Showing papers by "Ruma Pal published in 2020"

Investigation on the effects of nitrate and salinity stress on the antioxidant properties of green algae with special reference to the use of processed biomass as potent fish feed ingredient

Abstract: Antioxidant properties of four common green algal genera viz. Cladophora glomerata, Chaetomorpha aerea, Rhizoclonium crassipellitum, and Pithophora cleveana collected from Sunderban areas of Eastern India were tested in controlled and nutrient stress conditions. Experimental algae were exposed to growth media with variations in nitrate and NaCl salt concentrations from 0 to 1500 ppm level for a period of 21 days. A dose-dependent upregulation in total phenols, flavonoids, pigment, and antioxidant property in relation to % DPPH activity and % ferrous ion chelating activity was observed. Maximum phenol content was observed for algal biomass exposed to 1500 ppm nitrate stress conditions (52.55 ± 0.01 mg GAE/g DW-16.48 ± 0.041 mg GAE/g DW) with Rhizoclonium showing the maximum contents. In the case of total flavonoid content, maximum upregulation was noted in the hypersaline conditions and Pithophora showed the highest contents amongst all (71.8 ± 0.21 mg QE/g DW). The highest carotenoid contents were observed in 750 ppm stress condition. Optimally stressed algal biomass having maximum carotenoid levels and high antioxidant levels were selected as fish feed ingredients, based on dose- and time-dependent two-way Anova and Tukeys test (750 ppm nitrate, 7 days). The processed biomass was included as fish feed ingredient to study the nutritive effects on goldfish (Carassius auratus). Algal feed (AF) was prepared from algal biomass only, which was further mixed with the commercial feed (CF) in varying proportions to formulate three different types of value-added feed (VAF). The experimental feed (25% VAF, 50% VAF, 75%VAF and AF) were tested against commercial feed (control) for 30 days in artificially aerated static aquaria system. The feed type formulated as 50% VAF was found to be most effective in terms of skin pigmentation, growth, and antioxidant activities of experimental fishes showing almost (1.44–4-folds increase) compared to the control setup. Statistically significant results were obtained regarding nutritive properties of experimental feed and fishes using PCA and Tukeys test respectively. Body weight gain and specific growth rate also changed significantly in experimental fishes.

Utilization of nanoporous biosilica of diatoms as a potential source material for fabrication of nanoelectronic device and their characterization

Abstract: Biosilica obtained from frustules of diatoms have very delicate nanostructures similar to many micro- and nanofluidic devices. In the present investigation, a cheaper and ecofriendly metal-oxide-semiconductor (MOS) tool has been fabricated exploiting frustules of the diatom Halamphora subturgida. The structural, optical, and chemical characterizations of the cleaned frustules of cultured diatom were investigated through various techniques. Electron microscopic images revealed intricate morphology of the nanostructured silica with very minute pores making the frustules very hard but light material. UV-Vis spectroscopy showed maximum absorbance at 223 nm. The absorption maximum for photoluminescence was centered at 462 nm and that of cathodoluminescence was at 439.9 nm and 466.6 nm. Bulk of extracted silicon dioxide (SiO2) nano-powder from diatom frustules was used as a source material for preparing a high-quality crystalline film on P-type silicon (p-Si) by vapor-liquid-solid (VLS) method. The crystalline quality of the film was tested by X-ray diffraction (XRD) and the crystalline size obtained was 62 ± 2.4 nm. From scanning electron microscopic (SEM) investigation, the growth of a continuous film from diatom biosilica on p-Si substrate was revealed. The thickness of the as-grown SiO2 film was 22.2 ± 1.6 nm, obtained from spectroscopic ellipsometry (SE) study. The performances of fabricated Al/SiO2/Si metal-oxide-semiconductor capacitor were tested by measuring leakage current (~ 43 ± 8 × 10−11 A μm−2 at +2 V), capacitance-voltage, constant current (0.1 μA), and voltage stress (at − 2 V) for reliable gate dielectrics applications in MOS devices. Overall, the process was cost-effective and provides an alternative technique to design high-quality diatom-derived “Bio-SiO2 films” on p-Si substrate.

Effects of nitrogen, phosphorus, EDTA and sodium chloride on biomass and lipid accumulation of Chaetomorpha aerea

Abstract: Marine seaweeds or macroalgae are the excellent source of bioactive compounds like proteins, vitamins, carotenoids, dietary fibres and essential fatty acids. These essential fatty acids include both the saturated and unsaturated form. The lipid content of marine macroalgae is very low (1-5%) but under stress conditions they produce up to 30-40% [1]. The fatty acids of marine macroalgae generally have linear chains and even number of carbon atoms with one or more double bonds [2]. Macroalgae have been studied for long for the production of wide range of natural chemicals like agar, agarose, carrageenan and alginates. However, they have never been looked for lipids, as energy resource [1]. Microalgae have been considered for high lipid and used for biodiesel application several times [3-6]. Stress induced changes in lipid and fatty acids profile have also been discussed for long [7-11]. But very few reports are available on macroalgal lipid and fatty acids [12-14]. The effect of nitrate and phosphates on lipidomic and other biochemical compositions of the macroalga Ulva lactuca were studied by Kumari et al. [15]. They investigated the changes in polar lipids, chlorophyll and protein content when they cultured the alga in artificial sea nutrient (ASW) medium supplemented with nitrate and phosphate. Biochemical composition of eighteen marine macroalgae belonging to Chlorophyta, Phaeophyta and Rhodophyta were studied from Okha coast, Gulf of Kutch, India [16]. They studied varied quantities of bioactive compounds like total lipid, protein, carbohydrate, phenol and amino acids. Seasonal variations in fatty acid compositions of 51 macroalgae were studied from Gulf of Mannar, Marine Biosphere Reserve of Southeast coast of India [17]. Comparative accounts of fatty acid compositions of three marine macroalgae were also studied from the coastal region of South India [18]. In our previous study we have reported the effect of nutrient and other abiotic stresses on growth and lipid accumulation in Rhizoclonium africanum [13]. Effects of nitrogen, phosphorus, EDTA and sodium chloride on biomass and lipid accumulation of Chaetomorpha aerea