubilization of phenanthrene; and that of MTCC7812 (24.45 microg ml(-1)) and MTCC8163 (24.49 microg ml(-1)) caused more solubilzation of fluorene. Higher solubilization of pyrene and fluorene by the biosurfactant of MTCC7815 and MTCC7812, respectively enhanced their metabolism causing sustained growth. Biosurfactants were found to be lipopeptide and protein-starch-lipid complex in nature and they could reduce the surface tension of pure water (72 m Nm(-1)) to 35 m Nm(-1). The critical micelle concentration (CMC) was also lower than the chemical surfactant sodium dodecyl sulphate (SDS). They differed in quantity and structure. The predominant rhamnolipids present in biosurfactants were Rha-C(8)-C(10) and Rha-C(10)-C(8).

Nickel oxide nanoparticles: A novel antioxidant

We investigated a novel inorganic (nickel oxide) nanoparticles as a potential antioxidant in the biosystems. The particles were synthesized using self-propagating high-temperature synthesis (SHS) method at 650 degrees C. The antioxidant property of the nickel oxide particles was investigated in an in vitro system, using modified DPPH method for insoluble solid materials.

Biocompatible novel starch/polyaniline composites: Characterization, anti-cytotoxicity and antioxidant activity

Starch/polyaniline composites have been synthesized using oxidative polymerization of polyaniline in an aqueous dispersion of starch isolated from Colocasia esculenta corm. Scanning electron micrographs reveals the growth of polyaniline over the surface of the starch granules. DPPH scavenging and haemolysis prevention assay have been performed to estimate the antioxidant activity and cytotoxicity of the composites. Formation of new properties of the composites as compared to starch and poloyaniline was evident from the X-ray diffraction analysis (XRD). Characterization done using UV-Vis, FTIR and DSC analysis provide evidence of composite formation. Composite possesses antioxidant nature which increases with the concentration of polyaniline. The haemolysis prevention activity of these novel composite materials is found to increase as compared to the pure polyaniline with minor compromise in the antioxidant activity. The materials show tremendous potential for biomedical applications.

Biocompatible epoxy modified bio-based polyurethane nanocomposites: Mechanical property, cytotoxicity and biodegradation

Epoxy modified Mesua ferrea L. seed oil (MFLSO) based polyurethane nanocomposites with different weight % of clay loadings (1%, 2.5% and 5%) have been evaluated as biocompatible materials. The nanocomposites were prepared by ex situ solution technique under high mechanical shearing and ultrasonication at room temperature. The partially exfoliated nanocomposites were characterized by Fourier transform infra-red (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The mechanical properties such as tensile strength and scratch hardness were improved 2 and 5 times, respectively by nanocomposites formation. Even the impact resistance improved a little. The thermostability of the nanocomposites was enhanced by about 40 degrees C. Biodegradation study confirmed 5-10 fold increase in biodegradation rate for the nanocomposites compared to the pristine polymers. All the nanocomposites showed non-cytotoxicity as evident from RBC hemolysis inhibition observed in anti-hemolytic assay carried over the sterilized films. The study reveals that the epoxy modified MFLSO based polyurethane nanocomposites deserve the potential to be applicable as biomaterials.

Antioxidant activity and haemolysis prevention efficiency of polyaniline nanofibers.

Polyaniline (PAni) nanofibers have been synthesized by interfacial polymerization using hydrochloric acid (HCl) and camphor sulfonic acid (CSA) as dopants. The powder x-ray diffraction pattern of bulk polyaniline reveals ES I structure and has been indexed in a pseudo-orthorhombic lattice. The broadening of (110) reflection in the nanofiber samples has been analysed in terms of domain length and strain using a convolution method employing a Voigt function. The increase in d spacing for the (110) reflection in HCl-doped PAni nanofibers have been assigned to the change in structural conformation due to the increase in the tilt angle of the polymer chain, which is also evident from microRaman spectra. UV-vis spectra of the PAni nanofibers exhibit a remarkable blueshift in the absorption bands attributed to pi-pi* and pi-polaron band transitions indicating a reduction in particle size, which is also observed in TEM micrographs. The antioxidant activity of the polyaniline nanofiber samples has been investigated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging assay by employing UV-visible spectroscopy. It has also been observed that polyaniline nanofibers are able to protect the haemolysis of red blood cells (RBCs) from cytotoxic agents, namely H(2)O(2). The observed enhancement in the antioxidant and haemolysis prevention activity of the PAni nanofibers as compared to bulk has been attributed to the reduction in particle size and changes in structural conformation, as evident from TEM, XRD and microRaman spectroscopy.

Silver-embedded modified hyperbranched epoxy/clay nanocomposites as antibacterial materials.

Silver-embedded modified hyperbranched epoxy/clay nanocomposites were prepared at different wt.% of octadecyl amine-modified montmorillonite at a constant silver concentration (1 wt.%). UV-visible, XRD and TEM studies confirmed the formation of silver nanoparticles. Compared to the system without silver and clay, the gloss from 70° to 94°, scratch hardness from 4 to 5.8 kg, impact strength from 60 to 90 cm, tensile strength from 8.5 to 15.5 MPa, adhesive strength from 5 to 7.1 × 10(9)N/m, flexibility from >6 to <4mm, and thermostability from 230 to 260 °C increased for the modified system. Resistance to aqueous 10% HCl, 0.5% NaOH, 10% NaCl also increased. The nanocomposites showed antibacterial activity in well diffusion assays against Staphylococcus aureus (ATCC11632), Bacillus subtilis (ATCC11774), Escherichia coli (MTCC40), Pseudomonas aeruginosa (MTCC7814) and Klebsiella pneumoniae (ATCC10031). The results showed that these nanocomposites have potential to be used as antimicrobial materials.

‘Poly(ethylene glycol)-magnetic nanoparticles-curcumin’ trio: Directed morphogenesis and synergistic free-radical scavenging

Research on curcumin (polyphenol derived from the rhizome of herb Curcuma longa) has occupied a unique niche owing to its distinctive properties, unique molecular architecture and multi-potent efficacies, particularly in the bio-medical domain with recent interest in material science. In the present study, conjugation of curcumin onto biocompatible poly(ethylene glycol)--templated magnetic iron oxide nanoparticles (MNP) (2-5 nm), prepared through a simple wet chemical route is reported along with modulation of the activity of the partners. Statistical optimization, using response surface methodology, of sonication parameters (8 min, 0.4 cycle and 60% amplitude) for maximal curcumin loading (86%), has shown major morphology directing effect generating triads, tetrads, amongst others and chain-like arrangement (TEM imaging) of the bio-conjugated nanoparticles (80-90 nm). Intonation of the magnetometric parameters of the PEG assisted MNPs on bioconjugation was also evident. The synergistic potency of the partners, the polymer templated iron oxide nanoparticles and curcumin, was unmasked during scavenging of diphenyl picryl hydrazyl (DPPH). The system represents an architecturally appealing, magnetically responsive bio-conjugated system possessing synergistic participation of the partners, with prospective applications in medical domain.

Assessment of five soil DNA extraction methods and a rapid laboratory-developed method for quality soil DNA extraction for 16S rDNA-based amplification and library construction

Extraction of DNA from soil samples using standard methods often results in low yield and poor quality making them unsuitable for community analysis through polymerase chain reaction (PCR) due to the formation of chimeric products with smaller template DNAs and the presence of humic substances. The present study focused on the assessment of five different methods for metagenomic DNA isolation from soil samples on the basis of processing time, purity, DNA yield, suitability for PCR, restriction digestion and mDNA library construction. A simple and rapid alkali lysis based on indirect DNA extraction from soil was developed which could remove 90% of humic substances without shearing the DNA and permits the rapid and efficient isolation of high quality DNA without the requirement of hexadecyltrimethylammonium bromide and phenol cleanup. The size of DNA fragment in the crude extracts was >23 kb and yield 0.5-5 μg/g of soil. mDNA purification using Sephadex G-50 resin yielded high concentration of DNA from soil samples, which has been successfully used for 16S rDNA based amplification of a 1500 bp DNA fragment with 27F and 1492R universal primers followed by restriction digestion and mDNA library construction.

Optimization of Nutrient Requirements and Culture Conditions for the Production of Rhamnolipid from Pseudomonas aeruginosa (MTCC 7815) using Mesua ferrea Seed Oil

Environmental awareness has led to a serious consideration for biological surfactants and hence non-edible vegetable oils may serve as a substitute carbon source for bio-surfactant production (rhamnolipid) which might be an alternative to complex synthetic surfactants. There are reports of rhamnolipid production from plant based oil giving higher production than that of glucose because of their hydrophobicity and high carbon content. Therefore the contribution of non-edible oil such as Mesua ferrea seed oil could serve as a good carbon source for rhamnolipid production. Moreover the use of rhamnolipid production from non-edible plant based seed oil has not been reported elsewhere. The present work focus on the optimal production of rhamnolipid by considering both micro and macro nutrients and culture conditions using response surface methodology. The study observes that micronutrients play a significant role in rhamnolipid production from Pseudomonas aeruginosa (MTCC 7815). The investigation results with the statistically optimize parameters able to produce a higher rhamnolipid production and this methodology could be used to optimize the nutrients requirements and culture conditions. The present findings would assist in bioremediation of crude oil contaminated ecosystems.