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Gradual rise in levels of atmospheric carbon dioxide (CO2) due to burning of fossil fuels has become a matter of environmental concern in the recent years. In this alarming situation capturing CO2 and storing it to restrict its release to the atmosphere could be an attractive approach toward mitigation. Photosynthesis has been recognized as the most sustainable means to arrest CO2 from the atmosphere and microalgae; a photosynthetic microorganism has been identified as the potential sequestering candidate with the highest carbon fixing capabilities. Cyanobacteria and algae have developed their own exclusive editions of photosynthetic carbon concentrating mechanisms (CCMs) to aid ribulose‐1,5‐bisphosphate carboxylase/oxygenase (RuBisCO) in efficient CO2 capture. Carbonic anhydrase (CA), a zinc‐containing metallo‐enzyme has been observed to play a key role in the CCM by catalysing the reversible hydration of CO2 into bicarbonate and a proton thereby helping in fixation of atmospheric CO2. This review gives an account of the importance of the different types of CA enzymes along with its locations, mechanism of action and the various studies on biosequestration of CO2 through microalgae. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 1605–1615, 2016

Selection of suitable strain of microalgae is the crucial factor for large-scale production of algae-based products. Efforts have been made here for isolation, identification and biochemical characterization of five microalgae strains collected from Tripura (a small state in north-eastern region of India). Two Chlorococcum sp. (NITAAP008 and NITAAP019) demonstrate their high lipid (15-24%), equal amounts of carbohydrate and protein (35-40%), with specific growth rate of 0.13 day À1 . These strains are potential resource for biofuel production. After lipid extraction, remaining biomass can be used as source of carbohydrate for the production of other biofuels. One isolated strain is identified as Chlorella sp. (NITAAP009) and shows 22-33% carbohydrate, 41-50% protein and 5% chlorophyll with specific growth rate of 0.125 day À1 . Another Chlorella sp. (NITAAP011) isolated from lake area exhibits significant chlorophyll (5-6.4%), 30-50% carbohydrate, 48-60% protein and low lipid (1-10%) with lower specific growth rate (0.10 day À1 ). Both strains are having industrial competence for chlorophyll production due to their synthesizing ability of significant amount of chlorophyll (5-6.4%). The last one, Korshikoviella sp. (NITAAP017), has 15-18% lipid, 22-34% carbohydrate, 30-43% protein and 3-4% chlorophyll with specific growth rate of 0.12 day À1 and can be used for food supplement production or lipid synthesis.

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Background: : North east region of India is well known as biodiversity hotspot with endemic flora and fauna. Organisms belonging to the cyanobacterial species are commonly known as blue green algae and are found in diverse categories in the environment of north-east India. Potentials of these cyanobacterial species are mostly unexplored. Present study aimed to isolate, identify and evaluate the potential cyanobacterial strains for the sustainable producers of biomolecules with agricultural, therapeutic and industrial significance. Methods:: Growth and biochemical characterization were performed with the isolated cyanobacterial species to investigate the growth kinetics, cellular pigments (carotenoid, phycobiliprotein and chlorophyll), protein, carbohydrate and lipid content. Results:: Three Phormidium sp., one Oscillatoria sp., and one Microcoleus sp. were isolated from the Tripura state (North-east region of India). Results revealed that isolated Oscillatoria sp. has high lipid (~20%), protein (~40%), and carbohydrate (~30%) yield. Further, two isolated Phormidium sp., produced significant amount of carotenoids (~23 mg/gm dry biomass), phycobiliprotein (~20-25%) and high protein (~55%). Microcoleus sp. produced 62% carbohydrate and 20% phycobiliprotein with significant amount of carotenoids (~17 mg/gm dry biomass). Conclusion:: Isolated Oscillatoria sp. is the promising resource for lipid and nutritional supplement due to high accumulated primary metabolites. Two Phormidium sp., can be used as animal and human nutritional food supplement and also can be further investigated for pigment production at industrial scale. Isolated Microcoleus sp. is the potential resource of carbohydrate and pigment. Isolated cyanobacterial strains are identified as viable candidates for the industrial production of biomass as well as other value added biomolecules.