Second-generation functionalized mediumchain- length polyhydroxyalkanoates: the gateway to high-value bioplastic applications

Resum

Polyhydroxyalkanoates (PHAs) are biodegradable biocompatible polyesters, which accumulate as granulesin the cytoplasm of many bacteria under unbalanced growth conditions. Medium-chain-length PHAs (mcl-PHAs), characterizedby C6-C14 branched monomer chains and typically produced by Pseudomonas species, are promising thermoelastomers,as they can be further modified by introducing functional groups in the side chains. Functionalized PHAs areobtained either by feeding structurally related substrates processed through the β-oxidation pathway, or using specificstrains able to transform sugars or glycerol into unsaturated PHA by de novo fatty-acid biosynthesis. Functionalized mcl-PHAs provide modified mechanical and thermal properties, and consequently have new processing requirements andhighly diverse potential applications in emergent fields such as biomedicine. However, process development and sampleavailability are limited due to the toxicity of some precursors and still low productivity, which hinder investigation. Conversely,improved mutant strains designed through systems biology approaches and cofeeding with low-cost substratesmay contribute to the widespread application of these biopolymers. This review focuses on recent developments in theproduction of functionalized mcl-PHAs, placing particular emphasis on strain and bioprocess design for cost-effectiveproduction. [Int Microbiol 2013; 16(1):1-15]