The concentration of carbon dioxide, a major greenhouse gas, has been increasing in the atmosphere due to various anthropogenic activities. This review aims at summarizing different organisms, including eukaryotes and prokaryotes that have the ability to assimilate CO2. In addition, the metabolic pathway via which an organism sequesters CO2 is explained in brief. The adaptations of different organisms for efficient CO2 sequestration have also been explained in the current review. An important advantage of applying biological systems to manage CO2 is that it synthesizes industrially useful byproducts such as bioplastics, medicinal compounds, and biofuels. Hence, this review helps in understanding diverse biological systems that can be utilized to develop a sustainable technology to mitigate CO2 at an industrial level. © 2018 American Institute of Chemical Engineers Environ Prog, 38: 127–136, 2019

Methylene blue (MB) commonly found in the textile industry effluent has been chosen as a model dye to investigate bioremediation using Bacillus subtilis MTCC 441. Both free cells and calcium alginate immobilized cells have been used to remove MB from the effluent. The operating variables of initial concentration of dye (20-60 mg/L), inoculum size (4-8%) and temperature (25-35 °C) have been varied judiciously during the kinetic study in a batch contactor. A maximum removal of 91.68% is obtained when 20 mg/L MB solution was inoculated with 8% inoculum and cultured for 6 h at 30 °C. Continuous removal of MB has been studied in a fixed bed contactor using immobilized cells as packing materials. Influent concentration (10-30 mg/L) was varied and breakthrough parameters have been determined. With increase in influent concentration from 10 mg/L to 30 mg/L, percentage removal of dye decreases from 72.44% to 49.62%.

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In the present work, carbon dioxide (CO2) fixation potential of bacteria and cyanobacterial consortium was studied and compared. Serratia marcescens NCIM 2078, the chemolithotrophic bacteria, which was used in the present study, was collected from National Collection of Industrial Microorganisms (NCIM), Pune, India. The cyanobacterial consortium used was Leptolyngbya subtilis and Planktothrix agardhii. It was collected from East Kolkata Wetland (EKW), Kolkata, India, a Wetland of International Importance. Serratia marcescens NCIM 2078 and the consortium Leptolyngbya subtilis and Planktothrix agardhii were cultivated with 10%, 20%, and 30% CO2. These two microbial agents could grow at 30% CO2 and showed optimum growth at CO2 concentration of 10%. The maximum biofixation of CO2 observed was 98.32% and 94.06% for Serratia marcescens NCIM 2078 and for the consortium of Leptolyngbya subtilis and Planktothrix agardhii at 10% of CO2 concentration. Carbon dioxide showed toxic effects on both the microorganisms at high concentration and the lipid content also decreased with increased CO2 concentration. The present results indicate the efficacy of these two microbes for mitigating CO2 in the flue gases. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 1594–1600, 2018

Sequestration of CO2 using microalgae is one of the imperative, cost effective and environment‐friendly processes for carbon sequestration and for production of biomass. In the present study, a cyanobacterial consortium was used for the sequestration of CO2 at diverse initial CO2 concentrations (5–30%), pH of the medium (7–11) and inoculum sizes (5–12.5%). The cyanobacterial consortium showed sustainability in growth upto 30% CO2. The overall CO2 fixation capacity was found as 0.0692 and 0.071 mol CO2/g algae at 15% CO2, pH 9 and at 10% and 12.5% inoculum, respectively, after 14 days. Characterization of dry biomass before and after CO2 sequestration was done using Fourier Transform Infrared spectroscopy. Various algorithm of artificial neural network (ANN) model and a number of activation functions were tried to arrive at best ANN model for such process. Finally, Particle swarm optimization was used for optimization of input variables for maximum sequestration of CO2.

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