Biosequestration of carbon dioxide using carbonic anhydrase from novel Streptomyces kunmingensis

The increase in the atmospheric concentrations of carbon dioxide due to anthropogenic interventions has led to several undesirable consequences, notably global warming and related changes. Avoidance of and/or removal of carbon dioxide will result in the reduction of global warming. Biosequestration of carbon by using carbonic anhydrase (CA) as biocatalyst is one of most effective approaches. In the present study, actinobacterial cultures isolated from bamboo (Bambusa vulgaris) rhizosphere were screened for the production of carbonic anhydrase enzyme. The strain BS19 which showed promising CA production was selected as the potential strain. Strain BS19 was identified as Streptomyces kunmingensis based on the phenotypic and molecular characteristics. In submerged fermentation, strain BS19 produced 214.21 IU/ml of CA enzyme. The molecular mass of the CA was determined as 45 ± 2 kDa. The production of CA was found to be optimal at pH 7.0 and at temperature of 28 °C. The full length periplasmic CA gene was successfully amplified from S. kunmingensis BS19. Biomimetic sequestration of carbon was detected and quantified through CaCO₃ precipitation method. Further, the CA of BS 19 was successfully used to mineralize CO₂ present in motorbike exhaust, which has a similar composition to that of flue gas. The well-defined rhombohedral calcite crystals formed in the mineral carbonation reaction was observed through SEM analysis. The findings of this study clearly indicated that Streptomyces kunmingensis BS19 isolated from bamboo rhizosphere is a promising candidate for the production of carbonic anhydrase which deserves the potential for CO₂ sequestration.