Varadharajan Kavitha

Microbial products (biosurfactant and extracellular chromate reductase) of marine microorganism are the potential agents reduce the oxidative stress induced by toxic heavy metals.

The present study demonstrates hexavalent chromium reduction and trivalent chromium tolerance behavior of marine Bacillus sp., MTCC 5514 through its extracellular enzyme reductase and biosurfactants production. The isolate reduces 10-2000 mg/L of hexavalent chromium to trivalent chromium with in 24-96 h respectively and the release of extracellular chromium reductase, found responsible for the reduction. Upon reduction, the concentration of trivalent chromium in the medium found comparatively less. Experimental results reveal, biosurfactants activity found responsible for the less concentration of Cr(III). Hypothetically, trivalent chromium upon formation get entrapped in the micelle of biosurfactants, prevents microbial cells from exposure towards trivalent chromium. Thus, the chosen isolate exhibit tolerance and growth with the increasing concentration of chromium.

Microbial surfactant mediated degradation of anthracene in aqueous phase by marine Bacillus licheniformis MTCC 5514

The present study emphasizes the biosurfactant mediated anthracene degradation by a marine alkaliphile Bacillus licheniformis (MTCC 5514). The isolate, MTCC 5514 degraded >95% of 300 ppm anthracene in an aqueous medium within 22 days and the degradation percentage reduced significantly when the concentration of anthracene increased to above 500 ppm. Naphthalene, naphthalene 2-methyl, phthalic acid and benzene acetic acid are the products of degradation identified based on thin layer chromatography, high performance liquid chromatography, gas chromatography and mass analyses. It has been observed that the degradation is initiated by the biosurfactant of the isolate for solubilization through micellation and then the alkali pH and intra/extra cellular degradative enzymes accomplish the degradation process. Encoding of genes responsible for biosurfactant production (licA3) as well as catabolic reactions (C23O) made with suitable primers designed. The study concludes in situ production of biosurfactant mediates the degradation of anthracene by B. licheniformis.

Bioremediation of Crude Oil Contamination Using Microbial Surface-Active Agents: Isolation, Production and Characterization

The present study highlights isolation, screening, production, characterization of marine microbial surface active agents followed by evaluating the ef fi cacy of said surface -active agents for bioremediation of crude oil contamination. Upon screening, six potential surface-active agents producing isolates of Bacillus genera with signi fi cant difference in their morphology were obtained from marine sediments of Tamil Nadu coastal area. Results from optimization studies revealed, sucrose and yeast extract were the suitable carbon and nitrogen sources for growth, pH of 7.2 ± 0.2, temperature of 37oC and agitation at 180-200 rpm were the other optimized variables for the maximum production of surface-active agents irrespective of the bacterial isolates. Extraction and characterization studies reveals, the product was polymeric in nature with the surface activity in the range of 28 ± 4 mN/m. Thermal stability was comparable with that of synthetic surfactants and exhibit appreciable emulsifying activity and emulsion stability (more than 90 days). Laboratory scale studies on removal of crude oil from aqueous phase demonstrate, >90% of crude oil was removed within 60-120 minutes of exposure to the partially puri fi ed surface-active agents. The percentage removal showed signi fi cant difference for the six different surface-active agents .

Phylogenetic Framework and Biosurfactant Gene Expression Analysis of Marine Bacillus spp. of Eastern Coastal Plain of Tamil Nadu

The present study emphasizes the diversity assessment of marine Bacillus species with special reference to biosurfactant production, respective gene expression, and discrimination among Bacillus licheniformis and Bacillus subtilis. Among the 200 individual species of eastern coastal plain of Tamil Nadu screened, five biosurfactant producing potential bacterial species with entirely different morphology were selected. Biochemical and 16S rRNA gene sequence analysis suggested that all the said five species belong to Bacillus genera but differ in species levels. Biosurfactant of all the five species fluctuates in greater levels with respect to activity as well as to constituents but showed partial similarity to the commercially available surfactin. The expression of srf gene was realized in all of the five species. However, the sfp gene expression was observed only in three species. In conclusion, both B. licheniformis and B. subtilis demonstrate srf gene; nevertheless, sfp gene was expressed only by Bacillus subtilis.

Biotransformation of soybean oil to a self-healing biopolymer

Abstract Soybean oil in the presence of mineral salts, peptone, carbohydrates, lipase, and lipopeptide transformed to a soft tissue-like material after 10-day incubation at 37°C with shaking at 200 rpm. When damaged, the resultant soft tissue self-healed in an aqueous medium. Analysis revealed that during the self-assembly process, components present in the aqueous medium were entangled in the soft tissue; upon damage, release of these components accelerated healing. Superficial damage resulted in smooth healing, whereas deep damage gave uneven healing similar to deep skin wounds.

Transformation of Soybean Oil to Various Self-Assembled Supramolecular Structures

Today’s research worlds try to bring everything in nanosize and the tremendous development on nanosize and technology introduced numbers of molecules with immense applications. Though nanostructures from numbers of metals and materials are being synthesized, supramolecular structures attracts the research group at increasing level, because of the interest and urge to know the origin of life. Hence, research groups at global level are making attempts on how the self-assembly and the supramolecular structures have been formed from the single and /or from the combination molecules. Thus the design and the construction of supramolecular assembly/structures are quite interesting and various hypothetical theories have been developed to substantiate the origin of life. Supramolecular structures are large molecules fashioned by binding of smaller molecules mutually and it often to develop molecules of preferred form including 2D triangles, squares, pentagons, hexagons and 3D octahedrons, cubes and some irregular shapes. Self-assembly is the most prevailing methodology in the design of large, distinct, ordered structures. The objects of supramolecular chemistry are defined on one hand by the nature of the molecular components and on the other by the type of interactions that hold them together. Three major steps are involved in supramolecular systems; (i) selective binding, (ii) growth of the components in the correct relative orientation and (iii) termination requiring a built in feature which signifies the end process. The chemistry of supramolecular structure is a constitutional dynamic chemistry due to the reversibility of the connecting events. The kinetic liability confers the self-assembling systems to undergo annealing and self-healing of defects and to manifest tunable degree of polymerization and cohesive properties. In contrast, covalent linked, nonlabile type cannot heal spontaneously and the defects are permanent (Lehn, 2005). According to Murakami, synthesis of supramolecular structure is based on the principle of molecular recognition and molecular self-assembly realized due to the formation of noncovalent interaction towards the cooperation of many weak bonds including electrostatic interaction, Van der Waals forces, dipole interaction, hydrogen bonding, hydrophobic interaction, and π–π interaction. Recently the interest was drawn to a new topological form of supramolecular structures by self-assembly and also by weak interactions.