project4

High-density microbial production of a biodegradable thermoelastomer

Poly-3-hydroxyalkanoates (PHAs) are a family of intracellular polyesters produced by a wide variety of microorganisms. They are water-insoluble, relatively resistant to aqueous hydrolysis and are readily biodegradable. They can be produced from renewable resources and are potentially recyclable. PHAs have mechanical properties similar to those of some common synthetic plastics. There are two major classes of PHAs: those whose polymeric units are predominantly five carbons or less are classified as short-chain-length PHAs (PHASCL) while all others are referred to as medium-chain-length PHAs (PHAMCL). Due to its longer side chain, PHAMCL has elastomeric properties. The latter materials have not been exploited due to technical difficulties in their production. The highest productivity of PHAMCL results from using octanoic or nonanoic acids . These substrates are relatively expensive and are toxic to the PHA-accumulating bacteria at concentrations of only several grams per Liter. The nitrogen source (ammonia) is also toxic at concentrations well below those needed to produce commercially viable high-density culture. Direct on-line analysis of substrate concentrations is not economically practical so toxicity avoidance is problematic. This project focuses on developing fermentation strategies to maximize the production of PHAMCL from relatively inexpensive and renewable resources such as canola oil. Canola oil will be converted into a suitable substrate and a feeding strategy developed and optimized for both the carbon and nitrogen sources such that these materials can be produced cheaply and efficiently.

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