Direct Observation of Enzymatic Degradation Behavior of Poly[(R)-3-hydroxybutyrate] Lamellar Single Crystals by Atomic Force Microscopy

Abstract

The enzymatic degradation behavior of solution-grown single crystals of poly[(R)-3hydroxybutyrate] (P(3HB)), which were adsorbed on the surface of highly ordered pyrolytic graphite, with an extracellular PHB depolymerase from Alcaligenes faecalis T1 was directly observed by atomic force microscopy. At the initial stage of degradation, enzymatic action of both adsorption and hydrolysis produced smaller crystal blocks by predominant degradation of distorted regions of a single crystal. Subsequently, the hydrolysis progressed from a generated end of the crystal block, resulting in the formation of cracks. The degradation also took place at a middle part of the crystal, yielding slits. Several cracks and slits stood in a line along the long axis of crystal, and further enzymatic hydrolysis combined the cracks and the slits into longer cracks. With these processes, the enzymatic degradation converted a lath-shaped lamellar single crystal into lathlike fingers and crystal fragments. It has been proposed from the degradation texture of one lamellar single crystal that inherent straight degradation pathways exist parallel to the average folding direction of the single crystal of P(3HB). The straight degradation pathway may be a mismatched region of molecular packing of adjacent polymer chains in a lamellar single crystal and may be generated with a crystal growth process as a history line.

Atomic Force Microscopy Investigation of Poly[(R)-3-hydroxybutyrate] Lamellar Single Crystals: Relationship between Molecular Weight and Enzymatic Degradation Behavior

“…[19] The degradation pathway can be explained by a loosely chain packing region along the long axis of crystal, that is, a linear switchboard region with a random reentry fold.…”

Degradation of Natural and Artificial Poly[(R)-3-hydroxyalkanoate]s: From Biodegradation to Hydrolysis

“…Enzymatic degradation of PHB single crystals with PHB depolymerases from Pseudomonas lemoignei (Nobes et al 1996) and R. pickettii T1 (Iwata et al 1997b;Murase et al 2001a) was observed with the transmission electron microscope and the atomic force microscope. These studies demonstrated that enzymatic hydrolysis progresses from the short ends of the lath-like-shaped PHB lamellar single crystals to form cracks along the long axis.…”

Real-time enzymatic degradation study of poly[(R)-3-hydroxybutyric acid] copolymer thin film by atomic force microscopy in buffer solution

“…Accordingly, the slit was generated by the degradation of less-ordered region in the lamellar crystal along the crystallographic a-axis. [19,20] As the degradation proceeded, the lamellar crystal revealed a splintered morphology at the tip of lamellar crystal (at area (f) in Figure 3G). After that, the splintered lamellar crystal was degraded and disappeared (at area (g) in Figure 3H).…”

“…[1][2][3][4][5] PHA materials can be hydrolyzed by specific microbial enzymes of extracellular poly(hydroxybutyrate) (PHB) depolymerases of microorganisms isolated from various environments. [6][7][8][9][10] To elucidate the mechanism of enzymatic hydrolysis of PHA materials with a PHB depolymerase, the enzymatic reaction has been investigated using single crystals [11][12][13][14][15][16][17][18][19][20] and films. [21][22][23][24][25][26][27][28][29][30][31] These reported results have indicated that the rates of enzymatic erosion for PHA materials are affected by both the chemical structure of monomeric units and the solid-state structure of samples.…”