Carbon dioxide fixation by reversible pyrrole-2-carboxylate decarboxylase and its application

Inducible pyrrole-2-carboxylate decarboxylase from Bacillus megaterium PYR3910 catalyzes the decarboxylation of pyrrole-2-carboxylate to stoichiometric amounts of pyrrole and CO2. A unique feature of the homodimeric enzyme is its requirement for an organic acid such as acetate, propionate, butyrate or pimelate. A catalytic mechanism including a cofactor function of the organic acid was proposed. Due to an equilibrium constant of 0.3-0.4 M, the enzyme also catalyzes the reverse carboxylation of pyrrole after the addition of bicarbonate. For the synthesis of pyrrole-2-carboxylate, the reverse reaction was optimized and the equilibrium shifted towards the carboxylate. The product yield was 230 mM (25.5 g/l) pyrrole-2-carboxylate from 300 mM pyrrole in a batch reaction and 325 mM (36.1 g/l) from 400 mM pyrrole in a fed batch reaction, using both whole cells and the purified enzyme in a pH 8.0 reaction mixture with bicarbonate saturation of 1.9 M. (C) 2001 Elsevier Science B.V. All rights reserved.