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Blends of Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate) with Fruit Pulp Biowaste Derived Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate-co-3-Hydroxyhexanoate) for Organic Recycling Food Packaging.

ABSTRACT: In the present study, a new poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) [P(3HB-co-3HV-co-3HHx)] terpolyester with approximately 68 mol% of 3-hydroxybutyrate (3HB), 17 mol% of 3-hydroxyvalerate (3HV), and 15 mol% of 3-hydroxyhexanoate (3HHx) was obtained via the mixed microbial culture (MMC) technology using fruit pulps as feedstock, a processing by-product of the juice industry. After extraction and purification performed in a single step, the P(3HB-co-3HV-co-3HHx) powder was melt-mixed, for the first time, in contents of 10, 25, and 50 wt% with commercial poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). Thereafter, the resultant doughs were thermo-compressed to obtain highly miscible films with good optical properties, which can be of interest in rigid and semirigid organic recyclable food packaging applications. The results showed that the developed blends exhibited a progressively lower melting enthalpy with increasing the incorporation of P(3HB-co-3HV-co-3HHx), but retained the PHB crystalline morphology, albeit with an inferred lower crystalline density. Moreover, all the melt-mixed blends were thermally stable up to nearly 240 °C. As the content of terpolymer increased in the blends, the mechanical response of their films showed a brittle-to-ductile transition. On the other hand, the permeabilities to water vapor, oxygen, and, more notably, limonene were seen to increase. On the overall, this study demonstrates the value of using industrial biowaste derived P(3HB-co-3HV-co-3HHx) terpolyesters as potentially cost-effective and sustainable plasticizing additives to balance the physical properties of organic recyclable polyhydroxyalkanoate (PHA)-based food packaging materials.

SUBMITTER: Melendez-Rodriguez B

PROVIDER: S-EPMC8038484 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Poly(hydroxybutyrate-co-hydroxyhexanoate) [P(HB-co-HHx)] and poly(hydroxybutyrate-co-hydroxyvalerate-co-hydroxyhexanoate) [P(HB-co-HV-co-HHx)] demonstrate interesting mechanical and thermal properties as well as excellent biocompatibility, making them suitable for multiple applications and notably biomedical purposes. The production of such polymers was described in Rhodospirillum rubrum, a purple nonsulfur bacteria in a nutrient-lacking environment where the HHx synthesis is triggered by the presence of hexanoate in the medium. However, the production of P(HB-co-HHx) under nutrient-balanced growth conditions in R. rubrum has not been described so far, and the assimilation of hexanoate is poorly documented. In this study, we used proteomic analysis and a mutant fitness assay to demonstrate that hexanoate assimilation involve β-oxidation and the ethylmalonyl-coenzyme A (CoA) (EMC) and methylbutanoyl-CoA (MBC) pathways, both being anaplerotic pathways already described in R. rubrum. Polyhydroxyalkanoate (PHA) production is likely to involve the de novo fatty acid synthesis pathway. Concerning the polymer composition, HB is the main component of the polymer, probably as acetyl-CoA and butyryl-CoA are intermediates of hexanoate assimilation pathways. When no essential nutrient is lacking in the medium, the synthesis of PHA seems to help maintain the redox balance of the cell. In this framework, we showed that the fixation of CO2 is required to sustain the growth. An increase in the proportion of HHx in the polymer was observed when redox stress was engendered in the cell under bicarbonate-limiting growth conditions. The addition of isoleucine or valerate in the medium also increased the HHx content of the polymer and allowed the production of a terpolymer of P(HB-co-HV-co-HHx). IMPORTANCE The use of purple bacteria, which can assimilate volatile fatty acids, for biotechnological applications has increased, since they reduce the production costs of added-value compounds such as PHA. P(HB-co-HHx) and P(HB-co-HV-co-HHx) have demonstrated interesting properties, notably for biomedical applications. In a nutrient-lacking environment, R. rubrum is known to synthesize such polymers when hexanoate is used as the carbon source. However, their production in R. rubrum in non-nutrient-lacking growth conditions has not been described so far, and the assimilation of hexanoate is poorly documented. As the carbon source and its assimilation directly impact the polymer composition, we studied under non-nutrient-lacking growth conditions the assimilation pathway of hexanoate and PHA production in R. rubrum. Proteomic analysis and mutant fitness assays allowed us to explain PHA production and composition. An increase in HHx content of the polymer and production of P(HB-co-HV-co-HHx) was possible using the knowledge gained on metabolism under hexanoate growth conditions.

Project description:Cell-based therapies are major focus of current research for treatment of liver diseases. In this study, mesenchymal stem cells were isolated from human umbilical cord Wharton's jelly (WJ-MSCs). Results confirmed that WJ-MSCs isolated in this study could express the typical MSC-specific markers and be induced to differentiate into adipocytes, osteoblasts, and chondrocytes. They could also be induced to differentiate into hepatocyte-like cells. Poly (3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate) (PHBVHHx) is a new member of polyhydroxyalkanoate family and biodegradable polyester produced by bacteria. PHBVHHx scaffolds showed much higher cell attachment and viability than the other polymers tested. PHBVHHx scaffolds loaded with WJ-MSCs were transplanted into liver-injured mice. Liver morphology improved after 30 days of transplantation and looked similar to normal liver. Concentrations of serum alanine aminotransferase and total bilirubin were significantly lower, and albumin was significantly higher on days 14 and 30 in the WJ-MSCs+scaffold group than in the carbon tetrachloride (CCl4) group. Hematoxylin-eosin staining showed that liver had similar structure of normal liver lobules and similar size and shape of normal hepatic cells, and Masson staining demonstrated that liver had less blue staining for collagen after 30 days of transplantation. Real-time reverse transcription-polymerase chain reaction (RT-PCR) showed that the expression of the bile duct epithelial cell gene CK-19 in mouse liver is significantly lower on days 14 and 30 in the WJ-MSCs+scaffold group than in the CCl4 group. Real-time RT-PCR, immunocytochemistry, and periodic acid-Schiff staining showed that WJ-MSCs in scaffolds differentiated into hepatocyte-like cells on days 14 and 30 in the WJ-MSCs+scaffold group. Real-time RT-PCR also demonstrated that WJ-MSCs in scaffolds expressed endothelial cell genes Flk-1, vWF, and VE-cadherin on days 14 and 30 in the WJ-MSCs+scaffold group, indicating that WJ-MSCs also differentiated into endothelial-like cells. These results demonstrated that PHBVHHx scaffolds loaded with WJ-MSCs significantly promoted the recovery of injured liver and could be further studied for liver tissue engineering.

Dataset Information

Blends of Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate) with Fruit Pulp Biowaste Derived Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate-co-3-Hydroxyhexanoate) for Organic Recycling Food Packaging.

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