Review Degradation of microbial polyesters

Abstract

Microbial polyhydroxyalkanoates (PHAs), one of the largest groups of thermoplastic polyesters are receiving much attention as biodegradable substitutes for non-degradable plastics. Poly(D-3-hydroxybutyrate) (PHB) is the most ubiquitous and most intensively studied PHA. Microorganisms degrading these polyesters are widely distributed in various environments. Although various PHB-degrading microorganisms and PHB depolymerases have been studied and characterized, there are still many groups of microorganisms and enzymes with varying properties awaiting various applications. Distributions of PHB-degrading microorganisms, factors affecting the biodegradability of PHB, and microbial and enzymatic degradation of PHB are discussed in this review. We also propose an application of a new isolated, thermophilic PHB-degrading microorganism, Streptomyces strain MG, for producing pure monomers of PHA and useful chemicals, including D-3-hydroxycarboxylic acids such as D-3-hydroxybutyric acid, by enzymatic degradation of PHB.

Degradable Polyhydroxyalkanoates as Herbicide Carriers

“…the degree of crystallinity, of the polymer. There are published data suggesting that depolymerizing enzymes preferentially attack amorphous regions of polymers rather than their ordered phases [8,30,31]. Assuming these observations are accurate, as the polymer is degraded and its amorphous phase is more rapidly disintegrated, the polymer that remains must exhibit an increase in its degree of crystallinity.…”

Fabrication and Degradation of Electrospun Polyhydroxyalkanoate Film

“…Another reason that supports the theory that the lipase enzyme may share a similar mechanism in substrate hydrolysis with PHA depolymerase is that lipase also have a common amino acid sequence around the active side, Gly-X 1 -Ser-X 2 -Gly, which is also observed in PHA depolymerase. The only difference is that the X 1 residue in PHA depolymerase is substituted with histidine in lipase (Tokiwa & Calabia, 2004). In this study, lipase from SigmaAldrich, extracted from porcine pancreas was used in the form of lyophilized powder with an activity of ≥20,000 units/mg protein.…”

Isolation and characterisation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) degrading actinomycetes and purification of PHBV depolymerase from newly isolatedStreptoverticillium kashmirense AF1

“…Most of the PHBV degrading microorganisms grow better at either ambient or mesophilic temperatures, whereas, only a few species like Bacillus strain TT96 (Tansengco and Tokiwa, 1998) and Streptomyces strain MG (Tokiwa and Calabia, 2004) were reported to degrade it at higher temperatures. There is little information on microbial degradation of PHBV at high temperatures (Takeda et al, 1998).…”