Poly(3-hydroxybutyrate)-depolymerase from Pseudomonas lemoignei: Catalysisof esterifications in organic media

Lipase catalysis in nonaqueous media is recognized as a powerful tool in or ganic and more recently polymer synthesis. Even though none of the currentl y known polyhydroxyalkanoate (PHA) depolymerases have lipase activity, they do have a catalytic center that resembles that of lipases. Motivated by th e above, the potential of using the poly(3-hydroxybutyrate), PHB, depolymer ase from Psuedomonas lemoignei in organic media to catalyze eater-forming r eactions was investigated. The effect of different organic solvents (benzen e-d(6), cyclohexane-d(12), and acetonitrile-d(3)) on the activity of the PH B-depolymerase toward propylation of L-lactide was studied. A significant d ifference in the catalytic rate was observed as a function of solvent polar ity. The selectivity of the PHB-depolymerase (P. lemoignei) to catalyze the propylation of a series of different; lactones including epsilon -caprolac tone, delta -butyrolactone, gamma -butyrolactone, and D, L, meso, and racem ic lactides has been studied with the PHB-depolymerase (P. lemoignei) in or ganic solvents. Important differences in the reactivity of these lactones, as well as selective hydrolysis of stereochemically different linear lactic acid dimers, were observed. Moreover, the ability of the PHB-depolymerase to catalyze the solventless polymerization of epsilon -caprolactone and tri methylene carbonate was investigated.