Browsing by Author "Ankit K. Singh"

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Bioaccumulation of selenium in halotolerant microalga Dunaliella salina and its impact on photosynthesis, reactive oxygen species, antioxidative enzymes, and neutral lipids
(Elsevier Ltd, 2023) Prabhakar Singh; Sakshi Singh; Priyanka Maurya; Abhishek Mohanta; Hardik Dubey; Sk. Riyazat Khadim; Ankit K. Singh; Adarsh K. Pandey; Arvind K. Singh; Ravi K. Asthana
Selenium (Se) is an essential element for living systems, however, toxic at higher levels. In the present study, Dunaliella salina cells were exposed to different Se concentrations for their growth (EC50 195 mg L−1) as well as Se accumulation. The cells exposed to 50 mg L−1 Se showed photoautotrophic growth parallel to control and accumulated 65 μg Se g−1 DW. A decrease in photosynthetic quantum yield, chlorophyll content, and the increase in intracellular reactive oxygen species, proline content, and lipid peroxidation accompanied by higher neutral lipid accumulation, were recorded at higher Se level. The enzymes superoxide dismutase and catalase played a pivotal role in antioxidative defense. Heterogeneity in accumulated carotenoids at varying concentrations of selenium was prevalent. The cells exposed to 200 mg L−1 Se resulted in the disorganization of organelles. Thus, the Se enriched biomass obtained at 50 mg L−1 may be explored for bio-fortification of food and feed. © 2023 Elsevier Ltd
Bioactive molecules from microalgae and constraints in commercialization
(Elsevier, 2020) Urmilesh Singh; Laxmi; Ankit K. Singh; Ravi K. Asthana
Increasing drug resistance in pathogenic microorganisms especially fungi and bacteria, menace caused by AIDS in modern society, spread of dreaded cancer disease worldwide, especially in third-world countries led the scientists to look at nature and little explored microalgae which seem to be a bioresource for biomolecules. Microalgae, in general, involve all microscopic algae including cyanobacteria which have originated on earth ~2.8 billion years ago. Modern knowledge of genomics, proteomics and understanding of the strategy of survival of such microalgal strains inhabiting various environments including extreme habitats must be endowed with specific metabolic pathways, producing specific biomolecules of synthetic biochemist’s interest. Bioassays of microalgal extracts clearly demonstrate their potential to kill fungi and bacteria and to inhibit growth of viral and cancer cells. The identification of target biomolecules is a difficult task. Modern instruments including chromatography and high-resolution mass spectrometry led to the isolation and identification of biomolecules. However, small quantities of biomolecules (µg/g dry weight) made it difficult to produce at large scale. This chapter reviews the state of the art in extraction, purification and extent of nanotechnology for its impact on microbial system as well as cancer cells. Constraints in commercialization of biomolecules and drug production and its overcoming strategies are also discussed. © 2021 Elsevier Inc.
Biochemical and physiological characterization of a halotolerant Dunaliella salina isolated from hypersaline Sambhar Lake, India
(Blackwell Publishing Inc., 2019) Prabhakar Singh; Riyazat Khadim; Ankit K. Singh; Urmilesh Singh; Priyanka Maurya; Anupam Tiwari; Ravi K. Asthana
The objective of the present study was to characterize intrinsic physiological and biochemical properties of the wall-less unicellular cholorophyte Dunaliella salina isolated from a hypersaline Sambhar Lake. The strain grew optimally at 0.5 M NaCl and 16:8 h L:D photoperiod along with maintaining low level of intracellular Na + even at higher salinity, emphasizing special features of its cell membranes. It was observed that the cells experienced stress beyond 2 M NaCl as evidenced by increased intracellular reactive oxygen species and antioxidative enzymes, nevertheless proline and malondialdehyde content declined sharply accompanied by higher neutral lipid accumulation. Salinity exceeding 2 M resulted decrease in photosynthetic quantum yield (Fv/Fm) and enhanced glycerol synthesis accompanied by leakage. Super oxide dismutase seemed to play a pivotal role in antioxidative defense as eight isoforms were expressed differentially while catalase and glutathione peroxidase showing no significant change in their expression at higher salinity. The ability of D. salina to grow in range of salinities by sustaining healthy photosynthetic apparatus along with accumulation of valuable products made this alga an ideal organism that can be exploited as resource for biofuel and commercial products. © 2018 Phycological Society of America
Identification of antifungal and antibacterial biomolecules from a cyanobacterium, Arthrospira platensis
(Elsevier B.V., 2021) Urmilesh Singh; Prabhakar Singh; Ankit K. Singh; Laxmi; Deepak Kumar; Ragini Tilak; Sushant K. Shrivastava; Ravi K. Asthana
Arachidonoyl dopamine and fluocinolone were identified as ‘active compounds’ from the methanolic extract of a species of cyanobacterium, Arthrospira platensis, isolated from a hypersaline lake in Rajasthan, India. In vitro testing of these compounds has shown potential antifungal activity as well as antibacterial activity against strains with multidrug resistance. A. platensis-derived methanolic crude extract and purified fractions were assayed against bacterial and fungal target pathogens prioritized by the World Health Organization (WHO). The active fractions were subjected to high-resolution liquid chromatography/mass spectrometry (HR-LC/MS). Molecular docking analysis of the screened compounds revealed that arachidonoyl dopamine showed a significant interaction with the enzyme sterol-14-alpha demethylase targeted by other antifungal drugs; likewise, fluocinolone interacted with the OMP-F porin protein present in the outer membranes of the bacteria. However, neither molecule has yet been reported from any cyanobacterial system until now. In vitro activity of both compounds clearly indicates their potential for the development and/or repurposing of antifungal and antibacterial drugs. © 2021 Elsevier B.V.