Abstract

The polyhydroxyalkanoates (PHA) are polyesters produced by microorganisms as intracellular granules as source of carbon and energy. These materials arouse a great biotechnological interest, and confer thermoplastic and elastomeric properties similar to synthetic plastics, also it can be used for medical and industrial applications. In the biosynthesis of polyhydroxyalkanoates (PHA), the PHA synthase is the key enzyme for the incorporation of 3HA monomers into the polymer chain. The aim of this study was to evaluate the potential of different PHA synthases in adding different kinds of monomers to the polymer backbone, particularly short- and medium-chain-length monomers. The strains were two isolates (SCU 63 and SCU 66) able to produce expressive amounts of poly-3-hydroxybutyrate from glucose and octanoic acid. These isolates were identified as belonging to Burkholderia genus based on rDNA 16S gene. Primers were designed based on the adjacent DNA sequence of phaC genes (PHA synthase) from Burkholderia cepacia GG4 genomes available and used to amplify the phaC genes from SCU 63 and SCU 66. The phaC genes were cloned into the plasmid pBBR1MCS-2 and expressed in mutants of Burkholderia sacchari (LFM344) impaired in the accumulation of PHA. The recombinant strains were grown in excess glucose as carbon source in order to evaluate the potential of PHA synthase to incorporate monomers (3HA) to PHA. The recombinant strains of B. sacchari managed to accumulate PHA from 45% to 53% of dry cell mass, however, containing only 3-hydroxybutyrate (3HB) as a constituent, confirming that the cloned genes are functional. In another step, different fat acids will provided in order to evaluate the ability of the PHA synthases to incorporate other 3HA monomers different from 3HB (propionic, butyric, valeric and hexanoic acids).