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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