Carbon Dioxide Sequestering Ability of Bacterial Carbonic Anhydrase in a Mangrove Soil Microcosm and Its Bio-mineralization Properties
2019
Nathan, Vinod Kumar | Ammini, Parvathi
In this study, we attempt to prospect potential bacterial isolates from mangrove sediments of Mangalavanam, Kerala, India, with positive carbonic anhydrase (CA) activity to sequester carbon dioxide by calcium precipitation process. Fifteen bacterial colonies (M1–M15) isolated were screened for their carbonic anhydrase enzyme production potential based on p-nitro phenol acetate assay. Based on the secondary screening, M3 and M8 were identified as the most potential for carbonic anhydrase production. The specific activity of the partially purified CA enzyme from M3 and M8 were 44 U mg⁻¹ and 76 U mg⁻¹ respectively. The enzyme activity increased by 1.6-fold upon precipitation by acetone (80%). The potential isolate which higher CA production, M8 was identified as Bacillus altitudinis based on 16S rDNA sequencing. Soil microcosm was established to study carbonic anhydrase production and CO₂ sequestration ability of B. altitudinis M8 strain. B. altitudinis M8 strain could reduce CO₂ by 75 ± 0.12% in microcosm composed of sterilized soil with bacteria (SSB) and by 97 ± 0.34% in microcosm with sterile soil with enzyme (SSE). Hence, the application of enzyme was found to be more effective in removing CO₂ when compared to bacterial inoculum. To further understand the bio-mineralization ability of this microbial isolate, calcium precipitation assay was conducted. There was a reduction of 42.22 ± 0.23% of free calcium in the medium through calcite precipitation. The carbonic anhydrase-mediated calcium precipitation by B. altitudinis M8 strain could be effectively employed in the process of carbon dioxide sequestration.
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