Research article Sequestration of carbon dioxide and production of biomolecules using cyanobacteria Ganta Upendar a , Sunita Singh b , Jitamanyu Chakrabarty b , Kartik Chandra Ghanta a , Susmita Dutta a, * , Abhishek Dutta c a Department of Chemical Engineering, National Institute of Technology Durgapur, Durgapur, 713209, India b Department of Chemistry, National Institute of Technology Durgapur, Durgapur, 713209, India c Faculteit Industri€ ele Ingenieurswetenschappen, KU Leuven, Campus Groep T Leuven, Leuven, B-3000, Belgium article info Article history: Received 16 September 2017 Received in revised form 1 April 2018 Accepted 6 April 2018 Keywords: Carbon dioxide Sequestration Synechococcus sp. NIT18 Biomolecules Empirical modeling abstract A cyanobacterial strain, Synechococcus sp. NIT18, has been applied to sequester CO 2 using sodium car- bonate as inorganic carbon source due to its efficiency of CO 2 bioconversion and high biomass pro- duction. The biomass obtained is used for the extraction of biomolecules - protein, carbohydrate and lipid. The main objective of the study is to maximize the biomass and biomolecules production with CO 2 sequestration using cyanobacterial strain cultivated under different concentrations of CO 2 (5e20%), pH (7 e11) and inoculum size (5e12.5%) within a statistical framework. Maximum sequestration of CO 2 and maximum productivities of protein, carbohydrate and lipid are 71.02%, 4.9 mg/L/day, 6.7 mg/L/day and 1.6 mg/L/day respectively, at initial CO 2 concentration: 10%, pH: 9 and inoculum size: 12.5%. Since flue gas contains 10e15% CO 2 and the present strain is able to sequester CO 2 in this range, the strain could be considered as a useful tool for CO 2 mitigation for greener world. © 2018 Elsevier Ltd. All rights reserved. 1. Introduction The increase in carbon dioxide (CO 2 ) concentration in the at- mosphere is mainly due to the burning of fossil fuels such as pe- troleum, coal and natural gases, which results in global warming and climate change (Brennan and Owende, 2010; Chi et al., 2011; Anjos et al., 2013; Yadav et al., 2015). The anthropogenic activities such as extreme utilization of fossil fuels, industrialization and deforestation have led to abnormal increase in greenhouse gas emissions (Yadav et al., 2015). Coal-fired power plants are the major sources of CO 2 in the atmosphere (Langely et al., 2012; Roberts et al., 2015) with flue gases releasing from such thermal power plants being responsible for greater than 7% of the total world CO 2 discharges (Vasumathi et al., 2012). In recent times, the concen- tration of CO 2 in the atmosphere has reached an upsetting level of 400 ppm due to human activities and by natural processes (Tans, 2015). It is well imagined that the CO 2 levels more than 450 ppm could be dangerous to global environment (Hansen et al., 2007). As of now, CO 2 is responsible for approximately half of total global warming (Wilbanks and Fernandez, 2013). For this reason, CO 2 reduction has become one of the most crucial topics of research around the world. A number of physico-chemical and biological methods have been employed so far for CO 2 mitigation, among which biological sequestration using cyanobacteria is found to be one of the most effective approach for CO 2 mitigation (de Morais and Costa, 2007a; Wang et al., 2008; Kumar et al., 2011). Uses of cyanobacterial spe- cies have been considered as one of the promising methods for the sequestration of CO 2 and serves as a feedstock for biofuel produc- tion, aiming towards a replacement of fossil fuels (Anjos et al., 2013). The main reason for choosing cyanobacteria for CO 2 sequestration is due to its photosynthetic efficiency of CO 2 bio- conversion, high biomass production, accumulation of bio- molecules and other non-fuel related products (Xie et al., 2014; Cheah et al., 2015). It is well known that the growth rate of microalgae/cyanobacteria is very fast and the biofixation efficiency is 10e50 times higher than terrestrial plants (Li et al., 2008; Wang et al., 2008; Yadav et al., 2015). After biofixation of CO 2 , the microalgal/cyanobacterial biomass produced has significant amounts of proteins, carbohydrates, lipids and other valuable compounds, such as vitamins, which can further be used as active ingredients in food and feed supplements or as precursor for * Corresponding author. E-mail address: susmita_che@yahoo.com (S. Dutta). Contents lists available at ScienceDirect Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman https://doi.org/10.1016/j.jenvman.2018.04.031 0301-4797/© 2018 Elsevier Ltd. All rights reserved. Journal of Environmental Management 218 (2018) 234e244