Improved CO2 fixation with Oscillatoria sp. in response to various supply frequencies of CO2 supply

•Marine microalgae Oscillatoria sp. showed the tolerance capability of pure CO2.•Oscillatoria sp. grown in ASN III media along with the intermittent supply of pure CO2 resulted in increased biomass yield.•Increased supply frequency has an impact on pH variation and resulted in higher specific growth rate.•Supply frequency of CO2 has an impact on improved biomass yield, carbon fixation, carbon utilisation and calorific value of the biomass.

Sequestration of CO2 by microalgae is one of the technically viable options to control the CO2 emission. CO2 sequestration by microalgae through photosynthesis also results in large quantity of biomass production with considerable fuel properties. Different types of micro algal species have got CO2 tolerance to a different level. This work focuses on the tolerance capability of Oscillatoria sp. for 100% CO2, bubbled into the ASN III media. CO2 supply was given at a flow rate of 300 ml/min for 15 min. 12:12 h of light to dark cycle was followed.CO2 supply was varied from one to three times a day during the light period. An increasing trend of biomass growth was observed with increased supply frequency of CO2. An increase of biomass yield of 44.7%, CO2 fixation of 64.2% and calorific value of 17.6% was observed corresponding to the three times supply frequency of CO2, compared with the control. Ultimate analysis, stoichiometric analysis and molecular weight of microalgae grown in control and pure CO2 (100%) gas were compared. Growth of microalgae obtained at various supply frequencies of CO2 were fitted with logistic model with a correlation coefficient of 0.98. The present studies indicated that the Oscillatoria sp. was able to sustain in pure CO2(100%) gas and may be considered as the species for converting the emissions from the distilleries to energy.