Ashish Bhatnagar

Biomass Production Potential of a Wastewater Alga Chlorella vulgaris ARC 1 under Elevated Levels of CO2 and Temperature

The growth response of Chlorella vulgaris was studied under varying concentrations of carbon dioxide (ranging from 0.036 to 20%) and temperature (30, 40 and 50°C). The highest chlorophyll concentration (11 μg mL–1) and biomass (210 μg mL–1), which were 60 and 20 times more than that of C. vulgaris at ambient CO2 (0.036%), were recorded at 6% CO2 level. At 16% CO2 level, the concentrations of chlorophyll and biomass values were comparable to those at ambient CO2 but further increases in the CO2 level decreased both of them. Results showed that the optimum temperature for biomass production was 30°C under elevated CO2 (6%). Although increases in temperature above 30°C resulted in concomitant decrease in growth response, their adverse effects were significantly subdued at elevated CO2. There were also differential responses of the alga, assessed in terms of NaH14CO3 uptake and carbonic anhydrase activity, to increases in temperature at elevated CO2. The results indicated that Chlorella vulgaris grew better at elevated CO2 level at 30°C, albeit with lesser efficiencies at higher temperatures.

Interactive biosorption by microalgal biomass as a tool for fluoride removal

Maximum biosorption of Ca2+ was at 50 mg Ca2+ l−1 with both Anabaena fertilissima (2.8 mg Ca2+ g−1 dry wt) and Chlorococcum humicola (4.4 mg g−1). Such Ca2+-treated biomasses, accumulated, respectively, 7 mg F g−1 DW from an aqueous solution of 10 mg F l−1 and 4.5 mg F g−1 DW from 15 mg F l−1. Data for both Ca2+ and F− biosorption fitted the Langmuir adsorption isotherm indicating monolayer adsorption at a constant energy.

Effect of cell rupturing methods on the drying characteristics and lipid compositions of microalgae.

This paper investigated the effect of cell rupturing methods on the drying characteristics and the lipid compositions of a green algae consortium grown in an open raceway pond. The ruptured microalgae samples obtained from French press, autoclave and sonication methods were used for conducting thin layer drying experiment at four drying temperatures (30, 50, 70 and 90 °C). The rate of moisture removal at each drying condition was recorded until no change in moisture loss. A typical drying curve for a microalgae consortium indicated that the rate of drying was limited by diffusion. Among three drying models (Newton, Page and Henderson-Pabis) used to fit the drying data, Page model fitted well on the experimental drying data with a coefficient of determination (R(2)) of 0.99. Solvent extraction of French press ruptured cells produced the highest total lipid yield with no significant change in lipid compositions.

Exopolymers from Tolypothrix tenuis and three Anabaena sp. (Cyanobacteriaceae) as novel blood clotting agents for wound management

Rapid initiation of clotting is critical to trauma patients. In the present study exopolymers (EPs) from four desert cyanobacteria including Tolypothrix tenuis and three species of Anabaena have been discovered as potential hemostatic biomaterials. The EPs showed reduction in activated partial thromboplastin time (APTT) and prothrombin time (PT) by 16-41% and 12-65%, respectively. Besides hastening blood clotting, the EPs could absorb 7.1-25.9 g H₂O g(-1) EP and displayed 7.1-18.1% hydrophobicity. They were noncytotoxic and biodegradable. The EP from Anabaena sp. showed strong antibacterial activity against E. coli, S. aureus and B. licheniformis. These results suggest that cyanobacteria, the microscopic phototrophs growing rapidly over simple mineral medium could prove to be a novel source of affordable hemostatic dressings for the traumatic wounds in underdeveloped and developing countries. Compositional analysis of the EPs showed them to be consisting of mainly carbohydrate (17-50%), protein (4.4-7.2%), uronic acid (4.7-9.5%) and sulphate (0.6-6.6%). Their viscometric molecular weight ranged from 539 to 3679 kDa. They were further characterized using GC-MS and FTIR.

Carbon and Nitrogen Fixation by Anabaena fertilissima under Elevated CO2 and Temperature

ABSTRACT We studied the growth of Anabaena fertilissima under graded CO2 and temperature conditions to assess its suitability as a CO2 scavenger for carbon recycling. A. fertilissima reached maximum growth at 6% CO2, but growth declined above this CO2 level; yet, at no CO2 concentration growth was less than that at ambient CO2. High temperature (>30°C) reduced growth of the cyanobacterium, but presence of elevated (6%) CO2 lessened the intensity of that reduced growth. High temperature also reduced biomass, pigments, total protein, and nitrogen fixation, but elevated CO2 significantly moderated this negative effect. Elevated CO2 reduced 14CO2 uptake by 50% at 30°C and >44% at higher temperatures compared to uptake at ambient CO2 at 30°C. Similarly, carbonic anhydrase activity also showed inhibition at high CO2.

Microbial Diversity in Soil, Sand Dune and Rock Substrates of the Thar Monsoon Desert, India

A culture-independent diversity assessment of archaea, bacteria and fungi in the Thar Desert in India was made. Six locations in Ajmer, Jaisalmer, Jaipur and Jodhupur included semi-arid soils, arid soils, arid sand dunes, plus arid cryptoendolithic substrates. A real-time quantitative PCR approach revealed that bacteria dominated soils and cryptoendoliths, whilst fungi dominated sand dunes. The archaea formed a minor component of all communities. Comparison of rRNA-defined community structure revealed that substrate and climate rather than location were the most parsimonious predictors. Sequence-based identification of 1240 phylotypes revealed that most taxa were common desert microorganisms. Semi-arid soils were dominated by actinobacteria and alpha proteobacteria, arid soils by chloroflexi and alpha proteobacteria, sand dunes by ascomycete fungi and cryptoendoliths by cyanobacteria. Climatic variables that best explained this distribution were mean annual rainfall and maximum annual temperature. Substrate variables that contributed most to observed diversity patterns were conductivity, soluble salts, Ca2+ and pH. This represents an important addition to the inventory of desert microbiota, novel insight into the abiotic drivers of community assembly, and the first report of biodiversity in a monsoon desert system.

Antioxidant and iron-chelating activities of cyanobacterial exopolymers with potential for wound healing

Progress of wound healing is critically dependent on the balance between oxidants and antioxidants at the wound site, and transition metals such as iron can exacerbate ROS generation. In the present study, cyanobacterial exopolymers from three strains of Anabaena and Tolypothrix tenuis have been characterized for their antiradical and Fe2+-chelating activity. All the four exopolymers exhibited antioxidant activities against O2·, H2O2, OH·, and NO·, with the exopolymer from Anabaena oryzae showing strong inhibition of NO· and ·OH radicals followed by that from Anabaena anomala. Correlation analysis of antioxidant activities and sulphate, uronic and phenolic content of the exopolymers showed a strong correlation of sulphate content to superoxide scavenging and activity against nitric oxide radicals. H2O2 scavenging was related to the presence of phenolics in the preparation which also contributed to the reducing power. Iron chelation had a strong bearing upon the overall reducing power and superoxide control.