NOVELTY - Recombinant polypeptide comprising an amino acid sequence, is new, where the amino acid sequence has carbonic anhydrase activity of greater than 25% when incubated for 30 minutes or longer at a pH of 8-10.5, the amino acid sequence has a higher thermostability and/or melting temperature at a higher ionic strength, and the amino acid sequence is at least 70% identical to the amino acid sequence of SEQ ID NO: 3, SEQ ID NO: 28, SEQ ID NO: 43, SEQ ID NO: 53, SEQ ID NO: 64, SEQ ID NO: 80, SEQ ID NO: 130, or SEQ ID NO: 136.    USE - The polypeptide is useful for extracting carbon dioxide from a carbon dioxide-containing medium, where the carbon dioxide-containing medium is a gas comprising a flue gas, raw natural gas, syngas, hydrogen gas, or biogas, a liquid, or a multi-phase mixture, and the carbon dioxide-containing medium is a byproduct of combustion or fermentation (all claimed). The polypeptide is useful: as an independent carbon dioxide extraction catalyst; for recycling carbon dioxide emissions from a fossil-fuel power plant into carbonated species; and for accelerating the rate of absorption and reaction of carbon dioxide into the aqueous phase of a carbonate solution to form bicarbonate.    ADVANTAGE - The polypeptide has increased thermostability and increased melting temperature at a higher ionic strength.    DETAILED DESCRIPTION - Recombinant polypeptide comprising an amino acid sequence, is new, where the amino acid sequence has carbonic anhydrase activity of greater than 25% when incubated for 30 minutes or longer at a pH of 8-10.5, the amino acid sequence has a higher thermostability and/or melting temperature at a higher ionic strength, and the amino acid sequence is at least 70% identical to the amino acid sequence of SEQ ID NO: 3 (comprising a 252 amino acid sequence fully defined in the specification), SEQ ID NO: 28 (comprising a 245 amino acid sequence fully defined in the specification), SEQ ID NO: 43 or 64 (comprising a 251 amino acid sequence fully defined in the specification), SEQ ID NO: 53 (comprising a 205 amino acid sequence fully defined in the specification), or SEQ ID NOs: 80, 130 or 136 (comprising a 219 amino acid sequence fully defined in the specification). INDEPENDENT CLAIMS are included for:    (1) a composition-1 comprising the recombinant polypeptide and a carbon dioxide-containing medium;    (2) an isolated nucleic acid encoding the recombinant polypeptide;    (3) an expression vector comprising the isolated nucleic acid in operable combination with a regulatory sequence;    (4) a host cell comprising the expression vector;    (5) a composition-2 comprising the host cell and a culture medium;    (6) producing a carbonic anhydrase, comprising culturing the host cell in a culture medium, under suitable conditions to produce the carbonic anhydrase;    (7) a composition-3 comprising the carbonic anhydrase produced in accordance with the method in supernatant of the culture medium;    (8) a method-1 for extracting carbon dioxide from a carbon dioxide-containing medium, comprising contacting the carbon dioxide-containing medium with the polypeptide to yield a medium reduced in carbon dioxide; and    (9) a method-2 for regulating pH of a medium containing one or both of carbon dioxide and bicarbonate, comprising contacting the medium with the polypeptide to yield a medium with an altered pH.