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Development of a new and sustainable catalyst is necessary to the society for providing economical technology. Surface modification of nanometal oxides is one of the rapidly growing methods for developing a sustainable catalyst with attractive properties than their parent oxide. In this work, surface‐modified nickel ferrites have been carried out using 4,4′‐biphenyldisulfonic acid (BPDSA) as the linker. Thus, obtained modified material has been characterized using different techniques such as DLS, FT‐IR, TGA, XRD, VSM, and XPS. This well‐characterized, stable, robust, recyclable material offers a good conversion in the fatty acid, that is, oleic acid esterification in the presence of methanol in a short period of time (3.0 h). Based on the kinetic study in the oleic acid esterification, it fits in the pseudo first‐order kinetics, and activation energy was found to be 60.0 kJ/mol. Further, the potentiality of our catalyst was also tested in the transesterification of various raw materials like mustard oil, olive oil, almond oil, and neem oil. In addition, it provides an excellent conversion with microalgae lipid extraction for the production of biodiesel. The kinematic viscosity of the methyl oleate (biodiesel) has been found to be 5.0426 mm2/s at 25°C whereas the dynamic viscosity is 6.0511 mPa, which is nearly the same as biodiesel obtained from Dunaliella salina, microalgae lipid. [ABSTRACT FROM AUTHOR]

The present study was aimed at understanding the effects of heat stress on selected physiological and biochemical parameters of a model cyanobacterium, Anabaena PCC 7120 in addition to amelioration strategy using exogenous Ca2+. A comparison of the cells exposed to heat stress (0–24 h) in the presence or absence of Ca2+ clearly showed reduction in colony-forming ability and increase in reactive oxygen species (ROS) leading to loss in the viability of cells of Ca2+-deficient cultures. There was higher level of saturation in membrane lipids of the cells supplemented with Ca2+ along with higher accumulation of proline. Similarly, higher quantum yield (7.8-fold) in Ca2+-supplemented cultures indicated role of Ca2+ in regulation of photosynthesis. Relative electron transport rate (rETR) decreased in both the sets with the difference in the rate of decrease (slow) in Ca2+-supplemented cultures. The Ca2+-supplemented sets also maintained high levels of open reaction centers of PS II in comparison to Ca2+-deprived cells. Increase in transcripts of both subunits ((rbcL and rbcS) of RubisCO from Ca2+-supplemented Anabaena cultures pointed out the role of Ca2+ in sustenance of photosynthesis of cells via CO2 fixation, thus, playing an important role in maintaining metabolic status of the heat-stressed cyanobacterium. [ABSTRACT FROM AUTHOR]

Roles of nutrients and other environmental variables in development of cyanobacterial bloom and its toxicity are complex and not well understood. We have monitored the photoautotrophic growth, total microcystin concentration, and microcystins synthetase gene (mcyA) expression in lab-grown strains of Microcystis NIES 843 (reference strain), KW (Wangsong Reservoir, South Korea), and Durgakund (Varanasi, India) under different nutrient regimes (nitrogen, phosphorus, and boron). Higher level of nitrogen and boron resulted in increased growth (avg. 5 and 6.5 Chl a mg/L, resp.), total microcystin concentrations (avg. 1.185 and 7.153 mg/L, resp.), and mcyA transcript but its expression was not directly correlated with total microcystin concentrations in the target strains. Interestingly, Durgakund strain had much lower microcystin content and lacked microcystin-YR variant over NIES 843 and KW. It is inferred that microcystin concentration and its variants are strain specific. We have also examined the heterotrophic bacteria associated with cyanobacterial bloom in Durgakund Pond and Wangsong Reservoir which were found to be enriched in Alpha-, Beta-, and Gammaproteobacteria and that could influence the bloom dynamics. [ABSTRACT FROM AUTHOR]

The effects of exogenously added CaCl 2 (0.25 mM) on photopigments, photosynthetic O 2 -evolution, antioxidative enzyme activity, membrane damage, expression of two heat shock genes ( groEL and groES ) and apoptotic features in Anabaena 7120 under heat stress (45 °C) for up to 24 h were investigated. Heat stress lowered the level of photopigments; however, Ca 2+ ­-supplemented cultures showed a low level reduction in Chl a but induced accumulation of carotenoids and phycocyanin under heat stress. Photosynthetic O 2 -evolving capacity was maintained at a higher level in cells from Ca 2+ -supplemented medium. Among the antioxidative enzymes, superoxide dismutase activity was unaffected by the presence or absence of Ca 2+ in contrast to increases in catalase, ascorbate peroxidase and glutathione reductase activities in cells grown in Ca 2+ -supplemented medium. Lower levels of lipid peroxidation were recorded in Anabaena cells grown in Ca 2+ -supplemented medium in comparison to cells from Ca 2+ ­-deprived medium. Target cells grown in Ca 2+ -deprived medium developed apoptotic features in the early stages of heat shock, while Ca 2+ application seemed to interfere with apoptosis because only a few cells showed such features after 24 h of heat exposure, indicating a role for Ca 2+ in maintaining cell viability under heat stress. There was also continuous up regulation of two important heat shock genes (groEL and groES) in Ca 2+ -supplemented cultures, exposed to heat shock, again indicating a role for Ca 2+ in stress management. [ABSTRACT FROM AUTHOR]