Application of Experimental Design and Canonical Analysis of Response Surfaces to the Optimization of Poly(3-hydroxyalkanoates) Production by Pseudomonas aeruginosa 42A2

Many attempts to create bio-plastics from renewable resources have been made in recent years. The main aim of these studies has been to develop products competitive with synthetic polymers. Two main strategies have been studied to produce reasonable yields of these polymers: transgenic plant cells1 and the well known bacterial fermentation process.2 Among the various candidates for biodegradable polymers, polyhydroxyalkanoates (PHAs) have attracted considerable attention because of their similar properties to those of some common conventional plastics.3–5 PHAs are structurally accumulated as discrete intracellular cytoplasmic granules in bacterial cells as a result of the metabolic stress created by an unbalanced growth when an essential nutrient such as nitrogen, phosphorus, magnesium or oxygen is available only in limiting concentrations in the presence of excess carbon source.3,6,7 The main limitations in the production of PHAs are the special growth conditions required for the synthesis of the compounds, the difficulties involved in synthesizing them from inexpensive precursors and the high cost of their recovery.8 To reduce the production cost of medium-chain-length PHAs (mcl-PHAs), the use of media containing agro-industrial wastes such a palm-oil, molasses, whey, hemicellulose, corn, cassava, glycerol-rich biodiesel coproduct systems, meat-and-bone meal and ice cream residue, among others, have been studied.4,9–16 In this context, waste frying oils, sub-products from the vegetable oil refining process and linseed oil were used for the production of mclPHAs by Pseudomonas aeruginosa 42A2.11,17,18 However, the polymer content obtained with agro-industrial wastes is considerably lower than that obtained using purified carbon substrate. Therefore, there is a need to develop more efficient and appropriate bioprocess strategies for producing these polymers from cheap carbon sources.19–21 Thus, optimization of the fermentation medium is necessary and it has often been used to enhance the Application of Experimental Design and Canonical Analysis of Response Surfaces to the Optimization of Poly(3-hydroxyalkanoates) Production by Pseudomonas aeruginosa 42A2