Reconfiguring Plant Metabolism for Biodegradable Plastic Production

Engineering of fast-growing Vibrio natriegens for biosynthesis of poly(3-hydroxybutyrate-co-lactate)

Poly(3-hydroxybutyrate-co-lactate) [P(3HB-co-LA)] is a highly promising valuable biodegradable material with good biocompatibility and degradability. Vibrio natriegens, owing to its fast-growth, wide substrate spectrum characteristics, was selected to produce P(3HB-co-LA). Herein, the crucial role of acetyltransferase PN96-18060 for PHB synthesis in V. natriegens was identified. Heterologous pathway of P(3HB-co-LA) was introduced into V. natriegens successfully, in addition, overexpression of the dldh gene led to 1.84 fold enhancement of the lactate content in P(3HB-co-LA). Finally, the production of P(3HB-co-LA) was characterized under different carbon sources. The lactate fraction in P(3HB-co-LA) was increased to 28.3 mol% by the modification, about 1.84 times of that of the control. This is the first successful case of producing the P(3HB-co-LA) in V. natriegens. Collectively, this study showed that V. natriegens is an attractive host organism for producing P(3HB-co-LA) and has great potential to produce other co-polymers.

Commercialization potential of agro-based polyhydroxyalkanoates biorefinery: A technical perspective on advances and critical barriers

The exponential increase in the use and careless discard of synthetic plastics has created an alarming concern over the environmental health due to the detrimental effects of petroleum based synthetic polymeric compounds. Piling up of these plastic commodities on various ecological niches and entry of their fragmented parts into soil and water has clearly affected the quality of these ecosystems in the past few decades. Among the many constructive strategies developed to tackle this global issue, use of biopolymers like polyhydroxyalkanoates as sustainable alternatives for synthetic plastics has gained momentum. Despite their excellent material properties and significant biodegradability, polyhydroxyalkanoates still fails to compete with their synthetic counterparts majorly due to the high cost associated with their production and purification thereby limiting their commercialization. Usage of renewable feedstocks as substrates for polyhydroxyalkanoates production has been the thrust area of research to attain the sustainability tag. This review work attempts to provide insights about the recent developments in the production of polyhydroxyalkanoates using renewable feedstock along with various pretreatment methods used for substrate preparation for polyhydroxyalkanoates production. Further, the application of blends based on polyhydroxyalkanoates, and the challenges associated with the waste valorization based polyhydroxyalkanoates production strategy is elaborated in this review work.

Trends in PHA Production by Microbially Diverse and Functionally Distinct Communities

Along with the wide applications of conventional plastics, they have a large number of disadvantages like their non-biodegradable nature, dependency on fossil fuels and the release of large amounts of toxic materials in the environment. Therefore, to resolve these problems, a number of bioplastics are studied, out of which polyhydroxyalkanoates are considered as the best alternatives. Polyhydroxyalkanoates (PHAs) are produced by microorganisms as intracellular granules during stressful conditions. Though a wide range of organisms can naturally produce PHAs, only a few of them can be used for commercial production. Therefore, more diverse organisms that accumulate a considerable amount of PHAs and also reduce the production cost need to be exploited. Transgenic plants, recombinant bacteria, algae and extremophiles are some diverse organisms that produce a high amount of PHAs at a low cost. So, if potential organisms are used for PHA production, bioplastics will be able to completely replace petroleum-based polymers. Therefore, our review mainly focuses on production of PHAs using potential organisms so that amount of PHAs produced is high and cost-effective which would further help in the commercialization of PHAs.

Recent developments in short- and medium-chain- length Polyhydroxyalkanoates: Production, properties, and applications

Developing renewable resource-based plastics with complete biodegradability and a minimal carbon footprint can open new opportunities to effectively manage the end-of-life plastics waste and achieve a low carbon society. Polyhydroxyalkanoates (PHAs) are biobased and biodegradable thermoplastic polyesters that accumulate in microorganisms (e.g., bacterial, microalgal, and fungal species) as insoluble and inert intracellular inclusion. The PHAs recovery from microorganisms, which typically involves cell lysis, extraction, and purification, provides high molecular weight and purified polyesters that can be compounded and processed using conventional plastics converting equipment. The physio-chemical, thermal, and mechanical properties of the PHAs are comparable to traditional synthetic polymers such as polypropylene and polyethylene. As a result, it has attracted substantial applications interest in packaging, personal care, coatings, agricultural and biomedical uses. However, PHAs have certain performance limitations (e.g. slow crystallization), and substantially more expensive than many other polymers. As such, more research and development is required to enable them for extensive use. This review provides a critical review of the recent progress achieved in PHAs production using different microorganisms, downstream processing, material properties, processing avenues, recycling, aerobic and anaerobic biodegradation, and applications.

Recombinant production of poly-(3-hydroxybutyrate) by Bacillus megaterium utilizing millet bran and rapeseed meal hydrolysates

Fermentative poly-3-hydroxybutyrate (PHB) production is mainly limited by the cost of raw material. In this present study, low-cost feedstock viz., millet bran residue (MBRH) and rapeseed meal hydrolysates were successfully utilized for PHB production. Metabolic engineering of Bacillus megaterium by co-expression of both precursor (phbRBC) and NADPH cofactor regeneration (zwf) genes resulted in 2.67-fold enhancement in PHB accumulation compared to wild strain. Modified logistic model characterized B.megaterium growth and PHB production effectively. The kinetic analysis proved that maximum cell concentration (15.01 g.L^-1) and growth-associated constant (0.22 g.g^-1) were found to be higher for initial MBRH concentration (S₀ = 20 g.L^-1). PHB production kinetics elucidated its expression in B.megaterium was growth-associated. PHB synthesized by B.megaterium was characterized using FTIR, NMR, XRD, DSC/TGA, FESEM and the physio-chemical properties enumerated its as a potential biodegradable plastic for industrial application.

Plant Biosystems Design Research Roadmap 1.0

Human life intimately depends on plants for food, biomaterials, health, energy, and a sustainable environment. Various plants have been genetically improved mostly through breeding, along with limited modification via genetic engineering, yet they are still not able to meet the ever-increasing needs, in terms of both quantity and quality, resulting from the rapid increase in world population and expected standards of living. A step change that may address these challenges would be to expand the potential of plants using biosystems design approaches. This represents a shift in plant science research from relatively simple trial-and-error approaches to innovative strategies based on predictive models of biological systems. Plant biosystems design seeks to accelerate plant genetic improvement using genome editing and genetic circuit engineering or create novel plant systems through de novo synthesis of plant genomes. From this perspective, we present a comprehensive roadmap of plant biosystems design covering theories, principles, and technical methods, along with potential applications in basic and applied plant biology research. We highlight current challenges, future opportunities, and research priorities, along with a framework for international collaboration, towards rapid advancement of this emerging interdisciplinary area of research. Finally, we discuss the importance of social responsibility in utilizing plant biosystems design and suggest strategies for improving public perception, trust, and acceptance.