Composite of medium-chain-length polyhydroxyalkanoates-co-methyl acrylate and carbon nanotubes as innovative electrodes modifier in microbial fuel cell

A Review of Current Achievements and Recent Challenges in Bacterial Medium-Chain-Length Polyhydroxyalkanoates: Production and Potential Applications

Using petroleum-derived plastics has contributed significantly to environmental issues, such as greenhouse gas emissions and the accumulation of plastic waste in ecosystems. Researchers have focused on developing ecofriendly polymers as alternatives to traditional plastics to address these concerns. This review provides a comprehensive overview of medium-chain-length polyhydroxyalkanoates (mcl-PHAs), biodegradable biopolymers produced by microorganisms that show promise in replacing conventional plastics. The review discusses the classification, properties, and potential substrates of less studied mcl-PHAs, highlighting their greater ductility and flexibility compared to poly(3-hydroxybutyrate), a well-known but brittle PHA. The authors summarize existing research to emphasize the potential applications of mcl-PHAs in biomedicine, packaging, biocomposites, water treatment, and energy. Future research should focus on improving production techniques, ensuring economic viability, and addressing challenges associated with industrial implementation. Investigating the biodegradability, stability, mechanical properties, durability, and cost-effectiveness of mcl-PHA-based products compared to petroleum-based counterparts is crucial. The future of mcl-PHAs looks promising, with continued research expected to optimize production techniques, enhance material properties, and expand applications. Interdisciplinary collaborations among microbiologists, engineers, chemists, and materials scientists will drive progress in this field. In conclusion, this review serves as a valuable resource to understand mcl-PHAs as sustainable alternatives to conventional plastics. However, further research is needed to optimize production methods, evaluate long-term ecological impacts, and assess the feasibility and viability in various industries.

Current advances and emerging trends in sustainable polyhydroxyalkanoate modification from organic waste streams for material applications

The current processes for producing polyhydroxyalkanoates (PHAs) are costly, owing to the high cost of cultivation feedstocks, and the need to sterilise the growth medium, which is energy-intensive. PHA has been identified as a promising biomaterial with a wide range of potential applications and its functionalization from waste streams has made significant advances recently, which can help foster the growth of a circular economy and waste reduction. Recent developments and novel approaches in the functionalization of PHAs derived from various waste streams offer opportunities for addressing these issues. This study focuses on the development of sustainable, efficient, and cutting-edge methods, such as advanced bioprocess engineering, novel catalysts, and advances in materials science. Chemical techniques, such as epoxidation, oxidation, and esterification, have been employed for PHA functionalization, while enzymatic and microbial methods have indicated promise. PHB/polylactic acid blends with cellulose fibers showed improved tensile strength by 24.45-32.08 % and decreased water vapor and oxygen transmission rates while PHB/Polycaprolactone blends with a 1:1 ratio demonstrated an elongation at break four to six times higher than pure PHB, without altering tensile strength or elastic modulus. Moreover, PHB films blended with both polyethylene glycol and esterified sodium alginate showed improvements in crystallinity and decreased hydrophobicity.

Artificial polyhydroxyalkanoate poly[2-hydroxybutyrate-block-3-hydroxybutyrate] elastomer-like material

The first polyhydroxyalkanoate (PHA) block copolymer poly(2-hydroxybutyrate-b-3-hydroxybutyrate) [P(2HB-b-3HB)] was previously synthesized using engineered Escherichia coli expressing a chimeric PHA synthase PhaCAR with monomer sequence-regulating capacity. In the present study, the physical properties of the block copolymer and its relevant random copolymer P(2HB-ran-3HB) were evaluated. Stress-strain tests on the P(88 mol% 2HB-b-3HB) film showed an increasing stress value during elongation up to 393%. In addition, the block copolymer film exhibited slow contraction behavior after elongation, indicating that P(2HB-b-3HB) is an elastomer-like material. In contrast, the P(92 mol% 2HB-ran-3HB) film, which was stretched up to 692% with nearly constant stress, was stretchable but not elastic. The differential scanning calorimetry and wide-angle X-ray diffraction analyses indicated that the P(2HB-b-3HB) contained the amorphous P(2HB) phase and the crystalline P(3HB) phase, whereas P(2HB-ran-3HB) was wholly amorphous. Therefore, the elasticity of P(2HB-b-3HB) can be attributed to the presence of the crystalline P(3HB) phase and a noncovalent crosslinked structure by the crystals. These results show the potential of block PHAs as elastic materials.