Economic growth causes a significant increase in greenhouse gas emissions, the main representative of which is carbon dioxide (CO2). International agreements aim to reduce CO2 emissions and limit the increase in global temperature to 1.5 °C by 2050. For this, the development of biotechnological processes using microorganisms capable of capturing CO2 is a good alternative for reducing of CO2 emissions and complete use of biomass. Some microorganisms are capable of performing a mixotrophic metabolism, in which there is concomitant assimilation of organic and inorganic carbon. Among these, Clostridium beijerinckii ATCC 35702 was reported as being able to assimilate CO2 during glucose fermentation. Possible CO2 assimilation pathways in this microorganism are: 1) Wood-Ljungdahl pathway; 2) via carbonic anhydrase enzyme and 3) by the reverse mechanism of pyruvate-ferredoxin oxidoreductase enzyme. Possibly, C. beijerinckii Br21, a strain isolated in our laboratory, is also capable of carrying out this type of metabolism. This hypothesis was formulated after recurrently obtaining carbon recovery values above 100% when compared to stoichiometry. It was verified that the Br21 strain also contains the necessary enzymatic machinery for the capture of CO2, just as the ATCC 35702 strain. Thus, this investigation aims to prove the capture of CO2 by C. beijerinckii Br21, as well as to increase the efficiency of this process by optimizing cultivation conditions and genetic engineering. With this, the aim is to achieve one of the objectives described by the UN, "Take urgent action to combat climate change and its impacts", by developing a more robust microorganism for industrial application, with the ability to use renewable resources and capture CO2.
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