June 2023
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5 Reads
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June 2023
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5 Reads
May 2023
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260 Reads
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7 Citations
Microorganisms
Biodegradable polymers offer a potential solution to marine pollution caused by plastic waste. The marine biofilms that formed on the surfaces of poly(lactide acid) (PLA) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) were studied. Bioplastics were exposed for 6 months to marine conditions in the Mediterranean Sea, and the biofilms that formed on their surfaces were assessed. The presence of specific PLA and PHBV degraders was also studied. PHBV showed extensive areas with microbial accumulations and this led to higher microbial surface densities than PLA (4.75 vs. 5.16 log CFU/cm2). Both polymers’ surfaces showed a wide variety of microbial structures, including bacteria, fungi, unicellular algae and choanoflagellates. A high bacterial diversity was observed, with differences between the two polymers, particularly at the phylum level, with over 70% of bacteria affiliated to three phyla. Differences in metagenome functions were also detected, revealing a higher presence of proteins involved in PHBV biodegradation in PHBV biofilms. Four bacterial isolates belonging to the Proteobacteria class were identified as PHBV degraders, demonstrating the presence of species involved in the biodegradation of this polymer in seawater. No PLA degraders were detected, confirming its low biodegradability in marine environments. This was a pilot study to establish a baseline for further studies aimed at comprehending the marine biodegradation of biopolymers.
May 2023
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139 Reads
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7 Citations
Polymers
Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) has gained attention as a possible substitute for conventional polymers that could be integrated into the organic recycling system. Biocomposites with 15% of pure cellulose (TC) and woodflour (WF) were prepared to analyze the role of lignin on their compostability (58 °C) by tracking the mass loss, CO2 evolution, and the microbial population. Realistic dimensions for typical plastic products (400 µm films), as well as their service performance (thermal stability, rheology), were taken into account in this hybrid study. WF showed lower adhesion with the polymer than TC and favored PHBV thermal degradation during processing, also affecting its rheological behavior. Although all materials disintegrated in 45 days and mineralized in less than 60 days, lignin from woodflour was found to slow down the bioassimilation of PHBV/WF by limiting the access of enzymes and water to easier degradable cellulose and polymer matrix. According to the highest and the lowest weight loss rates, TC incorporation allowed for higher mesophilic bacterial and fungal counts, while WF seemed to hinder fungal growth. At the initial steps, fungi and yeasts seem to be key factors in facilitating the later metabolization of the materials by bacteria.
November 2022
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123 Reads
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12 Citations
International Journal of Biological Macromolecules
Being aware of the global problem of plastic pollution, our society is claiming new bioplastics to replace conventional polymers. Balancing their mechanical performance is required to increase their presence in the market. Brittleness of bacterial poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was attempted to be decreased by melt blending with flexible starch-based poly(butylene succinate-co-butylene adipate) (PBSA). An epoxy-functionalized chain extender was used to enhance interaction between both immiscible biopolyesters. Mechanical performance, morphology, rheology, and crystallization behavior of injection-molded PHBV-PBSA blends (70–30, 50–50, and 30–70 wt%) were assessed in the presence and absence of the chain extender. Crystallization of PHBV was hindered, which was reflected in the improvement of mechanical properties. When PBSA >50 %, the homogeneity of results increased within the same sample while for PHBV-PBSA 70–30 wt% the elongation was 45 % higher. During the flexural test, it changed from brittle to non-breakable. The additive did not change the type of morphology developed by each blend nor the toughening mechanisms, so impact strength was barely affected. However, it reduced the size of dispersed phase domains due to a viscosity change, improving their processability. The higher the PHBV in the blend, the higher the effect of the chain extender.
June 2022
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171 Reads
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22 Citations
Polymers
Poly(3-hydroxybutyrate-co-3-valerate) (PHBV), being one of the most studied and commercially available polyhydroxyalkanoates (PHAs), presents an intrinsic brittleness and narrow processing window that currently hinders its use in several plastic applications. The aim of this study was to develop a biodegradable PHA-based blend by combining PHBV with poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), another copolyester of the PHA family that shows a more ductile behavior. Blends of PHBV with 20% wt., 30% wt., and 40% wt. of PHBH were obtained by melt mixing, processed by cast extrusion in the form of films, and characterized in terms of their morphology, crystallization behavior, thermal stability, mechanical properties, and thermoformability. Full miscibility of both biopolymers was observed in the amorphous phase due to the presence of a single delta peak, ranging from 4.5 °C to 13.7 °C. Moreover, the incorporation of PHBH hindered the crystallization process of PHBV by decreasing the spherulite growth rate from 1.0 µm/min to 0.3 µm/min. However, for the entire composition range studied, the high brittleness of the resulting materials remained since the presence of PHBH did not prevent the PHBV crystalline phase from governing the mechanical behavior of the blend. Interestingly, the addition of PHBH greatly improved the thermoformability by widening the processing window of PHBV by 7 s, as a result of the increase in the melt strength of the blends even for the lowest PHBH content.
May 2022
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57 Reads
In this contribution, two relevant aspects for massive industrial implementation of PHA materials will be tackled. First, the results of several studies assessing PHA-based plastic formulations performance in real environments will be presented and discussed. Second, the results on the study of the biodegradation of PHA will be analyzed, with special focus in real marine environment.
January 2022
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15 Reads
SSRN Electronic Journal
September 2021
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31 Reads
September 2021
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19 Reads
... Regarding bioplastics, despite their limited presence in natural environments, extensive research has identified microorganisms capable of biodegrading them. Examples include degraders of polyhydroxyalkanoates (PHAs), such as bacteria from the genera Pseudomonas, Bacillus, Ruegeria, and Vibrio (Boyandin et al. 2012;Marín et al. 2023), polybutylene adipate terephthalate (PBAT), such as the bacterial genera Marimonas and Thermobifida (Delacuvellerie et al. 2021;Jia et al. 2023), PLA, such as bacteria from the genera Actinomadura, Streptomyces, Pseudomonas, and a consortium bacteria from plastic waste (Sriyapai et al. 2018;Noor et al. 2020;Mistry et al. 2022) and polybutylene succinate-co-adipate (PBSA), such as members from the bacterial genera Actinomadura and Laceyella and from the fungus Aspergillus (Sriyapai et al. 2018;Chien et al. 2022). ...
May 2023
Microorganisms
... Within these communities, microorganisms engage in both cooperative and competitive interactions. Different microbial species contribute to different stages of the degradation process, and these interactions can impact the dynamics of biodegradation [96]. ...
May 2023
Polymers
... Above this temperature, a drastic drop in the storage modulus was observed for all samples. This fall in E' from ≈3300 MPa to <900 MPa was related to the transition from a glassy to a rubbery state, i.e., the glass transition temperature of PCL (α relaxation, T α ) [47]. Since this transition occurs in a broad temperature range, the tan δ (ratio of loss to storage moduli) peak criterion was used to determine the T g of the samples at the different frequencies, and the obtained values are reported in Table 3. ...
November 2022
International Journal of Biological Macromolecules
... Different studies of PHA biodegradation have been reported in compost and soil media (Arcos-Hernandez et al., 2012;Chan et al., 2019;David et al., 2019;Gonçalves et al., 2009;Lammi et al., 2019;Muniyasamy et al., 2016;Weng et al., 2010), while less attention has been devoted to biodegradation in marine environments (Briassoulis et al., 2019(Briassoulis et al., , 2020Deroiné et al., 2015;{Formatting Citation};Feijoo et al., 2022;Meereboer et al., 2021). However, biodegradation in marine ecosystems requires in-depth studies since the accumulation of plastics will occur in this environment. ...
June 2022
Polymers