Biodegradability of poly(3-hydroxyalkanoate) and poly(ε-caprolactone) via biological carbon cycles in marine environments

Abstract

Approximately 4.8–12.7 million tons of plastic waste has been estimated to be discharged into marine environments annually by wind and river currents. The Ellen MacArthur Foundation warns that the total weight of plastic waste in the oceans will exceed the total weight of fish in 2050 if the environmental runoff of plastic continues at the current rate. Hence, biodegradable plastics are attracting attention as a solution to the problems caused by plastic waste. Among biodegradable plastics, polyhydroxyalkanoates (PHAs) and poly(ε-caprolactone) (PCL) are particularly noteworthy because of their excellent marine biodegradability. In this review, the biosynthesis of PHA and cutin, a natural analog of PCL, and the biodegradation of PHA and PCL in carbon cycles in marine ecosystems are discussed. PHA is biosynthesized and biodegraded by various marine microbes in a wide range of marine environments, including coastal, shallow-water, and deep-sea environments. Marine cutin is biosynthesized by marine plants or obtained from terrestrial environments, and PCL and cutin are biodegraded by cutin hydrolytic enzyme-producing microbes in broad marine environments. Thus, biological carbon cycles for PHA and PCL exist in the marine environment, which would allow materials made of PHA and PCL to be quickly mineralized in marine environments.

Biodegradation of Hemicellulose-Cellulose-Starch-Based Bioplastics and Microbial Polyesters

“…However, factors that influence the degradation of composites and bioplastics are necessary. Some of the marine microorganisms that are known to degrade PHAs [94] As in polysaccharide-based bioplastics, crystallinity in polyester bioplastics from microbial synthesis plays an important role in the biodegradation process. In bioplastics with higher proportions of amorphous regions, depolymerization occurs more quickly through abiotic or biotic action.…”

Improvement of Paper Resistance against Moisture and Oil by Coating with Poly(-3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and Polycaprolactone (PCL)

“…For example, strips of PHBV with a thickness of 1 mm showed a total mass loss of 100% after 70 days at 20-24 • C in industrial composting facilities; a complete degradation via composting can be observed for PCL within a few weeks. Figures on biodegradation of PHA and PHB can be found in another review [13] and the biodegradability in marine environment of PHA and PCL has been extensively discussed [14].…”

Poly-β-Hydroxybutyrate Production by Rhodopseudomonas sp. Grown in Semi-Continuous Mode in a 4 L Photobioreactor

“…Depolymerases catalyze hydrolysis, thus producing free D(−)-3-hydroxybutyrate, which is then oxidized to acetoacetate by a NAD-specific dehydrogenase. Degradation of PHA can be realized in various environments such as soil, fresh water, and marine environments [37,38]. Some of the most dominant PHA-degrading microorganisms belong to the bacterial genera of Bacillus, Ralstonia, Pseudomonas, Alcaligenes, Mycobacterium, Comamonas, Acinetobacter, Azospirillum, and Streptomyces [37,39,40].…”