CO2 capture using limestone for cultivation of the freshwater microalga Chlorella sorokiniana PAZ and the cyanobacterium Arthrospira sp. VSJ.

The present study reports a process wherein CO2 is captured in the form of bicarbonates using calcium oxide and photosynthetically fixed into biomass. Microalgal cultures viz. Chlorella sorokiniana PAZ and Arthrospira sp. VSJ were grown in the medium containing bicarbonates. The rate of bicarbonate utilization by C. sorokiniana PAZ was higher when CO2 trapped in the presence of 2.67mM calcium oxide than in the presence of 10mM sodium hydroxide and with direct addition of 10mM sodium bicarbonate. For Arthrospira sp. VSJ the bicarbonate utilization was 92.37%, 88.34% and 59.23% for the medium containing CaO, NaOH and NaHCO3, respectively. Illumination of photosynthetically active radiation (PAR)+ultraviolet A radiation (UVA) enhanced the yield of C. sorokiniana PAZ and Arthrospira sp. VSJ by 1.3 and 1.8 folds, respectively. FTIR analysis revealed elevation in the biosynthesis of specific metabolites in response to the UVA exposure.

Scrutinizing the influence of UV radiation on adsorption behavior of zinc metal on marine diatom Nitzschia sp. BDU DD 002.

The present study is an investigation into the adsorption of zinc metal on marine diatom Nitzschia sp. under the influence of ultraviolet radiation to reveal the possible role of radiation in metal biomineralization. Nitzschia sp. was isolated from marine habitat and gradually acclimatized to UVA, UVB, and zinc (30 mg/L). The culture was subjected to various concentrations of zinc (5, 10, 15, 20 mg/L) with an artificial exposure of PAR, PAR + UVA, and PAR + UVB radiation. The adsorption isotherm models were applied for validating the hypothesis stating the association of zinc adsorption with exposure to ultraviolet radiation. Altered functional groups on the surface were observed in the FTIR spectra along with changes in antioxidant activity, superoxide dismutase activity, pigment and protein contents due to increased zinc concentration and ultraviolet radiation. Scanning electron micrographs (SEM-EDAX) supported the microscopic morphology of adsorbed metals.