SHORT COMMUNICATION Influence of carbon-dioxide on the growth of Spirulina sp. (MCRC-A0003) isolated from Muttukadu backwaters, South India M. Sivakumar • R. Ranjith Kumar • V. Shashirekha • S. Seshadri Received: 28 February 2013 / Accepted: 8 June 2014 Ó Springer Science+Business Media Dordrecht 2014 Abstract Growth of Spirulina sp. (MCRC-A0003), a cyanobacterium, was evaluated under different concentra- tions of carbon-dioxide (CO 2 ) (4–50 %) in a closed glass photobioreactor. Although significant CO 2 utilization by the cyanobacterial strain was observed up to 50 % con- centration, complete utilization was observed only at 4, 10 and 20 % concentrations on 3rd, 6th and 8th day respec- tively. However, considerable reduction was witnessed in reactors containing 30–50 % CO 2 only between 6th and 9th day. A corresponding increase in the biomass and primary metabolites like chlorophyll-a, carbohydrate and protein were observed. Biomass productivity of Spirulina in reac- tors sparged with 4, 10 and 20 % CO 2 were 13.7, 43 and 44 % more than that in control reactor without CO 2 . While CO 2 increased the levels of primary metabolites in the cyanobacterial cells, it was quite prominent in 10 % CO 2 concentration with the chlorophyll-a, carbohydrate and protein contents were 64, 183 and 626 mg g -1 respec- tively. While 10 and 6.6 % increase were noticed in chlorophyll-a and protein, 17 % increase in carbohydrate levels was observed in Spirulina cells, which could be attributed to the conversion of CO 2 to carbohydrate by the cyanobacterium. Keywords Carbon-dioxide  Spirulina  Photobioreactor  Primary metabolites Introduction With increased atmospheric carbon-dioxide (CO 2 ) levels, the issue of global warming has become a major focus in the environmental agenda. Among many attempts to reduce the quantity of CO 2 in the atmosphere, biotechnology of using microalgae in a photobioreactor has extensively been studied since the beginning of the 1990’s. With the biological approach, CO 2 is converted into algal/cyanobacterial biomass and other valuable metabolites such as pigments, proteins and vitamins, which in turn can be used as feed additives, nutri- tional supplements, food colorants, pharmaceutical and nu- traceutical purposes besides use as biofertilizers and substrates for biofuel production (Packer 2009; Ho et al. 2011). Many microalgae and cyanobacteria belonging to genus Botryococcus, Cyanidium, Scenedesmus, Chlorococcum, Euglena, Chlorella, Eudorina, Phaeodactylum, Dunaliella, Synechococcus, Spirulina etc. have been evaluated for CO 2 sequestration (Hanagata et al. 1992; Nagase et al. 1998; Michele and Jorge 2007; Suali and Sarbatly 2012; Yahya et al. 2013). Spirulina platensis, popular filamentous cyanobacterial species in biotechnology, has been pro- duced commercially all over the world for its high protein content (up to 70 %), pigments (phycocyanin), essential fatty acids, vitamin B 12 and minerals (Becker 1981). High pH (9.5–9.8), which effectively inhibits the contamination by other algae, is the key factor for large-scale outdoor cultivation of Spirulina sp. (Hu 2007). Most of the studies on CO 2 mitigation using cyano- bacteria and other microalgae provide little information on the performance of ecotypes and their physiological M. Sivakumar  R. Ranjith Kumar  V. Shashirekha  S. Seshadri (&) Shri AMM Murugappa Chettiar Research Centre (MCRC), Taramani, Chennai 600 113, India e-mail: tsvisesh@yahoo.co.in; seshadris@mcrc.murugappa.org Present Address: R. Ranjith Kumar Department of Plant Biology and Plant Biotechnology, Shree Chandraprabhu Jain College, Minjur, Chennai, India 123 World J Microbiol Biotechnol DOI 10.1007/s11274-014-1688-y