Chandrakant P. Narkhede

Towards an understanding of bacterial metabolites prodigiosin and violacein and their potential for use in commercial sunscreens

To exploit the microbial ecology of bacterial metabolite production and, specifically, to: (i) evaluate the potential use of the pigments prodigiosin and violacein as additives to commercial sunscreens for protection of human skin, and (ii) determine antioxidant and antimicrobial activities (against pathogenic bacteria) for these two pigments.

Screening of Rubiaceae and Apocynaceae extracts for mosquito larvicidal potential

Rubiaceae and Apocynaceae families are well known for the expression of cyclotides having insecticidal properties. Leaves and flowers extracts of plants from the families Rubiaceae (Ixora coccinea) and Apocynaceae (Allamanda violacea) were evaluated for mosquito larvicidal effect against early IVth instars of Aedes aegypti and Anopheles stephensi. Two forms of plant extracts, one untreated and the other treated with heat and proteolytic enzyme were used for assay. After primary assay, the extract showing more than 50% inhibition was further used for quantification purpose. LC50 and LC90 values of all the extracts were found to be reduced with the treated form. Phytochemical analysis of plant extracts was performed. Primary confirmation for the presence of cyclotides was done by Lowry test, thin layer chromatography and haemolytic assay. This novel approach merits use of plant extracts in mosquito control programmes.

Prospective of Microbial Exopolysaccharide for Heavy Metal Exclusion

Metals as a resource are depleting, and on another side, it fetches serious environmental pollution causing a threat to human health and ecosystem. The heavy metal accumulation due to anthropogenic activities results in toxicological manifestation. The traditional methods of remediation are not cost effective, efficient, and ecofriendly which necessitate and motivate towards the safe, effective, and ecofriendly biological methods. The increasing presence of heavy metals in the microbial habitat compels the microbes to develop the ability to tolerate or resist the presence of heavy metals. Exopolysaccharide (EPS) production is one of the strategies of microbes to fight against metal stress. EPS is a microbial biopolymer which is generally produced under stress from harsh environment and nutrition conditions. EPSs are cell-associated or secreted outside the cell and comprised organic macromolecules such as polysaccharides, proteins, and phospholipids in addition to some non-polymeric molecules. EPSs work as competent biosorbents with an anionic reactant group that effectively sequesters cationic heavy metals by electrostatic interactions. The present paper summarizes the EPSs with its types, role, and biosynthesis and an endeavor to elucidate the interaction mechanism of EPSs with heavy metal with supportive and distinctive applications for heavy metal exclusion. The review concluded with the current challenges and future prospects to make the EPS an efficient biosorbent.

Phytosynthesized Gold Nanoparticles-Bacillus thuringiensis (Bt–GNP) Formulation: A Novel Photo Stable Preparation Against Mosquito Larvae

It is well-known that the sunlight irradiation damages the spores and toxin produced by Bacillus thuringiensis (Bt), which leads to loss of their insecticidal activity. This photodegradation problem is addressed in the present investigation by use of green phytosynthesized gold nanoparticles (GNP) as a photoprotectant. The efficiency of Bt with GNP before and after exposing to sunlight was evaluated against the larvae of Aedes aegypti and Anopheles subpictus. The bioassay results focused that after sunlight irradiation the Bt significantly lose their activity for Ae. aegypti (23.13%) and An. subpictus (27.08%). Although the individual GNP showed very less activity against tested larvae, it was observed that in combination with Bt it significantly enhances activity and consequently reduced the LC50 of Bt–GNP. Similarly, even after irradiation of Bt–GNP formulation, the enhanced activity was found against Ae. aegypti (23.10%) and An. subpictus (27.24%). Henceforth in the case of Bt–GNP formulation, the GNP it was not only protecting the Bt from sunlight but enhances its larvicidal potential. The interactions between the GNP and Bt toxin which might be the main reason to protect the Bt from sunlight and can help to locate the Bt toxin at the target site.