Modern synthetic methods have revolutionized polymer chemistry through the development of new and powerful strategies for the controlled synthesis of complex polymer architectures. 1-5 Many of these developments were spawned by new classes of transition metal catalysts for the synthesis of new polyolefin microstructures, 5 the design of highly efficient families of “living” polymerization strategies for the synthesis of block, graft, and star polymers, 6-12 controlled methods for the synthesis of dendritic macromolecules, 3,13,14

Organocatalytic ring-opening polymerization.

The growing ecological and environmental consciousness has driven efforts for development of new innovative materials for various end-use applications. Polymers synthesized from natural resources, have gained considerable research interest in the recent years. This review paper is intended to provide a brief outline of work that covers in the area of biocomposites, major class of biodegradable polymers, natural fibres, as well as their manufacturing techniques and properties has been highlighted. Various surface modification methods were incorporated to improve the fibre–matrix adhesion resulting in the enhancement of mechanical properties of the biocomposites. Moreover, an economical impact and future direction of these materials has been critically reviewed. This review concludes that the biocomposites form one of the emerging areas in polymer science that gain attention for use in various applications ranging from automobile to the building industries.

A review of the recent developments in biocomposites based on natural fibres and their application perspectives

Various bacterial species accumulate intracellular polyhydroxyalkanoates (PHAs) granules as energy and carbon reserves inside their cells. PHAs are biodegradable, environmentally friendly and biocompatible thermoplastics. Varying in toughness and flexibility, depending on their formulation, they can be used in various ways similar to many nonbiodegradable petrochemical plastics currently in use. They can be used either in pure form or as additives to oil-derived plastics such as polyethylene. However, these bioplastics are currently far more expensive than petrochemically based plastics and are therefore used mostly in applications that conventional plastics cannot perform, such as medical applications. PHAs are immunologically inert and are only slowly degraded in human tissue, which means they can be used as devices inside the body. Recent research has focused on the use of alternative substrates, novel extraction methods, genetically enhanced species and mixed cultures with a view to make PHAs more commercially attractive.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2672.2007.03335.x

Bacterial synthesis of biodegradable polyhydroxyalkanoates

The chemomechanical properties of microbial polyhydroxyalkanoates

This chapter examines the physical and mechanical properties of biodegradable polymers derived from renewable sources and petrochemical sources with a focus on their applications Polymers from renewable sources include poly(lactic acid), polyhydroxyalkanoates (PHA), and thermoplastic starch (TPS) Polymers from petrochemical sources include aliphatic polyesters and copolyesters, aromatic polyesters and copolyesters, poly(caprolactone), poly(esteramide), and poly(vinyl alcohol) The physical properties, based on which biodegradable polymers are categorized, are their melt flow rate, density, and transparency Mechanical properties include their tensile strength at yield, elongation at yield, and tensile modulus There are many applications of compostable polymer materials in the commercialized or development/demonstration stage They are used in the packaging industry, in agriculture and horticulture, in short life consumer goods, and long life consumer goods The major markets of compostable polymer materials are agriculture, fisheries, civil engineering, constructions, food packaging, and many more The increased interest in compostable polymers is a response to the growing price of petroleum and growing consumer demand for sustainable products Improvement in processing technologies and the effect of scale-up has decreased the price of compostable polymers

Properties and applications

Recent advances in microbial polyhydroxyalkanoates

Statistical media optimization studies for growth and PHB production by Ralstonia eutropha

Economic production technology for a biodegradable polymer (poly-beta-hydroxybutyrate, PHB) is urgently required to replace conventional polymers, which have an inherent disadvantage of staying in the environment forever. Various approaches have been applied for improving the productivity and reducing the production cost, which are considered to be the two major problems associated with industrial production of PHB. One of the engineering approaches to improve PHB productivity could be to design and implement model-based fed-batch cultivations to provide desirable nutrient availability. In the present study, growth and intracellular biopolymer storage kinetics of Ralstonia eutropha was studied in a batch cultivation process. It featured 19.7 g/L biomass and 10.89 g/L PHB with a productivity of 0.18 g/L.h. The effect of carbon, nitrogen, and phosphate limitations and inhibitions on growth was studied in detail. A structured model featuring typical growth limitations and/or possible inhibitions was then proposed. The value of the model parameters was found by minimizing the difference between experimental value and model simulation at all data points and for all process variables. The optimal batch model parameter values obtained above were used to solve the differential equations numerically. The simulated data obtained in this way was then compared with the experimental data to establish the validity of the batch model. The proposed model was then compared with literature reported mathematical models to reconfirm its accuracy. Statistical validity of the developed model and historical models to describe the observed experimental kinetics was then investigated to reinforce the accuracy of the developed simple model.

Shilpi Khanna

Papers

Recent advances in microbial polyhydroxyalkanoates

Statistical media optimization studies for growth and PHB production by Ralstonia eutropha

A simple structured mathematical model for biopolymer (PHB) production.

Computer simulated fed-batch cultivation for over production of PHB: A comparison of simultaneous and alternate feeding of carbon and nitrogen

Optimization of nutrient feed concentration and addition time for production of poly(β-hydroxybutyrate)