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Currently, the chemically synthesized carotenoid pigments, fulfill the needs of the consumers and industries. However, owing to their toxic effects, the use of such chemical oriented pigment products have limitations by restrictions of usage; and such restrictions have necessitated finding ecofriendly alternative pigments. By the way, bacteria, fungi and plants are the prospective alternative natural resources for the production of pigments, similar to carotenoids. Carotenoids are natural pigments that are used widely in nutraceutical, food and pharma industries. Lately, the biological production of carotenoids from microbes has been receiving greater attention and in this aspect, the studies on bacterial sources are emerging proportionally. During a screening process of pigmented strains, the bacterial strain, Dietzia maris AURCCBT01 was isolated and on further study found it to be a producer of canthaxanthin. The process parameters for biomass and canthaxanthin production were statistically optimized using response surface methodology. The effect of process parameters, namely glucose (5–20 g/L), NaCl (0.2 – 1.0 g/L) and pH (5 – 7) on the biomass and canthaxanthin production were studied. The optimal conditions for biomass and canthaxanthin production were glucose, 12.5 g/L; NaCl, 0.6 g/L and pH, 7 resulting in the highest canthaxanthin yield of 2997 µg/L and biomass of 3.03 g/L. The results exposed that these three process variables had greater influence on the production of canthaxanthin by the strain Dietzia maris AURCCBT01. The scale-up study was carried out in a jar fermenter under the optimized conditions. The maximum production for canthaxanthin and biomass was 3103 µg/L, 3.2 g/L was achieved respectively, and the results are encouraging for optimization under industrial conditions.

As an investigative study, the potent bacterium Serratia marcescens SB08 was screened from the enteric gut of sulfur butterfly (Kricogonia lyside). Its pigment potential was tested, and the pigment was identified as prodigiosin by structural studies using High Performance Liquid Chromatography (HPLC), Gas Chromatography–Mass Spectroscopy (GC–MS), Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR). Various conditions, including pH, reaction time, temperature, color intensity, and fastness properties, were studied for pure silk, China silk, and cotton yarns, and the conditions for effective dyeing were optimized. Further, the pigment’s antimicrobial pursuit was tested to counter the common pathogens Bacillus subtilis MTCC2388, Escherichia coli MTCC443, Klebsiella pneumonia MTCC109, Proteus vulgaris MTCC1771, and Pseudomonas aeruginosa MTCC1688. The pigment was largely effectual and exhibited utmost zones of inhibition, thus demonstrating the finest antimicrobial effect against the microbes tested. The textile yarn materials soaked with this intrinsic dye pigment also exhibited antimicrobial action.

Novel benzimidazoquinoline derivative (AVT) was synthesized through a substitution reaction and characterized by various spectral techniques. Analyzing the optical properties of AVT under absorption and emission spectral studies in different environments exclusively with respect to solvents and pH, intriguing characteristics viz. aggregation induced emission enhancement (AIEE) in the THF solvent and ‘On-Off’ pH sensing were found at neutral pH. Sensing nature of AVT with diverse metal ions and bovine serum albumin (BSA) was also studied. Among the metal ions, Fe 3 + ion alone tunes the fluorescence intensity of AVT probe in aqueous medium from “turn-on” to “turn-off” through ligand (probe) to metal charge transfer (LMCT) mechanism. The probe AVT in aqueous medium interacts strongly with BSA due to Fluorescence Resonance Energy Transfer (FRET) and the conformational change in BSA was further analyzed using synchronous fluorescence techniques. Docking study of AVT with BSA reveals that the active site of binding is tryptophan residue which is also supported by the experimental results. Interestingly, fluorescent AVT probe in cells was examined through cellular imaging studies using BT-549 and MDA-MB-231 cells. Thus, the single molecule probe based detection of multiple species and stimuli were described.

In this work, the synthesis of silver nanoparticles from a pigment produced by a recently-discovered bacterium, Chryseobacterium artocarpi CECT 8497, was achieved, followed by an investigation of its anticancer properties. The bacterial pigment was identified as flexirubin following NMR ((1)H NMR and (13)C NMR), UV-Vis, and LC-MS analysis. An aqueous silver nitrate solution was treated with isolated flexirubin to produce silver nanoparticles. The synthesised silver nanoparticles were subsequently characterised by UV-Vis spectroscopy, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), X-Ray Diffraction (XRD), and Fourier Transform Infrared (FTIR) Spectroscopy methodologies. Furthermore, the anticancer effects of synthesised silver nanoparticles in a human breast cancer cell line (MCF-7) were evaluated. The tests showed significant cytotoxicity activity of the silver nanoparticles in the cultured cells, with an IC50 value of 36μgmL(-1). This study demonstrates that silver nanoparticles, synthesised from flexirubin from C. artocarpi CECT 8497, may have potential as a novel chemotherapeutic agent.