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The microbial degradation behavior of poly(3-hydroxybutyrate- co -3-hydroxyhexanoate) (PHBHHx) and its compound with several polyesters such as poly(butylene adipate- co -telephtharate) (PBAT), poly(butylene succinate) (PBS), and polylactic acid (PLA) in seawater was tested by a biological oxygen demand (BOD) method. PHBHHx showed excellent biodegradation in seawater in this study. In addition, the biodegradation rate of several blends was much influenced by the weight ratio of PHBHHx in their blends and decreased in accordance with the decrement of PHBHHX ratio. The surface morphology of the sheet was important factor for controlling the biodegradation rate of PHBHHx-containing blends in seawater., Competing Interests: The authors declare no conflict of interest.

In order to utilize biodegradable polymers as a functional material, it is important to make the best use of their biodegradability. Biodegradation of aliphatic polyesters, such as PCL, PBSA and P3HB, in seawater was investigated. BOD test using seawater and field test were carried out. As for BOD test, several factors were investigated such as tide, preservation of seawater, sampling place, population of microorganism, and seawater temperature. Biosynthesized P3HB and PHBHH showed rapid biodegradation by BOD method. As for synthetic polyesters, PCL also degraded fast. However, PBSA which is a popular biodegradable polymer in soil was not always biodegraded by BOD method with seawater. PBS and PBAT showed much slow biodegradation. Solvent cast films were immersed in the sea at a depth of 1.5 m. After 4 weeks, the weight loss of P3HB film was about 90%. On the contrary, the biodegradation by BOD method for 4 weeks was around 50%. Synthetic polyesters also showed obvious weight loss in field test, in contrast to the BOD results. • Marine biodegradation of various polyesters were examined by BOD method and Field test. • Some synthetic polymers did not show obvious biodegradation by BOD test in spite that they were biodegraded well in the sea. • BOD test is a useful method to examine factors effected on biodegradation. [ABSTRACT FROM AUTHOR]

Poly(ester amide)s are attracting attention because they potentially have excellent thermal and mechanical properties as well as biodegradability. In this study, we synthesized a series of novel poly(ester amide)s by introducing γ-aminobutyric acid (GABA) regularly into polyesters, and investigated their properties and biodegradabilities. GABA is the monomer unit of biodegradable polyamide 4 (PA4). The new poly(ester amide)s were synthesized from the reaction of ammonium tosylate derivatives of alkylene bis(γ-aminobutylate) and p-nitrophenyl esters of dicarboxylic acids. All the obtained polymers showed relatively high melting temperatures (Tm). Their thermal decomposition temperatures were improved in comparison with that of PA4 and higher enough than their Tm. The poly(ester amide)s exhibited higher biodegradability in seawater than the corresponding homopolyesters. Their biodegradabilities in activated sludge were also studied. [ABSTRACT FROM AUTHOR]

Herein, we report on the aquatic degradation of polyamide (nylon) 4. Polyamide 4 (PA4) has previously been shown to degrade in natural environments such as activated sludge and soil, as well as in vivo (when subcutaneously implanted in the backs of rats). In laboratory biodegradation tests of PA4, polyhydroxybutyrate (PHB), and polycaprolactone (PCL) in sampled seawater, the amount of oxygen absorption increased over time. PA4 degraded by about 30% in 4 weeks, which is comparable to that of PCL (30%) but less than that of PHB (60%). PA4 films were immersed in the sea and recovered at adequate intervals and weighed. The weight of the films decreased by 10–70% in 6 weeks, showing that PA4 is degraded in actual aquatic (sea) environments. We isolated PA4-degrading bacteria, strain MND-1, from the seawater used in the laboratory degradation tests. MND-1 is thought to belong to the family Alteromonadaceae from the DNA sequence of 16S rDNA. Gamma-aminobutyric acid (GABA) and GABA oligomers were detected in the PA4 degradation products. This indicates that the strain MND-1 hydrolyzes the amide bonds of PA4 into GABA oligomers and GABA. • We investigated the degradability of PA4 in seawater and in the sea. • PA4 was degraded in various seawaters in laboratory tests. • The weight of PA4 samples decreased in field degradation tests. Hence it was clarified that PA4 is degraded in the sea. • PA4-degrading bacteria MND-1 was purified and identified from seawater. • PResults of the degradation products analysis suggested that the isolated degrading bacteria degrades PA4 by hydrolysis. [ABSTRACT FROM AUTHOR]

The rising quantity of non-degradable microplastics in the world's oceans is becoming a major environmental and health issue. In this context, the advent of biodegradable plastics is a key step. However, information about the degradation of these polymers in the marine environment is scarce. In this study, the effect of particle size on laboratory-scale non-enzymatic hydrolysis, enzymatic hydrolysis, and seawater biodegradation of polymers was investigated. Compostable and biodegradable polymers, such as poly(l -lactic acid) (PLA) and poly(ε-caprolactone) (PCL), were cryo-milled and segregated into different size fractions. While non-enzymatic hydrolysis remained largely unaffected by the particle size, the enzymatic hydrolysis rate tended to increase with decreasing particle size for both polymers. The results indicated that the enzymatic hydrolysis rate could be accelerated by making the polymer particles finer. Furthermore, the seawater biodegradation rate and logarithm of the specific surface area were positively correlated. Therefore, it was expected that seawater biodegradation could also be accelerated. The hydrolysis rate of PLA in seawater, however, was not accelerated even with the smallest particle size, suggesting that the specific surface area, as well as the number of bacteria and concentration of extracellular enzymes on the particle surface, are essential for its seawater biodegradation. • Poly(l -lactic acid) and poly(ε-caprolactone) milled into various size fractions. • Powdered fractions subjected to hydrolysis and sea water biodegradation. • No effect of particle size on non-enzymatic hydrolysis of either polymer. • Enzymatic hydrolysis rate accelerated with smaller particle size. • Seawater biodegradation rate in finer poly(ε-caprolactone) powder also accelerated. [ABSTRACT FROM AUTHOR]

• Poly(L-lactide)- b -poly(2-methyl-1,3-propanediyl adipate)- b -poly(L-Lactide) (PLLA- b -PMPS- b -PLLAs) were synthesized as new biodegradable thermoplastic elastomers. • The triblock copolymers showed T g at lower than −40 °C and T m at around 150 °C. • Their tensile tests demonstrated their low modulus and high elongation. • The triblock copolymers and PMPA were found to be highly biodegradable in seawater. As a promising biodegradable and biorenewable alternative to ubiquitous petrochemical plastics, poly(L-lactide) (PLLA) can be widely employed in biomedical and pharmaceutical fields. In this work, triblock copolymers, poly(L-lactide)- b -poly(2-methyl-1,3-propanediyl adipate)- b -poly(L-lactide) (PLLA- b -PMPA- b -PLLA)s, were synthesized by two-step polymerization from 2-methyl-1,3-propanediol (MP), adipic acid (AA) and L-lactide (LLA) as new biodegradable thermoplastic elastomers. The copolymers exhibited glass-transition temperature at below −40 °C and melting temperature at 140–160 °C. These copolymers showed much higher elongation at break and lower tensile modulus than those of PLLA. Enzymatic degradation tests of the obtained copolymers were performed using proteinase K and lipase PS as catalysts in hydrolysis reaction to demonstrate rapid degradation for these copolymers. Seawater biodegradability test was conducted for 28 days for each sample. The triblock copolymer and PMPA homopolymer were found to show about 50% biodegradation within 28 days representing very high biodegradable property in seawater. [ABSTRACT FROM AUTHOR]