Biological Synthesis of Polymers

Triglycerides have not only been used as feedstocks for chemical production of bioplastics, but also the enzymatic production of polymers. Polyhydroxyalkanoates were produced by using Bras Sica carrinata oil with high erucic acid content (35-48%) as a feedstock iox Pseudomonas 

The perception of generating naturally sourced plastic materials may be that of an academic curiosity but there are many industrial applications that have been investigated. The readily available, low-cost feedstock is attractive to companies looking to get a competitive edge over their rivals. The inherent varied reactivity allows manipulations to be carried out efficiently to optimize the properties of the desired application. 

One of the main issues with the use of plant oils has been the inferior physical properties of the polymers that they are used to make. This is largely due to the fact that they have been bred and optimized for food usage over the past several hundred years and are not fit for purpose. 

The combination with fibres has proved difficult however. Often there are issues with compatibility between bio-resins and fibres (both natural and synthetic), which cause defects in the composite structure and ultimately poorer physical properties. Castor-oil polyurethane was compared with phenolic resins when infused over sisal fibres however, the phenolic resins showed better structural performance when compared with the castor oil-based material [52]. This is not always the case, as some improvements have been made. Soybean oil thermoset polymers were used in a glass/flax hybrid composite resulting in improved mechanical performance [73], Thermoset resins were produced from triglyceride oils with a wide range of properties (tensile modulus 1-2 GPa, glass transition temperature Tg 70-120 °C) and glass- and hemp- fibre composites were manufactured [74,75]. 

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While biological synthesis of polymers confers many advantages, it also imposes some limitations. As described previously, there are several issues that must be considered when designing the monomer and concatamer gene sequences. Furthermore, the potential toxicity of the genetically engineered polymer to the expression host, and the resultant effect on the integrity of the product must be considered. 

A. Mouflou, J. G. Zilliox, G. Beinert, Ph. Chaumont, and J. Herz, in Biological Synthesis of Polymer Networks (O. Kramer, ed.), Elsevier Applied Science, London, 1988, pp. 483-493. 

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