Crystallinity-Induced Biodegradation of Novel [(R,S)-β-Butyrolactone]-b-pivalolactone Copolymers

Abstract

Novel model block copolymers of (R,S)-β-butyrolactone with pivalolactone (PVL) are prepared in order to define the effect of crystalline domains provided by poly(pivalolactone) on the biodegradability of atactic poly(β-butyrolactone), a-PHB. The “living” a-PHB is synthesized from racemic β-butyrolactone, in the presence of potassium alkoxide/18-crown-6 complex, and such a living polymer is applied for polymerization of PVL, yielding block copolymers, a-PHB-b-PPVL, of tailored molecular weight and composition. The copolymers contain an amorphous phase with T g = 5 °C, associated with the a-PHB block, and a high melting crystalline phase, whose amount increases with PPVL content. Films of copolymers containing 9 (PVL9), 17 (PVL17), and 23 mol % of PPVL (PVL23) are exposed to PHB-depolymerase A from Pseudomonas lemoignei (37 °C, Tris−HCl buffer pH = 8). While plain a-PHB does not biodegrade, the biodegradation rate of a-PHB-b-PPVL copolymers increases (PVL9 ≪ PVL17 < PVL23) along with the increase of crystalline PPVL domains. The biodegradation rate of PVL23 is similar to that of natural (crystalline) PHB. On the basis of a comparison of a-PHB-b-PPVL composition changes (by 1H NMR) with weight loss during biodegradation experiments, it is concluded that in the copolymers studied only the a-PHB block is attacked by the enzyme and that the crystalline block of nonbiodegradable PPVL efficiently promotes enzymatic attack to a-PHB, by providing a binding support to the enzyme.

Enzymatic Hydrolysis of Thioester Linkages in Bacterial Poly(3-hydroxybutyrate-co-3-mercaptopropionate)s by Poly(3-hydroxybutyrate) Depolymerase Isolated from Ralstonia pickettii T1

“…With further increasing the 3MP unit content, however, another crucial process, i.e., adsorption of enzyme on the surface of polyesters, should be taken into consideration, with noting only crystalline phase can provide a binding support to the enzyme. 23,24 It is expected that the amount of the enzyme adsorbed on subtract surface will decrease with the crystallinity. Crystallnity / %…”

Enzymatic biodegradation of chemosynthetic atactic P(3HB) enhanced by an amorphous non-biodegradable polymer: blend of atactic P(3HB) with PMMA

“…Scandola et al reported that a-P(3HB) was biodegraded in binary blends with natural poly(3-hydroxybutyrate-co-3hydroxyvalerate) (P(3HB-3HV), [14] poly-(e-caprolactone) (PCL) and poly(l-lactic acid) (PLLA), [15] and in di-block copolymer with poly(pivalolactone) (PPVL). [16] It is noteworthy that PCL, PLLA and PPVL are not degraded by the P((R)-3HB) depolymerases, but they are biodegradable polymers such as P((R)-3HB) and P(3HB-3HV). The phenomenon that a-P(3HB) segments are not biodegraded alone but biodegraded in the blends or in the diblock copolymer by the P((R)-3HB) depolymerase is very interesting and is called as crystalline-induced biodegradation.…”

“…The phenomenon that a-P(3HB) segments are not biodegraded alone but biodegraded in the blends or in the diblock copolymer by the P((R)-3HB) depolymerase is very interesting and is called as crystalline-induced biodegradation. [16] Analyses of the structural genes of the P((R)-3HB) depolymerases have revealed that these enzymes are organized with two domains and a linker region. [10,17,18] One of the two domains, the substrate binding domain, plays a role in binding to the P((R)-3HB) surface.…”

“…[13] Scandola et al further confirmed that the presence of crystalline poly-(hydroxyalkanoic acid) was a general requirement for the enzymatic hydrolysis of a-P(3HB) either in a binary blend or in a di-block copolymer. [16] Thus it seems interesting to elucidate the question whether the polymer, which is neither a crystalline polymer nor a biodegradable polyester, can provide the stable binding sites for the P((R)-3HB) depolymerase and can induce the biodegradation of a-P(3HB).…”

Thermal, Crystallization, and Biodegradation Behavior of Poly(3-hydroxybutyrate) Blends with Poly(butylene succinate-co-butylene adipate) and Poly(butylene succinate-co-ε-caprolactone)

“…Similar induced biodegradation has been also observed for chemosynthetic [(R,S)-{3-butyrolactone]-b-pivalolactone copolymers. 38 The similar case may also occur in the AB and CB blends.…”