Functional metagenomics and chromosome engineering for enhanced bioplastics production

Bacterial production of polyhydroxyalkanoate (PHA) bioplastics has potential as a key part of the vegetable oil biorefinery. Production of PHA polymers with desirable characteristics must be optimized in order for bioplastics to compete with conventional plastics. We have developed functional metagenomic screens for novel PHA synthesis pathway genes. These screens are performed in Sinorhizobium meliloti and Pseudomonas putida, using broad host range cosmid soil metagenomic libraries that are available from the Canadian MetaMicroBiome Library (http://cm2bl.org). DNA sequence analysis indicates that a range of Class I and Class II PHA synthase encoding genes can be isolated using this approach. Expression of these genes in different host backgrounds such as S. meliloti, P. putida or Escherichia coli, facilitated by ΦC31-mediated chromosome engineering methods, results in differing quality and quantity of PHA product. We are also investigating the effects of carbon source and culture conditions on the final end product, with a focus on cultivation using oilseed derived feedstock. As a result of this work, we intend to be able to contribute towards the range and variety of PHA bioplastics that can be reliably produced.