Monday, August 13, 2012
Columbia Hall, Terrace Level (Washington Hilton)
The poly-3-hydroxybutyrate (PHB) is the most common type of polyhydroxyalkanoates (PHA) and its characteristics such as high cristallinity, stiffness, brittleness and low extension to break limit its application range. The mechanical and thermal properties of PHB can be improved by incorporating co-monomers like 3-hydroxyvalerate (3-HV). One factor that can lead to higher cost to PHA production is the cost of carbon feedstocks for bacterial cultures. Many agricultural and industrial byproducts have been considered for PHAs production and among them the biodiesel glycerol has becoming an interesting alternative. In this work, was utilized the Burkholderia cepacia isolated from Atlantic forest soil, at Ubatuba, SP, Brazil. The polymer production experiments were carried out by inoculating each test flask with 1.5ml of the nutrient broth culture in 50ml of mineral salts medium containing (g.l-1): (NH4)2SO4 0.2, 0.6, 1.0, 1.4 and 1.8; propionic acid 0, 0.5, 1.0, 1.5 and 2.0; and biodiesel glycerol 10, 15, 20, 25 and 30. The erlenmeyers flasks were incubated at 26.5, 30, 33.5 and 37°C with shaking at 150rpm for 72h. After incubation, the cells were harvested by centrifugation and lyophilized to a constant weight. The cell dry weight was determined gravimetrically. Glycerol and propionic acid was determined by liquid chromatography. Samples of about 10mg of freeze-dried cells were subjected to propanolysis for PHAs determination and the propyl esters were assayed by gas chromatography. B.cepacia showed maximum 3-HV yield at 25g.l-1 biodiesel glycerol and 0.5g.l-1 propionic acid (YHV/Prop=0.21g.g-1) with a PHA cellular productivity of 45.59% cell dry weight.